Article

Facial hair whorls (trichoglyphs) and the incidence of motor laterality in the horse

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Several species demonstrate obvious motor laterality (sidedness, handedness) in their motor function. Motor laterality in the horse affects locomotion and subsequently equine performance during training and may have inherent safety implications for equitation. Some of the most commonly used identification features in the horse are hair whorls (trichoglyphs), since their specific location and character vary to some degree in every horse. We investigated the relationship between the hair flow of single facial hair whorls and the incidence of lateralised motor bias in 219 horses when under saddle in ridden work. The horses exhibited significant differences in motor preferences with 104 left-lateralised (LL) horses, 95 right-lateralised (RL) horses compared to only 20 well-balanced (WB) horses (chi(2)=36.9, d.f.=2, P<0.01). There was also a significant difference in the frequency distribution of single facial hair whorl patterns in the horses consisting of 114 horses with counter-clockwise (CC) whorls, 82 horses with clockwise (C) whorls and 23 horses, which had radial (R) whorls (chi(2)=38.87, d.f.=2, P<0.01). Overall there was a statistically significant association between motor behaviour and facial hair whorl patterns in the horses (chi(2)=69.4, d.f.=4, P>0.001). The RL horses had significantly more C facial hair whorls and the LL horses had significantly more CC facial hair whorls than would be expected purely by chance alone (P<0.05). The findings may provide trainers with a useful tool when attempting to identify simple, non-invasive and reliable predictors of motor laterality in the horse. Furthermore, given that efficient targeted training of performance horses during ridden work may produce WB equine athletes, the findings could assist trainers when designing individual-specific training programmes for young horses.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Motor laterality has been determined by observing the preferred advanced forelimb during foraging either on pastures (32)(33)(34)(35) or with standardized preference tests (36, 37), by documenting the preferred limb for the initiation of movement (38) or truck loading (39), the preferred lead during flat racing (40), as well as the preferred turning side to avoid obstacles (38), the preferred side to roll on (38) and the lateral derailment of the hindquarters while standing (41) or trotting on a circle (42) in foals and young horses. Laterality, as assessed by the riders (43)(44)(45) or by experimenters based on judge's scores during competitions (46, 47), has been evaluated. However, other test methods have rarely been investigated for agreement with laterality during riding or among each other, and agreement between studies was limited (36, 38). ...
... Even though motor laterality has been observed in foals, too (36, 42), the majority of young horses seem to be ambidextrous (32,36,42). Motor laterality in horses might be left-biased (32,33,44) based on, e.g., leg preferences for grazing or initiating movement, but right-biased during riding (49)(50)(51). Results varied for the main direction of laterality overall (32) and between different breeds such as Standardbreds, Quarter Horses, Thoroughbreds, or feral horses (21,33,34). ...
... If the hindquarters were displaced to the right, the values were assigned a negative sign, while values from displacements to the left were assigned a positive sign, resulting in a continuous variable. -(8) (RiderAssessment) Horse's laterality was assessed by their riders as previously described by Murphy and Arkins (44), i.e., riders were asked to name the preferred or more supple side for dressage tasks and turns, and horses were classified as left-lateral, right-lateral, or ambidextrous accordingly (Applied to sample A1). -(9) (ReinTensionMean; ReinTensionSD) Rein tension patterns (mean rein tension and mean SD) were investigated for associations between rein tension symmetry and laterality in relation to the direction of movement (clockwise vs. counter-clockwise) as previously described by Kuhnke et al. (56) in order to find out whether differences between asymmetric rein tension of right-handed riders with left-and right-lateral horses can be observed with left-handed riders and different directions of laterality in their horses as well (Applied to sample A2). ...
Article
Full-text available
The present study aimed to assess an agreement between established and novel methods to determine laterality and to identify the distribution of laterality in warmbloods and Thoroughbreds. Nine different methods to investigate a horses' laterality outside a riding context and during riding were compared across two groups of horses (sample A: 67 warmblood- type horses, sample B: 61 Thoroughbreds). Agreement between any two methods was assessed by calculating Cohen's kappa with McNemar's test or Bowker's Test of Symmetry, and the deviation from equal distributions was assessed with chi²-tests. Continuous variables such as rein tension parameters were analyzed using ANOVA or linear mixed models. Generally, laterality test results obtained outside a riding context did not agree with laterality during riding or among each other (Bonferroni corrected p > 0.0018). However, the rider's assessment of her/his horse's laterality allowed conclusions on rein tension symmetry (p = 0.003), and it also agreed substantially with the lateral displacement of the hindquarters (p = 0.0003), a method that was newly developed in the present study. The majority of warmbloods had their hindquarters displaced to the right (73.1%, X² = 14.3; p < 0.0001). The pattern of lateral displacement of the hindquarters was similar in the Thoroughbred sample (right: 60.7%, left: 39.3%), but did not deviate significantly from an equal distribution (X² = 2.8; p > 0.05). Laterality seems to be manifested in different ways, which generally are not related to each other. Attention should be paid to the desired information when selecting methods for the assessment of laterality. Horses' laterality has an impact on the magnitude and symmetry of rein tension. Matching horses and riders according to their laterality might be beneficial for the stability of rein tension and thus improve training.
... In horse lore, patterns of hair-whorls have been correlated with temperament (Forsberg, 2008). In a formal study, patterns of hair-whorls have been correlated with equitation manoeuvres (Murphy & Arkins, 2008). Our interest in hair-whorls stems from our novel observation that a pronounced hair-whorl feature, the horse's mane, is asymmetrical with more horses having right-sided mane than leftsided mane (Kolb & Whishaw, personal observations AQ5 ¶ ...
... We were also surprised by the large sex difference in the proportion of horses displaying a right mane direction bias. Although the relation between hair-whorl direction and sex has been examined in other studies, the main finding is that female horses are less asymmetric than male horse (Murphy & Arkins, 2008) rather than more asymmetric, as is reported here. ...
... In summary, our finding of no relation between mane direction and performance is a robust finding. The absence of a relationship between mane direction and equitation performance does not exclude the possibility of other hair-whorl and performance relations, such as those reported by Murphy and Arkins (2008). In the Murphy and Arkins study, asymmetric performance was evaluated by the riders of the horses and not by independent judges. ...
Article
Full-text available
A human physical asymmetry is the near 90% clockwise occipitoparietal scalp hair-whorl direction in Europeans, an incidence that approximates the left lateralization of speech and right-handedness. Hair-whorl direction is also asymmetric in horses, Equus ferus caballus and placement is proposed to be related to temperament and lateralized skill in equitation manoeuvres. We describe a hair-whorl asymmetry in the horse, mane direction. Of 526, 3-year-old American Quarter horses, 69% of horses had mane directed to the right and 31% had mane directed to the left. The bias was larger in females, with 74% of females vs. 65% of males having mane directed to the right. Mane direction was unrelated to coat colour. The behavioural significance of mane asymmetry was investigated using judges' scores from a reining competition requiring symmetrical maneuvers of spin, circle and roll-back to either the left or to the right. There was no relation between mane asymmetry and overall reining performance and no relation between mane direction and scores for left or right manoeuvres. The results are discussed in relation to the significance of morphological asymmetries, neural function and the influence of planar cell polarity genes, such as Frizzled, that influence epidermal hair cell patterning.
... In horses, the vertical and lateral position, number, and direction of the growth of hair whorls on the head have been associated with behavior, with temperament is the hair whorl. In horses, the vertical and lateral position, number, and direction of the growth of hair whorls on the head have been associated with behavior, temperament, and laterality [3][4][5][6]. This association has been attributed to the fact that the epidermis and nervous system have the same embryonic origin [7]. ...
... This is the first GWAS of hair whorl traits in domestic animals, using horses as a study model. Hair whorl traits are used as indicators of behavior in horses [3][4][5][6]. The genetic architecture of these traits was very similar, with few genomic regions explaining much of the additive genetic variance in the traits. ...
Article
Full-text available
The position and number of hair whorls have been associated with the behavior, temperament, and laterality of horses. The easy observation of whorls assists in the prediction of reactivity, and thus permits the development of better measures of handling, training, mounting, and riding horses. However, little is known about the genetics involved in the formation of hair whorls. Therefore, the aim of this study was to perform a genome-wide association analysis to identify chromosome regions and candidate genes associated with hair whorl traits. Data from 342 Quarter Horses genotyped for approximately 53,000 SNPs were used in an association study using a single-step procedure. The following traits were analyzed: vertical position of hair whorl on the head, number of whorls on the head, and number of whorls on the left and right sides of the neck. The traits had between one and three genomic windows associated. Each of them explained at least 4% of the additive variance. The windows accounted for 20–80% of additive variance for each trait analyzed. Many of the prospected genes are related to hair follicle growth. Some of these genes exert a pleiotropic effect on neurological and behavioral traits. This is the first indication of biological and physiological activity that might explain the association of hair whorls and temperament.
... It was suggested that the whorl directions could be an indicator of behavioral motor performance in horses, and facial hair whorl pattern was correlated with sidedness in horses (Swinker, Deesing, Tanner, & Grandin, 1994). Murphy and Arkins (2008) assessing the association between horse laterality function (left-lateralized, rightlateralized and well-balanced) and facial whorl direction (clockwise, counterclockwise and radial). The whorl direction was assessed by the direct inspection while the laterality examined according to functional motor features including foreleg initiated forward motion, obstacle avoidance in a limited passageway and motor rolling preference. ...
... The whorl direction was assessed by the direct inspection while the laterality examined according to functional motor features including foreleg initiated forward motion, obstacle avoidance in a limited passageway and motor rolling preference. They found a significant relationship between being leftlateralized and counterclockwise whorl direction in horses (Murphy & Arkins, 2008). In another study made on small group horses, the association between whorl phenotype (height, location and swirling style on facial region) and behavioral motor responses (turning right or left) to a fearful stimulus performed by an umbrella was evaluated (Shivley, Grandin, & Deesing, 2016). ...
Article
Full-text available
Hair whorl direction and handedness were stated to have a common genetic basis in the random recessive model. This study was carried out with a total of 317 healthy young males. The association between hair whorl swirling direction and handedness, footedness and eyedness were assessed. The direction of hair whorl was clockwise at a rate of 76.7%, and counter clock wise at a rate of 23.3%. There was no significant association between hair whorl direction and handedness, footedness, and eyedness (p > .05). The results indicate that hair whorl swirling direction is not an evident marker of functional laterality.
... and performance; these factors were not considered in our study. However, sex differences have been associated with equine laterality previously (McGreevy and Rogers, 2004;Murphy and Arkins, 2008); lateralisation of the horse is linked to cerebral hemispheric lateralisation and, therefore, a link could exist between motor laterality, pinna symmetry and brain lateralisation. An almost equal split of PDA and NDA was demonstrated for nostril width within all three groups. ...
... The additional compressive strain on the shorter left limb would result in thickening of the bone over time due to remodelling of this dynamic structure, again reflecting the wider bone dimensions seen within the current study. Lateralisation may be determined in utero (Murphy and Arkins, 2008) and has been suggested, alongside gait habits, to Asymmetry (mm) Fig. 2. Asymmetry means including standard deviation for the functional (limb) traits of the pooled, horse and pony groupings for both the positive and negative directional asymmetry categories. FPP, fore proximal phalanx; HPP, hind proximal phalanx; MCIII, metacarpal III; MTIII, metatarsal III. ...
... It has been proposed that in multi species, temperament (Grandin 1998: Lanier et al. 2001, sexual orientation (Rahman et al. 2009), lateralization (Weber et al. 2006 ;Murphy & Arkins 2008), learning ability (Broucek et al. 2004) and brain development (Samlaska et al. 1989) can be identified by the position and direction of the hair whorls. ...
... In modern equitation, demands are put on the horse that interferes with their asymmetry and natural movement. The major significance of balance in horses is recognised in the preparation of horses for various sports (Murphy & Arkins 2008). In many equestrian disciplines, it is important that horses exhibit the same level of balance on both sides (Wells & Blache 2005) and performance may be impaired or enhanced by their laterality (Randle & Elworthy 2005). ...
... In most studies related to equine laterality, the majority of horses were left-biased [15][16][17] . The use of the horse's left eye was found to correlate with higher reactivity 18,19 and negative emotional reactions 20 . ...
... It is an important aim in most riding theories to adjust the horse's 'natural crookedness' towards a symmetric pattern of movement. Still, even advanced dressage horses are often unbalanced 17,24 , and laterality-related problems are noted by riders at all levels 28 . ...
Article
Full-text available
The purpose of the present study was to investigate the effect of the horse's laterality on the symmetry of rein tension in right-handed riders. Eleven right-handed riders rode both a right-lateralized (RL) and a left-lateralized (LL) horse. Rein tension was measured during three circles of walk, trot and canter and four walk–halt transitions in each direction. Tensions were recorded continuously using a rein tension meter. The LL horse was ridden with significantly stronger mean tension in the left rein than in the right rein (1.5 vs. 1.4 kg; P = 0.0352). Significantly more tension was applied to the outside rein in a clockwise (1.4 vs. 1.2 kg; P = 0.0202), but not in a counterclockwise, direction (1.3 vs. 1.2 kg; P = 0.49). Less minimum tension (0.06 vs. 0.29 kg) and greater maximum (6.4 vs. 3.9 kg) and range of tension (6.3 vs. 3.6 kg) occurred in the left rein of the RL horse (P < 0.0001) and the right rein of the LL horse (0.37 vs. 0.08 kg, 4.8 vs. 7.4 kg, 4.3 vs. 7.3 kg respectively; P < 0.0001). The results of the present study indicate that the different utilization of both reins is likely to be influenced by the laterality of both horse and rider. These findings may have important implications for equine training, since consistency of reinforcement is an important factor for equine learning success.
... Related studies in non-human animals have largely focused on relationships between forehead (cephalic) whorl position and temperament (Grandin et al., 1995;Randle, 1998;Lanier et al., 2001;Górecka et al., 2006), but have not assessed whorl direction. More recently, Murphy and Arkins (2008) reported an association between cephalic hair whorl direction and reported motor laterality in horses, with counterclockwise whorls occurring in 52% of horses and being significantly linked with a left-motor bias during ridden work. Hair whorl characteristics in Canidae have not widely been assessed prior to this two-part study (see Tomkins and McGreevy, in press). ...
... The relationship between whorl direction and behavioral characteristics has not widely been established in non-human animals, and even where studies have been conducted, such as that by Murphy and Arkins (2008) in the horse, only cephalic whorls were studied. By describing the distribution of whorl direction in the 10 different regions of the dog, a clearer understanding of whorls can be ascertained in the domestic dog, with the current data offering the potential to facilitate exploration of the relationship between laterality and hair whorl characteristics. ...
Article
In horses and cattle, hair whorls have been shown to act as a structural marker of reactivity and behavioral lateralization. Few studies on canine whorls have been reported and none have assessed whorl position or direction of flow. This study describes the distribution and characteristics of whorl in each of 10 regions in which whorls are typically located in dogs. Hair whorls were assessed in dogs (n = 120) and were recorded as clockwise or counterclockwise in the cephalic, cervical (dorsal, lateral, ventral), thoracic and brachial axillary, chest, shoulders, elbows, abdominal, and ischiatic regions. Bilateral whorls, including brachial axillary, elbow, abdominal and ischiatic whorls, rotated in opposing directions, allowing the dog's overall hair coat to be symmetrical. Cephalic, brachial axillary, and ischiatic whorls were consistent in their direction; cephalic and ischiatic whorls were clockwise on the right side of the body, and counterclockwise on the left, whereas right brachial axillary whorls were counterclockwise and left were clockwise. The central chest whorl was predominantly counterclockwise (91.21%). Direction of whorls was associated with several factors, including coat length, coat thickness, sex and source of the dog.
... Funkčnost smyslových orgánů se zřejmě odráží na pozici chlupových vírů. V případě vady smyslových orgánů se čelní chlupový vír posouvá blíže k funkčnímu orgánu (Murphy 2008). Tyto poznatky umožňují předvídat reakce a chování koně (Górecka et al., 2006). ...
... Numerous papers have studied the relationship between body conformation, coat color or coat particularities and temperament traits in domestic animals [1][2][3][4][5][6][7][8]. Among the particularities which have been studied in greater depth are hair whorl patterns [5,[9][10][11][12]. These hair features, also called trichoglyphs, are laid down between the 10th and the 16th weeks in utero in humans and can act as an indicator of abnormal cerebral development [13]. ...
Article
Full-text available
Simple Summary Hair whorls in horses are a hereditary trait that may be associated with various factors, including the temperament or the coat color of the animals. Hair whorls are described as changes in the hair pattern and may take various forms: circular whorls (spirals of hair with a round epicenter) and linear whorls (a line where the hairs span out on both sides from the center, producing an oval shape similar to a feather). The aim of this study is to estimate the frequency and genetic parameters of the number and position of circular and linear hair whorls (on head, body-neck and limbs) of the Pura Raza Española horse according to different factors such as gender, level of inbreeding, birth period and coat color. In this breed, circular whorls are more prevalent than linear whorls, with both showing a relevant symmetry. The laterality of hair whorls has been also evidenced and are most concentrated on the left-hand side. Most horses, particularly gray ones, showed circular hair whorls below the central line of the eyes; in a previous paper, this was associated with a calmer and more docile temperament. Hair whorls have medium-high heritability and can be included in a breeding program due to their relationship with behavior. Abstract Hair whorls are a hereditary feature in horses that may be associated with temperament and coat color. Hair whorls are described as changes in the hair pattern and may take various forms, such as circular and linear whorls. We first carried out a frequency analysis of hair whorls (circular and linear). Next, a Generalized Non-Linear Model was computed to assess the significance of some potential influencing factors, and a genetic parameter estimation was performed. ENDOG software v4.8 was used to estimate the inbreeding coefficient of all the animals analyzed. It was more common to find horses with circular hair whorls than with linear whorls. The heritability ranges obtained were, in general, medium-high for both circular whorls (0.20 to 0.90) and linear whorls (0.44 to 0.84). High positive correlations were found on the between left and right positions, indicating a tendency to symmetry in certain locations. The laterality of hair whorls was also evidenced, with the biggest concentration on the left-hand side, particularly in gray horses, showing circular whorls below the central line of eyes, which has been associated in a previous paper with a calmer and more docile temperament.
... While scientists and equestrians agree that motor laterality is likely to be present in horses, at least to some extent, the pattern of asymmetries described overlap only partially between equestrians' perceptions and the scientific literature. Equestrians frequently describe a difference in the horse's ability to turn in left vs. right direction (Murphy & Arkins, 2008;Kuhnke et al., 2010;Kuhnke & König von Borstel, 2022). One side is described as the "hollow" side based on the horse bending more easily towards that side and the other side described as the "stiff" side due to the horse's reluctance to bend towards that side . ...
Article
Full-text available
Background Horses commonly show asymmetries that manifest as left (L)-right (R) differences in vertical excursion of axial body segments. Moving on a circle confounds inherent individual asymmetries. Our goals were to evaluate individual and group asymmetry patterns and compare objective data with subjective impressions of side preference/laterality in horses walking on L and R circles. Methods Fifteen horses walked on L and R circles unridden and ridden on long and short reins. Optical motion capture (150 Hz) tracked skin-fixed markers. Variables were trunk horizontal angle; neck-to-trunk angle; vertical range of motion (ROM) for the head, withers and sacrum; ROM for pelvic roll, pitch, and yaw; mean pelvic pitch; and ROM for hip, stifle and tarsal joints. Differences between inside and outside hind steps were determined for vertical minima and maxima of the head (HMinDiff/HMaxDiff), withers (WMinDiff/WMaxDiff) and sacrum (PMinDiff/PMaxDiff). Subjective laterality was provided by owners. Data analysis used mixed models, first without and then with subjective laterality. Iterative k-means cluster analysis was used to associate biomechanical variables with subjective laterality. Results PMaxDiff, PMinDiff and WMaxDiff indicated R limb asymmetry in both directions. WMinDiff indicated L (inside) fore asymmetry for L direction but was close to zero for R direction. Hip ROM was significantly smaller for the inside limb in both directions (L inside/outside: 16.7° vs . 20.6°; R: 17.8° vs . 19.4°). Stifle ROM was significantly larger for the inside limb in both directions (L: 43.1° vs . 39.0°; R: 41.9° vs . 40.4°). Taking the general direction effect into account the R hip and L stifle had larger ROM. Adding laterality to the models (seven horses L- vs . six horses R-hollow), PMaxDiff R hind asymmetry was more obvious for L-hollow horses than for R-hollow horses. L-hollow horses had greater pelvic roll ROM moving in L vs . R direction. L-hollow horses had smaller inside and greater outside hip joint ROM in L vs . R direction. R-hollow horses had a significant difference in HMinDiff between L (0 mm) and R (−14 mm) directions, indicating less head lowering at outside forelimb midstance in R direction, and larger outside tarsal ROM in R (38.6°) vs . L (37.4°) direction ( p ≤ 0.05). The variables that agreed most frequently with subjective laterality in cluster analysis were pelvic roll ROM, followed by HMinDiff and PMaxDiff. Conclusion Differences between horses walking in L and R directions were found both at group and individual levels, as well as evidence of associations with subjective laterality. Horses maintained more symmetric hip and stifle ROM and withers vertical motion when walking on the R circle. Findings suggest that left and right lateralised horses may not be perfect mirror images. Pelvic roll ROM emerged as a promising variable to determine laterality in walk as perceived by the rider, especially when considered together with other variables.
... Motor laterality has been often studied in non-human animals, including ungulates [1][2][3] . These studies have relied on the use of different scenarios, including leg positions while standing or resting, leg movement associated with locomotion, grazing/foraging behavior, contest, splaying, and suckling behavior, as well as unrestricted food handling 4-6 . ...
Article
Full-text available
Motor laterality has been often studied in non-human animals, including ungulates, and it has been noted that adult animals tend to be ambidextrous. Therefore, the current study aimed to study the laterality of grazing posture when standing in a quadrupedal position. To this end, a total of 106 horses (24 foals, 8 yearlings, 14 subadults and 60 adults 53 females and 7 males) of Pyrenean horse from 11 grazing areas farms were observed and their forelimb preference when grazing was recorded (1-3 times for each animal). The obtained results revealed that approximately half of the horses were right-handed and half left-handed, and females were equally lateralized than males. Moreover, lateralization was not affected by age. Therefore, it seems that forelimb ambidexterity in Pyrenean horses is probably due to the lack of human contact. As the presentation of unevenness may be crucial to orthopaedic health and the compensatory mechanisms used by uneven footed horses are currently unknown, data presented here have a complementary crucial interest.
... The results of studies on motor laterality in horses are inconclusive and often conflicting, which may suggest that there is no objective method of assessing limb laterality in this species (20). At the same time, researchers agree that the issue of motor laterality is particularly important in these animals, as it has implications for the athletic performance of horses, understanding their predispositions as well as for horse welfare and human safety (24,31,38). ...
Article
Full-text available
The third metacarpal (MC3) bone, along with the proximal phalanx, is one of the bones that are most prone to injury in sport horses. To date, no detailed analysis has been conducted that would compare the strength parameters of bilateral MC3 bones taking into account differences depending on the site of measurement. The aim of the study was to compare strength parameters between the left and right MC3 bones in horses at 10%, 20%, 30%, 40%, 50%, 60%, 70% and 80% of the bone length using peripheral quantitative computed tomography (pQCT). The research material comprised isolated bilateral MC3 bones from 21 horses (age range: 3-27 years). The structure of these bones was measured using high-resolution pQCT. The following bone parameters were determined: polar strength strain index, strength strain index X and strength strain index Y. The computed tomographic analysis of the MC3 bones was carried out at sections from 10% to 80% (every 10%) of the bone length. The statistical analysis showed that in most cases the strength parameters calculated using pQCT were significantly higher for the right MC3 bones at 10%, 20% and 50% of the bone length, i.e. at the proximal metaphysis and at the proximal diaphysis. However, strength parameters measured at 60% and 80% of the diaphyseal length, i.e. at the distal diaphysis, were significantly higher for the left MC3 bones. Further studies of the MC3 bones parameters should focus on the vicinity of the proximal metaphysis and at the proximal diaphysis.
... It would, therefore, seem appropriate to take motor and sensory laterality into consideration as indicators for increased stress [18]. Laterality also has safety implications, as strongly lateralised horses may show strong reactions to a stimulus, which could result in flight and endanger the animal as well as the rider or handler [20,74]. ...
Article
Full-text available
For centuries, a goal of training in many equestrian disciplines has been to straighten the horse, which is considered a key element in achieving its responsiveness and suppleness. However, laterality is a naturally occurring phenomenon in horses and encompasses body asymmetry, motor laterality and sensory laterality. Furthermore, forcibly counterbalancing motor laterality has been considered a cause of psychological imbalance in humans. Perhaps asymmetry and laterality should rather be accepted, with a focus on training psychological and physical balance, coordination and equal strength on both sides instead of enforcing “straightness”. To explore this, we conducted a review of the literature on the function and causes of motor and sensory laterality in horses, especially in horses when trained on the ground or under a rider. The literature reveals that body asymmetry is innate but does not prevent the horse from performing at a high level under a rider. Motor laterality is equally distributed in feral horses, while in domestic horses, age, breed, training and carrying a rider may cause left leg preferences. Most horses initially observe novel persons and potentially threatening objects or situations with their left sensory organs. Pronounced preferences for the use of left sensory organs or limbs indicate that the horse is experiencing increased emotionality or stress, and long-term insufficiencies in welfare, housing or training may result in left shifts in motor and sensory laterality and pessimistic mentalities. Therefore, increasing laterality can be regarded as an indicator for insufficiencies in housing, handling and training. We propose that laterality be recognized as a welfare indicator and that straightening the horse should be achieved by conducting training focused on balance, coordination and equal strength on both sides.
... In our study, unfortunately, we were able to collect only one questionnaire per horse. We also did not nd any correlation between behavioural responses and hair swirls position, an association suggested previously (7,11,37). ...
Preprint
Full-text available
We tested 35 Lipizzan horses older than five years, ridden and healthy in three behavioural tests (handling, fear-reaction, and learning ability test). Physiological (heart rate and heart rate variability) and anatomical measurements (120 head and body distances and angles) were collected to validate parameters that reliably inform on fear/exploration and learning ability in horses. Utilizing a standard clustering methodology on the behavioural data, we identified four general types of responses and categorised an individual as intermediate, low fearful, hard to handle or with low learning ability. We additionally analysed the head morphology following Tellington-Jones and Taylor recommendations and correlated the measurements with data from a horse personality questionnaire. Although allocation to a particular personality group was not associated with these two methods, these groups differed in six anatomical characteristics of head and body. Regardless of the group, our results indicated that shorter horses (˂75.9 cm) with a wider muzzle (˃10.5 cm) are trustworthy, less fearful and easier to handle and train. We also demonstrated that horses with stronger legs and a wider base of the head have a lower heart rate when exposed to the second trial of the handling test.
... Motor laterality has been found among foals and unhandled youngsters (Drevemo et al., 1987;Van Heel et al., 2006), and seems to increase with age, when derailment (Lucidi et al., 2013) and forelimb preference while eating from the ground (McGreevy and Thomsen, 2006, Van Heel et al., 2010 were studied. Expressions of laterality have also been found to vary with breed (McGreevy and Thomsen, 2006;Williams and Norris, 2007), sex (Murphy and Arkins, 2008;Murphy et al., 2005), training and handling (Drevemo et al., 1987;McGreevy and Rogers 2005), acute stress (Siniscalchi et al., 2014), and high vs low rectangular body shape (Van Heel et al., 2010). However, associations between limb preference and behavioural/emotional expressions of laterality and asymmetry of gait have not been conclusively shown (Austin and Rogers, 2012;McGreevy and Rogers, 2005;Siniscalchi et al., 2014). ...
Article
Full-text available
It has been suggested that one of the underlying causes of asymmetrical performance and left/right bias in sound riding horses is laterality originating in the cerebral cortices described in many species. The aim of this paper is to review the published evidence for inherent biomechanical laterality in horses deemed to be clinically sound and relate these findings to descriptions of sidedness in equestrian texts. There are no established criteria to determine if a horse is left or right dominant but the preferred limb has been defined as the forelimb that is more frequently protracted during stance and when grazing. Findings on left-right differences in forelimb hoof shape and front hoof angles have been linked to asymmetric forelimb ground reaction forces. Asymmetries interpreted as motor laterality have been found among foals and unhandled youngsters, and the consistency or extent of asymmetries seems to increase with age. Expressions of laterality also vary with breed, sex, training and handling, stress, and body shape but there are no studies of the possible link between laterality and lameness. In a recent study of a group of seven dressage horses, a movement pattern in many ways similar to descriptions of sidedness in the equestrian literature, e.g. one hind limb being more protracted and placed more laterally than the other, has been documented. The role of innate laterality versus painful conditions, training, human handedness and simply habit remains to be determined. Understanding the biomechanical manifestations of laterality in healthy horses, including individual variation, would yield a potential basis for how laterality should be taken into account in relation to training/riding and rehabilitation of lameness.
... Although the effects of sex have been reported in 24 studies, only 8 of these actually found effects ( Table 2). For instance, female horses were found to be right-biased in several motor functions, while males were left-biased in the same functions [63,64], and female pigs viewed their opponent more with the right eye during aggressive displays, while males more often used the left eye in this context [172]. These findings are therefore in line with the general trend in mammals. ...
Article
Full-text available
In functional laterality research, most ungulate livestock species have until recently been mainly overlooked. However, there are many scientific and practical benefits of studying laterality in ungulate livestock. As social, precocial and domestic species, they may offer insight into the mechanisms involved in the ontogeny and phylogeny of functional laterality and help to better understand the role of laterality in animal welfare. Until now, most studies on ungulate livestock have focused on motor laterality, but interest in other lateralized functions, e.g., cognition and emotions, is growing. Increasingly more studies are also focused on associations with age, sex, personality, health, stress, production and performance. Although the full potential of research on laterality in ungulate livestock is not yet exploited, findings have already shed new light on central issues in cognitive and emotional processing and laid the basis for potentially useful applications in future practice, e.g., stress reduction during human-animal interactions and improved assessments of health, production and welfare. Future research would benefit from further integration of basic laterality methodology (e.g., testing for individual preferences) and applied ethological approaches (e.g., established emotionality tests), which would not only improve our understanding of functional laterality but also benefit the assessment of animal welfare.
... Different horse breeds are reported to have variable individual and population handedness [11]. There are also differences in and between populations due to age [12], sex [13,14], training, handling, breeding [15], arousal [16,17], and morphological proportions [18]. ...
Article
Full-text available
Laterality can be observed as side biases in locomotory behaviour which, in the horse, manifest inter alia as forelimb preferences, most notably in the gallop. The current study investigated possible leading-leg preferences at the population and individual level in Thoroughbred racehorses (n = 2095) making halt-to-gallop transitions. Videos of flat races in the UK (n = 350) were studied to record, for each horse, the lead-leg preference of the initial stride into gallop from the starting stalls. Races from clockwise (C) and anti-clockwise (AC) tracks were chosen alternately at random to ensure equal representation. Course direction, horse age and sex, position relative to the inside rail and finishing position were also noted. On C courses, the left/right ratio was 1.15, which represents a significant bias to the left (z = –2.29, p = 0.022), while on AC courses it was 0.92 (z = 0.51, p = 0.610). In both course directions, there was no significant difference between winning horses that led with the left leading leg versus the right (C courses, z = –1.32, p = 0.19 and AC courses, z = –0.74, p = 0.46). Of the 2,095 horses studied 51.26% led with their L fore and 48.74% with their R, with no statistically significant difference (z = -1.16, p = 0.25). Therefore, there was no evidence of a population level motor laterality. Additionally, 22 male and 22 female horses were randomly chosen for repeated measures of leading leg preference. A laterality index was calculated for each of the 44 horses studied using the repeated measures: 22 exhibited right laterality (of which two were statistically significant) and 21 exhibited left laterality (eight being statistically significant); one horse was ambilateral. Using these data, left lateralized horses were more strongly lateralized on an individual level than the right lateralized horses (t = 2.28, p = 0.03, DF = 34) and mares were more left lateralized than males (t = 2.4, p = 0.03, DF = 19).
... Different horse breeds are reported to have variable individual and population handedness [11]. There are also differences in and between populations due to age [12], sex [13,14], training, handling, breeding [15], arousal [16,17], and morphological proportions [18]. ...
... Initially thought to be uniquely human (Corballis & Beale, 1983), these behavioral asymmetries have been demonstrated in a variety of different species and may be a characteristic of all vertebrates (e.g., Vallortigara, Chiandetti, & Sovrano, 2011;Versace & Vallortigara, 2015;Wells, 2003) with evidence for lateralization also being found in invertebrates (see Frasnelli, Vallortigara, & Rogers, 2012 for review). Examples of behavioral lateralization are broad; primates will more commonly use a specific hand for object manipulation (e.g., Chapelain, 2010), blue gourami (Trichogaster trichopterus) initially touch novel objects more often with their left fin (Bisazza, Lippolis, & Vallortigara, 2001), grey whales (Eschrichtius robustus) benthic forage more frequently with one side of their mouths (Woodward & Winn, 2006), dolphins exhibit asymmetries with listening response (Au, 1993;Au & Benoit-Bird, 2003), horses (Equus ferus caballus) tend to lead with a preferred foot (Murphy & Arkins, 2008), psittaformes and corvids tend to hold and manipulate food with a specific foot (Rogers, 2007), rodents and felines tend to reach towards objects with a preferred paw (e.g., Warren, 1980), and dogs show both an asymmetry with paw preferences (Berta, 2011) as well as tail-wagging when responding to varying stimuli (Quaranta, Siniscalchi, & Vallortigara, 2007). While hypotheses have been made as to the benefits of consistent behavioral lateralization, such as increasing brain efficiency to multitask (e.g., Rogers, Zucca, & Vallortigara, 2004), or increased social coordination (e.g., Ghirlanda & Vallortigara, 2004;Vallortigara & Rogers, 2005), some evidence suggests that asymmetric populations also receive benefits from the lack of uniform lateralization (Ghirlanda, Frasnelli, & Vallortigara, 2009). ...
Article
Full-text available
The preference for utilizing certain appendages (handedness) has been explored in a variety of vertebrate species. Similar to primates, dolphins possess hemispheres that allow an individual to present behaviorally dominant features and appendages (i.e., pectoral fins) that are utilized both as social facilitators, as well as means to interact with objects. Thus, the possibility of handedness in a captive population of 27 bottlenose dolphins (Tursiops truncatus) was explored. Dolphins in a mother-offspring relationship made significantly more pectoral fin contacts than in the absence of this relationship. No significant difference was observed between maternal siblings and non-maternal siblings in overall pectoral fin contact. Handedness indexes were calculated for 26 individuals that initiated pectoral fin contact with both conspecifics and flora (i.e., seagrass) in their habitat. No significant differences were observed between the sexes in handedness indexes; however calves displayed a significant right-fin handedness compared to both sub-adults and adults. Both subadults and adults showed a left-fin handedness indexes, but no significant difference in the strength of this relationship among these two age classes was observed. Individual variation in handedness indexes was also noted. These results suggest that handedness may be present in Atlantic bottlenose dolphins with regards to social contact, and a larger and more diverse sample size may provide a better understanding in why handedness may change across development.
... Visual and motor lateralization are important features for locating food, hunting, auditory vigilance and social and reproductive surveillance. Lateralization is associated directly with asymmetry of the brain hemispheres (Csermely 2013) and horses exhibit left lateralization (Murphy and Arkins 2008). We found no difference between the left and right pairs of the nerves that innervate the extraocular muscles. ...
Article
We investigated the microscopic structure of transverse sections of the oculomotor, trochlear and abducens nerves of Arabian foals using stereological methods. Bilateral nerve pairs from 2- month-old female Arabian foals were analyzed. The tissues were embedded in plastic blocks, then 1 μm thick sections were cut and stained with osmium tetroxide and methylene blue-azure II. Stereology was performed using light microscopy. Morphometry showed that the right and left pairs of nerves were similar. The transverse sectional areas of the oculomotor, trochlear and abducens nerves were 1.93 ± 0.19 mm2, 0.32 ± 0.06 mm2 and 0.70 ± 0.08 mm2, respectively. The oculomotor nerve exhibited a significantly greater number of myelinated axons (16755 ± 1279) and trochlear (2656 ± 494) and the abducens nerves (4468 ± 447). The ratio of the axon diameter to myelinated nerve fiber diameter was 0.58, 0.55 and 0.55 for the oculomotor, trochlear and abducens nerves, respectively. Of the three nerves studied, the abducens nerve exhibited the greatest nerve fiber area, myelin area, nerve and axon diameters, and myelin thickness. The ratio of small myelinated nerve fibers was greatest in the oculomotor nerve.
... These cows pay more attention to their surroundings and they perceive threats earlier [7]. In horses, there is an association between the facial HW and motor behaviors [16]. Horses with a spiral HW that turns counter-clockwise tend to be left-lateralized and horses with clockwise HW are more likely to be right-lateralized. ...
... years, range 3-11 years, variable colour and a gender distribution of 15 (71.43%) geldings and 6 (28.57%) mares. A facial dermatoglyph profile was produced for each horse utilising previously validated methods (Murphy & Arkins, 2008). Individual trichoglyphs ( Figure 1) were photographed, by the same experimenter, using a 10.2 mega-pixel Canon 400D digital camera (Adobe Photoshop: version 9.2) to enable remote analysis. ...
Article
Full-text available
The influence of equine facial dermatoglyphic profiles on English and Irish Thoroughbred (Equus caballus) flat racehorse performance ratings - Volume 1 Issue 1 - J M Williams
... To date, research studies have suggested that most humans (Corballis, 1989;Symes and Ellis, 2009) and horses (McGreevy and Rogers, 2005;Murphy and Arkins, 2008) exhibit mild bilateral asymmetry/laterality. This may be inherent or as a consequence of previous injury, pathology, or differential musculoskeletal development. ...
Article
It is commonplace for trainers and judges to comment that riders are “crooked” or “collapsed in the hip.” This asymmetrical posture will likely have a significant effect on stability/balance and may subsequently have a detrimental effect on performance. Although the effects of asymmetry on athlete performance has received much attention on human-only sports, there has been little scientific research investigating the influence of these factors in equestrianism, despite anecdotal acknowledgment that “a good seat” and core stability has strong influence on the horse and that crookedness may contribute to high incidences of back pain in both the rider and horse. Asymmetry among athletes has been shown to lessen after physiotherapy intervention (PI).This study examined whether the effect of PI to a group of experienced riders improved seated postural stability (determined as the root mean square [RMS] of the center of pressure signal in the medial–lateral directions) collected for more than 30 seconds and medial–lateral symmetry in force distribution when sat astride a saddle for 10 seconds. Riders were divided into 2 groups either receiving PI to the pelvic region or no intervention. After intervention, the PI group showed a significant reduction in RMS, and initial asymmetry in distribution of pressure was reduced.Preliminary findings suggest that improvements in rider asymmetry and stability can be attenuated through manipulation of the pelvic region. Further work to ascertain the benefits that targeted physiotherapy and training regimes can have on effective horse–rider communication, performance, and behavioral, anatomical, and physiological indicators of welfare in both horse and rider are justified.
... Assessing an animal's use of its thoracic appendages (i.e., its paw, hand, or hoof) is a proven means of establishing motor laterality, which reflects asymmetries in the brain, referred to as lateralization (Tan, 1987;Wells, 2003;Quaranta et al., 2004;Branson and Rogers, 2005;Quaranta et al., 2006). The fundamental importance of balance is recognized in preparing horses for various sports (Murphy and Arkins, 2008). Motor lateralization in horses should be of particular interest to veterinarians and equitation scientists because it may influence musculoskeletal health (McGreevy and Thomson, 2006) and balance during ridden work (McGreevy and Rogers, 2005). ...
Article
The current study used pedometers (designed for the study of human exercise) to record the activity of both forelegs of domestic horses (N = 6) maintained in small groups at pasture. Readings were taken over an 8-hour period daily for 5 days. Over the 5 days, 2 horses were shown to make significantly more movements with the left leg than the right (P = 0.018 and 0.034, respectively). The same 2 horses showed a significant left leg preference every day of the study. For the other horses, less consistent preferences were found. The use of pedometers has potential for scoring motor laterality in large numbers of horses and may overcome the logistical challenges of direct observation. Avoidance of single-day anomalies can be achieved by recording data over several days.
... Sex was taken into account in all analyses because sex differences have been found in laterality in domestic horses (Murphy et al. 2005;Murphy & Arkins 2008) and other species (e.g. rats, Rattus norvegicus: Camp et al. 1984;dogs, Canis familiaris: Wells 2003;Quaranta et al. 2004). ...
Article
Observational field studies were conducted on two remote populations of feral horses in Australia in order to determine whether or not lateralization is a characteristic of Equus caballus as a species or results from handling by humans. Group 1 (N=20) had been feral for 2-5 generations and Group 2 (N=54) had been feral for 10-20 generations. In both groups, left-side biases were present during agonistic interactions (55% threat, 63% attack). Also found were left-side biases in reactivity (67%) and vigilance (54%). Therefore, as in other vertebrates, the right hemisphere appears to be specialised to control agonistic behaviour and responses to potential threats. The leftwards bias was stronger in measures of behaviour involving higher aggression and reactivity. Preferences to place one forelimb in front of the other during grazing were also determined. No population bias of forelimb preference was found, suggesting that limb preferences present in domestic horses may be entrained. Since stronger individual limb preferences were found in immature (N=26) than in adult feral horses (N=45), limb preference may be modified by maturation or experience in the natural habitat. Stronger limb preference was associated significantly with elevated attention to the environment but only in younger feral horses. No sex differences (39 males versus 35 females) in lateralization were found. The findings are evidence that horses show visual lateralization, as in other vertebrates, not dependent on handling by humans. Limb preference, by contrast, does appear to depend on experience.
... Very few animal studies have compared hair whorls with other laterality measures such as motor lateralization . Murphy and Arkins (2004Arkins ( , 2005Arkins ( , 2008) investigated the relationship between cephalic hair whorls and motor laterality in the horse. The authors reported that foals with C whorls presented their right foreleg initially at birth (Murphy and Arkins, 2005); and, that, left-lateralized horses exhibited significantly more CC whorls, whereas right-lateralized horses had more C whorls than expected by chance ( Arkins, 2004, 2008). ...
Article
Several studies have assessed different components of lateralization. However, to date, the relationships between the 3 measures of laterality, structural, motor, and sensory, have not widely been assessed. Specifically, the relationships between structural (hair whorl characteristics) and motor or sensory lateralization have largely been overlooked. Therefore, this study investigated the associations between these measures of lateralization in dogs (n = 114), using hair whorl characteristics (structural), the Kong and First-stepping Tests (motor), and the Sensory Jump Test (sensory). Several associations emerged, revealing the first evidence of a relationship between structural asymmetry (both the presence and direction of a hair whorl in various regions of the body) and sensory lateralization. Specifically, the presence of a whorl on the dog’s left side of the head (cephalic) and thorax was associated with a right visual bias. In addition, right visual bias was probable if the ventral mandibular whorl was present in a counter-clockwise direction (P = 0.008). Our data also demonstrated an association between structural and motor laterality (paw preference). Most notably, dogs with clockwise chest whorls were significantly more right-preferent in the First-stepping Test than those with counter-clockwise whorls (P = 0.010). In addition, an association between measures of motor and sensory lateralization also emerged, representing some of the first evidences of such a relationship in nonhuman animals.
Article
Full-text available
The defining characteristic of laterality is the dominance of one side of the brain controlling specific functions of paired organs or on one side of the body. Structural and functional asymmetries are ubiquitous in horses and range from anatomical features (e.g., the length of long bones) to the gathering of sensory information (e.g., which eye is used to observe unfamiliar scenes) and motor functions (e.g., left–right differences in locomotion). There is a common tendency to assign observed structural or functional asymmetries to lateralization, which often involves more than a simple left–right difference in observed behavior. This narrative review explores the concept of laterality relative to the structural and functional asymmetries reported in horses. Inconsistent and poorly defined terminology, a widely disparate methodology, and a lack of standardized thresholds make it difficult to assess the presence or degree of laterality. Within this context, there seems to be limited evidence of laterality in horses and much more prevalent and stronger support for structural and functional asymmetries due to a wide range of well-established behavioral, nociceptive, and biomechanical mechanisms. The authors caution against generalizing the idea that all observed structural or functional asymmetries in horses are due to laterality.
Article
Full-text available
We examined the relationship between inherited motor-related conformation and orientation of facial hair whorls in Japanese Kiso horses. Eleven horses were divided into clockwise, counterclockwise, and radial groups according to facial hair whorls. We placed six markers on anatomical landmarks of each lateral side in a horse and measured the height of the landmarks, the distance between adjacent landmarks, and the angle of the adjacent landmarks. In the counterclockwise group, the horses tended to exhibit higher values on the left side than on the right side, and the comparison of the height of landmarks revealed a significant difference between both sides. Therefore, the orientation of facial hair whorls may suggest the tendency of motor-related conformation, at least in counterclockwise group.
Article
Full-text available
We tested 35 Lipizzan horses older than 5 years, ridden and healthy in three behavioural tests (handling, fear-reaction, and target training test). Physiological (heart rate and heart rate variability) and anatomical measurements (120 head and body distances and angles) were collected to validate parameters that reliably inform on handling/cooperation, fear/exploration and trainability in horses. Utilizing a standard clustering methodology on the behavioural data, we identified four general types of responses and categorised an individual as intermediate, low fearful, horses with low cooperation or low trainability. We additionally analysed the head morphology following Tellington-Jones and Taylor recommendations and correlated the measurements with data from a horse personality questionnaire. Although allocation to a particular personality group was not associated with these two methods, these groups differed in six anatomical characteristics of head and body. Regardless of the group, our results indicated that shorter horses (<75.9 cm) with a wider muzzle (>10.5 cm) are trustworthy, less fearful and easier to handle and train. We also demonstrated that horses with stronger legs and a wider base of the head have a lower heart rate when exposed to the second trial of the handling test.
Chapter
Since the late 1990s, there has been a substantial increase in horse behavior genetics research. This chapter reviews recent work in molecular genetics, pre- and postnatal effects on behavior, the relationship between hair whorls and temperament, and lateralization in the nervous system. These factors are critical to understanding individual differences. Advancements in molecular genetics have identified genes associated with novelty seeking and gaited horse traits. Foal “imprint” training procedures are reviewed, and a gentle method for training foals is presented. Finding appropriate methods for reducing fearfulness in horses has important practical implications. High hair whorls are associated with reactivity, but differences are less apparent in calm breeds. Behavioral asymmetry is a fundamental feature of animal brains. Left-eye systems control avoidance behavior and right-eye systems control approach behaviors. An understanding of the cognitive and perceptual abilities is necessary to ensure horses receive proper training, handling, management, and care.
Article
Full-text available
Objective: According to oral traditions of horse caretakers and trainers, the differences in the position and number of facial hair whorls may be associated with temperamental traits. Elucidating genetic background of facial hair whorls and its relationship to temperamental traits may promote more efficient breeding and maintenance of racehorses. In this study, we estimated heritabilities of the position and number of facial hair whorls in Japanese Thoroughbred horses. Results: The number of facial hair whorls varied from one to four and heritability estimate in 4024 Thoroughbred horses was low (h2= 0.160). The positions of facial hair whorls were categorized into high, medium, and low, based on their locations. This trait was estimated to have high heritability (h2= 0.643) in 3782 Thoroughbred horses. These results indicated that a larger proportion of the variation in the studied population was due to genetic factors for facial hair whorls position. Because a similar result was also observed in another horse breed, Polish Konik horses, high heritability of facial hair whorl position may be characteristic of multiple horse breeds. We expect that these results will stimulate future studies to elucidate the relationship among temperamental traits and facial hair whorls in all horse breeds.
Chapter
Success in working with livestock is not related to the intelligence or lack of it on the part of the animals. The process of getting an animal from point A to point B can be a distressful, reactive, trial and error attempt in which the human finally lucks out at getting the job done, or it can be a stress-free experience for the human and the animals. Which type of experience it is will depend on the human's understanding of how an animal perceives its world, how animals learn, the relative importance of its social peers, and what motivates it to move. With that knowledge, appropriate techniques can be used to humanely create an outcome that is both effective and efficient.
Article
This pilot study tested for an association between facial hair whorl characteristics and behavioral responses to a fearful stimulus in horses. Nineteen riding horses were categorized based on hair whorl characteristics (height, lateral location, and rotation). Each horse was subjected to a novel object test where an umbrella was suddenly opened. The turning response was recorded. Hair whorl rotation showed a correlation with turning response with P=0.04. Clockwise hair whorls were associated with turning to the right, and counterclockwise hair whorls with turning to the left. There were no significant correlations between hair whorl lateral location or height and direction turned (P>0.05). In conclusion, facial hair whorls may be used as a non-invasive method to predict turning response in horses.
Chapter
Since the late 1990s there has been a substantial increase in horse behavior genetics research. This chapter reviews recent work in molecular genetics, pre-and postnatal effects on behavior, the relationship between hair whorls and temperament, and lateralization in the nervous system. These factors are critical to understanding individual differences. Advancements in molecular genetics have identified genes associated with novelty seeking and gaited horse traits. Foal "imprint" training procedures are reviewed, and a gentle method for training foals is presented. Finding appropriate methods for reducing fearfulness in horses has important practical implications. High hair whorls are associated with reactivity, but differences are less apparent in calm breeds. Behavioral asymmetry is a fundamental feature of animal brains. Left-eye systems control avoidance behavior and right-eye systems control approach behaviors. An understanding of the cognitive and perceptual abilities is necessary to ensure horses receive proper training, handling, management, and care.
Article
Full-text available
Laterality can be defined as an individual's cerebral hemisphere or motor handed-ness/pawed-ness/hoofed-ness preference, which is recognized in multiple animal species. It has been proposed that the concept can be used to evaluate and predict animal behavioural responses or to determine performance-related variables. This article examines research related to laterality predominately in the horse and its application in clinical practice, in relation to injury prevalence, training and rehabilitation. It concludes that the recognition of hemisphere lateral preference can be used to determine a horse's reactions in novel environments and could inform both clinical and training practice. In addition, assessment of motor lateral preference would be a beneficial addition to integrate into equine training programmes to optimize performance and should be considered when determining rehabilitation programmes post injury.
Article
Use of the right hand by humans for speech-related hand gestures, writing and throwing exemplifies motoric asymmetry. There are reports of asymmetry in many other animal species, including reports of left preference in emotional responsivity, spontaneous behaviour and the trained performance of the horse, Equus ferus caballus. The present study used the novel approach of using judges' scores to examine asymmetry in an equestrian event. The study analysed the scores of five judges evaluating the reining performance of 482, three-year-old American Quarter Horses competing in a major competition. Reining requires that the horses perform the manoeuvres of spin, circle and stop directed to either the left or right and symmetrical performance is featured in the judging criteria. The scores were sensitive to performance level, sex and manoeuvre, but there was no evidence of a population asymmetry in the left vs. right direction of the manoeuvres. The results are discussed in relation to need of using a large number of subjects in measuring asymmetry, the expression of individual vs. population asymmetry as a function of morphological and behavioural measures, and the influence of behavioural training on asymmetry.
Article
Background: Relationships have been established between trichoglyphs (whorls) and temperament, laterality and the occurrence of abnormal behaviour in multiple species. Within the equine industry stereotypic behaviour is considered to impair performance and reduce value in affected individuals, potentially reducing career longevity and compromising welfare through preventing their expression when they occur. Aim: The study aimed to determine whether dermatoglyph profiles (whorl morphology, orientation, number and topography) could be used to predict susceptibility to perform abnormal repetitive behaviours (ARB) in thoroughbred racehorses. Method: Trainer interviews combined with experimenter direct observation were used to ascertain expression of ARBs. Whorls were digitally photographed and overall whorl profiles derived using remote computer analysis. Results: Non-parametric statistical analysis revealed significant relationships between aspects of whorl morphology and performance of ARBs (round epicentre: sum ARBs p<0.05; round gross morphology: sum ARBs p<0.0001), orientation and distribution (abdominal trichoglyph orientation asymmetry: sum ARBs p<0.05; clockwise orientation: sum ARBs p<0.05 and social stereotypies p<0.05). Conclusion: This study indicates that whorls may be viable physical indicators of predisposition to perform ARBs in the thoroughbred. Assessment of dermatoglyph profiles have potential to assist with the improvement of horse welfare via informed management practices if patterns exposed are transferable to other breeds and can reliably predict individuals with a propensity to develop ARBs.
Article
Full-text available
Horses are one-sided, not only on a motor level, but they also prefer to use one eye, ear or nostril over the other under particular circumstances. Horses usually prefer using the left eye to observe novel objects and humans. This preference is more marked in emotional situations and when confronted with unknown persons. Thus the horse’s visual laterality provides a good option for assessing its mental state during training or in human-horse interactions. A strong preference for the left eye may signal that a horse cannot deal with certain training situations or is emotionally affected by a particular person.
Article
A Y-maze preference test was used to investigate whether horses prefer a shorter riding treatment over a longer riding treatment. In a pilot study (n = 4 horses), the maze was positioned with the 2 arms each pointing toward one of the short sides of the indoor arena, and in the main study (n = 14), the maze was rotated by 90°. Horses were 11 ± 4.4 years old and ridden regularly for at least 5 times/wk. They were conditioned to associate 1 exit of the maze with 1 lap of riding (R1), covering a distance of approximately 40 m at the walk or trot according to a predetermined schedule, and the other exit with 2 such laps (R2). Immediately afterward, riders dismounted, horses were led into the maze, and horses were let loose to make their choice in the maze. After exiting the maze, the rider mounted again and rode according to the chosen treatment. This procedure was repeated on the same day until statistical significance (P < 0.05) of preference was reached or up to a maximum of 35 trials. In addition, behavioral observations and heart rates were recorded. In the pilot study, all horses, regardless of the associated treatment, chose the left arm, which, unfortunately, pointed toward the arena's exit door. If horses were not caught immediately after exiting the maze (n = 5 occasions), they walked or trotted straight to the door. In the main study, 4 horses significantly preferred R1, 2 horses significantly preferred R2, and 8 horses had no significant preference. Heart rates were significantly (P < 0.05) higher during R2 (87.4 ± 2.6 bpm) than during R1 (79.5 ± 2.4 bpm). Except for tail swishing, no significant differences were found for the frequency of occurrence of behavior patterns between R1 and R2. Over the course of repeated trials, some horses became increasingly reluctant to enter and walk through the maze, and most showed increasing resistance to being remounted (e.g., sidestepping). Overall, the experimental setup did not seem to be appropriate to answer the research question. It is likely that the repeated mounting and dismounting caused discomfort or confused many of the horses to an extent that they did not actively select a treatment but rather searched for ways to evade further mounting (and riding). In conclusion, horses did not show a clear preference for either shorter or longer riding bouts, but their behavioral reactions indicate that they perceived mounting as uncomfortable and that their motivation to rejoin their herd-mates and/or to obtain feed in the barn was greater than their motivation to being ridden at all. Nevertheless, pronounced individual differences also seem to exist, with some horses showing little aversion to, and perhaps enjoyment of, being ridden, whereas others clearly preferring not to be ridden.
Article
According to the principles of negative reinforcement, when an aid has been given to an animal, it should be released as soon as the desired response has been achieved, and, if performed well, may be associated with fewer conflict behaviors than otherwise. In riding, pressure in the horse’s mouth from the bit is used to give signals to the horse, and both rein tension and patterns of releasing this tension will vary. The aim of this pilot study was to study horse behavior during 2 different methodologies used to shape relatively naïve horses to a deceleration signal while making downward transitions from trot to walk. Method 1 involved relief from rein tension at the first attempt to perform a correct response (M1), and method 2 entailed that rein tension was relieved at the completed correct response (M2). Four horses were ridden by 4 riders over 4 days (1 rider each day), and each horse made 10 transitions each day for each method, which produced 320 transitions. Rein tension was recorded, and horse behavior and rider signal behaviors were evaluated from video recordings. Horse behavior was divided into the following 3 different categories: “pushing against the bit,” “moving away from the bit,” and “decelerating.” Linear models were constructed tracking the percent of the transition time that horses demonstrated at least 1 behavior in the “pushing against the bit,” “moving away from the bit,” and “decelerating” categories, and with random effects for rider, horse, and transition number nested within horse. Fixed effects analyzed were the methods, proportion of the transition time above 30 N for each rein, and the rider signal behaviors. M1 and M2 had on average 19% (standard deviation: 16) and 38% (standard deviation: 23) of the time with >30 N per rein, respectively. In the models for the “pushing against the bit” behaviors, M2 increased rein tension and “exerting pressure on the reins” increased the level of these behaviors. “Releasing pressure” interacted with “pulling back on the reins”; this combination was associated with an increased level of “pushing against the bit” behaviors. The “decelerating” behavior was associated with lower rein tension. In the “decelerating” behavior models, “pulling back on the reins” led to decreased “decelerating” behavior, whereas “still hand” and “releasing pressure” led to increased “decelerating” behavior; however, the interaction “pulling back on the reins” and “releasing pressure” led to decreased “decelerating” behavior. “Moving away from the bit” had no significant determinants. We concluded that fewer “pushing against the bit” behaviors were created by M1 and that a lower rein tension was associated with the “decelerating” behavior. Reinforcing the horse’s attempts, to assist in finding the correct response, benefits the welfare of the horse, and importance of a light hand should be continuously emphasized during riding education.
Article
The degree of lateralization (LI) indicates both the direction and strength of a paw preference. Here, a positive value is indicative of a right paw bias, and a negative value of a left paw bias. Higher numbers on the positive side of the scale and lower numbers on the negative side of the scale indicate a greater strength of that lateralization. The strength of motor lateralization (|LI|) is the absolute value of the LI. The use of absolute value removes directionality (i.e., does not indicate left or right paw bias) and instead indicates only the strength of the paw preference. Both LI and |LI| have been associated with behavioral differences in a range of species. The assessment of motor lateralization in the dog can be conducted by observing the paw used to perform motor tasks.
Article
The aim of this study was to determine whether objective measures of laterality could be used to identify dogs with a high probability of successfully completing a Guide Dog Training Programme. Three categories of laterality (motor, sensory, and structural), were assessed in 114 dogs entering guide dog training. Significant predictors of success were identified: the direction of laterality (P=0.028), paw preference category in the 'Kong' test (P=0.043), hindpaw clearance height (P=0.002), laterality indices for a number of measures in the Sensory Jump test, and chest hair whorl direction (P=0.050). This is the first study to report a structural marker of canine behaviour. All three categories of laterality may be used to predict the suitability of dogs for guiding work, and by identifying predictors of success, resources can be more efficiently utilised on dogs with greater potential.
Article
Monocytes/macrophages are critical for both immunity and homoeostasis. They are the outposts of the immune system in detecting invading pathogens or foreign antigens for homoeostatic clearance and antigen processing for the initiation and effector stages of both innate and adaptive immunity. In addition, monocytes/macrophages often function as control switches for immune system balance between pro- and anti-inflammatory reactions. In the beginning of this article, I would like to briefly introduce the achievements of Metchnikoff and Ehrlich in immunology, including Metchnikoff's cell theory, since they have both greatly influenced the advancement of modern immunology. Additionally, I will honour the 100th anniversary of the 1908 Nobel Prize in Physiology or Medicine. Next, I would like to emphasize the concept of the MPS (mononuclear phagocyte system) by examining recent developments regarding the MPS. Thus the article consists of three parts. The first part describes the regulation of growth and differentiation in the MPS. The second part addresses how the key macrophage transcription factor gene PU.1 and the csf1r (colony-stimulating factor-1 receptor gene) play a critical role in haematopoietic myelopoiesis, or the generation of the cells of the MPS. The third part describes PMA-induced monocyte/macrophage differentiation and immune modulation of suppressor macrophages. Finally, this review discusses the latest findings and implications regarding the MPS and macrophages.
Article
Full-text available
Most horses have a side on which they are easier to handle and a direction they favour when working on a circle, and recent studies have suggested a correlation between emotion and visual laterality when horses observe inanimate objects. As such lateralisation could provide important clues regarding the horse's cognitive processes, we investigated whether horses also show laterality in association with people. We gave horses the choice of entering a chute to left or right, with and without the passive, non-interactive presence of a person unknown to them. The left eye was preferred for scanning under both conditions, but significantly more so when a person was present. Traditionally, riders handle horses only from the left, so we repeated the experiment with horses specifically trained on both sides. Again, there was a consistent preference for left eye scanning in the presence of a person, whether known to the horses or not. We also examined horses interacting with a person, using both traditionally and bilaterally trained horses. Both groups showed left eye preference for viewing the person, regardless of training and test procedure. For those horses tested under both passive and interactive conditions, the left eye was preferred significantly more during interaction. We suggest that most horses prefer to use their left eye for assessment and evaluation, and that there is an emotional aspect to the choice which may be positive or negative, depending on the circumstances. We believe these results have important practical implications and that emotional laterality should be taken into account in training methods.
Article
Full-text available
The relationship between facial hair whorl position and reactivity, as assessed by behavioural measures (handling score=HS; startle reaction to a suddenly appearing novel object=SR; latency to touch a novel object=LNO) and heart rate measures (mean HR; increase in heart rate=IHR) were studied using 55 Konik horses reared either under conventional stable conditions or in the forest reserve. Horses were classified into four groups according to the whorl position and/or shape: (1) high, single whorl above the top eye line, n=9; (2) medium, single whorl between the top and the bottom eye line, n=30; (3) low, single whorl below the bottom eye line, n=10; and (4) elongated or double whorl, n=6. Horses with a high whorl position demonstrated a lesser degree of manageability as expressed by a lower HS compared to individuals with medium (P=0.002) or low whorl positions (P=0.016). Horses with different whorl positions did not differ significantly in their startle response to a suddenly appearing novel object (P=0.685). The horses with an elongated or double whorl, which appeared only in the forest group, took significantly longer to approach the novel object than horses with medium (P=0.006) or low (P=0.005) whorl positions. No significant differences in mean HR and IHR between groups (HR: P=0.629 and IHR: P=0.214) were found. In conclusion, this study supports the relationship between the position of the hair whorl on the horses’ head and their manageability during handling, as well as the latency to approach an unknown object.
Article
Full-text available
A survey of more than 5000 years of art work, encompassing 1180 scorable instances of unimanual tool or weapon usage, revealed no systematic trends in hand usage. The right hand was used in an average of 93 percent of the cases, regardless of which historical era or geographic region was assessed.
Article
Full-text available
Paw preference assessed by a food-reaching test was studied in male and female cats. Of the total sample (N = 66), 34 (51.5%) were right-preferent, 24 (36.4%) left-preferent, and 8 (12.1%) ambilateral. In the total sample, there was evidence for an overall paw preference, general paw preference, right-, and left-paw preference. The distribution of the right- minus left-paw reaches was neither normal, nor U or J shaped. Of the males (N = 24), 10 (41.7%) were right-pawed, 12 (50.5%) left-pawed, and 2 (8.3%) ambilateral. In males, there was evidence for an overall, general, and right-, left-paw preference relative to no preference. The right- minus left-paw reaches fitted to guassian data with two prominent peaks due to the right- and left-preferents. In females (N = 42), 22 (52.4%) were right-preferent, 14 (33.3%) left-preferent, and 6 (14.3%) ambilateral. There was an overall, general, and right-preference but not a left-preference relative to no preference. The distribution of the right- minus left-paw reaches was neither normal nor U or J shaped. The female right-preferents showed a right-bias compared to males. The left-preferent males were more left-preferent than the right-preferent males are right preferent. The mean right- minus left- paw reaches for the female right-preferents were significantly higher than those for the male right-preferents. There was no significant difference between the right- minus left-paw reaches of the male and female left-preferents. The paw preferences exhibited consistency over time; no learning tendencies were established during testing periods for at least 10 days. Considering the mean right-paw reaches for each successive day (N = 10), the mean right-paw uses in the right-preferents was higher in females than males. The mean left-paw uses in left-preferents was about the same for males and females. In males, the mean left-paw uses for the left-pawed males were higher than the right-paw reaches for the male right-preferents. In females, there was no difference between the right paw reaches of the right-preferents and the left-paw reaches of the left-preferents. It was concluded that there is a right-bias in paw preference of cats, which is caused by the female right-preferents under the influence of a biological factor.(ABSTRACT TRUNCATED AT 400 WORDS)
Article
Full-text available
A population of 194 lemurs (Lemur spp.), 116 males and 78 females, from 1 to 30 years of age, was assessed for lateralized hand use in simple food reaching with a minimum of 100 reaches per animal. A hand preference was present in 80% of the population with a bias for use of the left hand that was most characteristic of male lemurs and young lemurs. The results confirm the presence of lateralization in prosimians, and we interpret the sex and age differences in relation to current theories of neural lateralization.
Article
Full-text available
The distribution of paw preferences were studied in 28 dogs. The paw preference was assessed by counting the right and left paw movements performed to remove an adhesive plaster from the eyes. The significance of the right minus left paw reaches in percentages was evaluated statistically in each animal. There were three distinct groups in respect to paw preferences in dogs: right-preferent (57.1%), left-preferent (17.9%), and ambidextrous (25.0%). Statistical analysis showed that the observed frequencies for each group were not merely chance variations which would be expected in a random sample. It was concluded that the population bias can be expressed in a distribution skewed toward a right-hand bias as seen in man.
Article
Full-text available
The objective of the study was to examine the career profile of the average racehorse in order to establish normal values for performance. Records of race performance for a population of 762 horses randomly-selected from the 1972 registrations of the Canadian Standardbred Horse Society were summarized to provide annual statistics for number of races, money won, and times for the mile (race times) over the period 1974 to 1983 inclusive. Results were analyzed to determine the influence of sex, gait, age, and year of the first race. The transformation log (1 + X) was used to achieve normality where necessary. The 95% confidence interval for the mean (mean range) for career total for number of races was 21.8 to 69.6. Of the horses which raced, 30% raced 20 or fewer times, 29% raced more than 100 times. Females raced significantly less often than either males or geldings (p less than 0.001), pacers significantly more often than trotters (p less than 0.01). Regardless of the age at which they first competed all horses were raced lightly in their first race year. Mean range for career total for money won was 2,212to2,212 to 2,798 (n = 507). Of 507 horses which raced, 65.8% earned less than 10,000,6.310,000, 6.3% more than 50,000. Trotting geldings had the highest mean money won, mean range 2,448to2,448 to 38,105. Mean range for money won per race for all horses racing was 67.77to67.77 to 74.51. Overall, 58% of horses earned less than 100perrace,4.5100 per race, 4.5% over 500. Only 4.5% of horses racing met their immediate training expenses. Increase in age at first race was associated with highly significant and progressive reductions in career races, money won, and money won per race. Of 507 horses which raced, 409 or 80% won at least one race and thus acquired an official winning time or mark. Population mean for career mark was 2.126 min (2.07.3.). Population trend in mean mark was for progressive improvement over the ten year racing period amounting to 0.0968 min or 5.81 s. The average horse achieved its best winning time 2.55 years after starting racing, at a mean age of 5.27 years. The results suggest that the best nonwinning time may be a better indicator of potential than the best winning time. For the average as opposed to the superlative horse, number of races appears to be of greater importance than speed.(ABSTRACT TRUNCATED AT 400 WORDS)
Article
Full-text available
Laterality in paw use was investigated over a period of 6 years in 44 domestic cats trained to perform a reaching movement toward a moving spot of light. Both paw preference and paw performance were recorded. At a 50 percent criterion, no significant paw preference was found at the level of the group. When a 90 percent criterion was considered, 23 subjects had a significant preference for one paw. Among these strongly lateralized animals, there were more left- (N = 17) than right-pawed (N = 6) cats. The analysis of visuo-motor performances included reaction time, movement time, and reaching accuracy. Lateralized cats had a faster reaction time than nonlateralized cats. The more-used paw had a shorter reaction time, a shorter movement time, and was also more accurate than the less-used paw. Thus, the findings demonstrate a functional advantage of being lateralized. Moreover, the results confirm the existence of an asymmetry of paw preference in cats and show a consistent relation between paw preference and performance.
Article
Full-text available
Twin family data can cast light on the longstanding problem about the influences of genes and environment on the etiology of left-handedness. Therefore, hand preference was assessed in 1700 adolescent twin pairs and their parents. Left-handedness (LH) appeared not significantly enhanced among twins compared to the general population. In addition the following observations were made: (1) Significant more LH in first born twins than in second born twins. (2) Significant higher left-handedness association in MZmm pairs compared to DZmm pairs and not or may be marginally so in MZff versus DZff pairs. These results, combined with the observations that (a) left-handed fathers increase the probability of LH in sons but not in daughters; (b) LH in mothers increases LH prevalence in both sons and daughters to the same degree; and (c) very low birth weight, corrected for the effect of gestational age, increases LH prevalence in first born twins only, make an environmental explanation more likely. The possibility that exposure to prenatal male hormones - to which low birth weight and high birth stress children are more vulnerable - might be a crucial condition for the etiology of LH, is discussed.
Article
Full-text available
This study examined intertask consistency in handedness across multiple measures of hand use in a sample of 187 chimpanzees (Pan troglodytes). Hand preferences for 2 to 6 measures were collected from the sample, and hand preference scores were derived on the basis of the individual hand preferences for each measure. Seven of 15 possible intratask correlations were significant, with some degree of clustering depending on the motor demands of the tasks. Two overall measures of handedness revealed population-level right-handedness in the chimpanzees, although the degree of bias was reduced for chimpanzees tested on more than 3 measures of hand use. The results are interpreted in the context of several recent studies that proposed theoretical models of handedness in nonhuman primates.
Article
Full-text available
Right handedness is one of the most prominent markers of human functional brain asymmetry. Deviation from this norm appears to be associated with certain developmental disorders. While many studies have dealt with the genetic contribution to the determination of handedness, few have examined whether environmental factors that are subtler than forced hand switching can modulate the development of handedness. In this study, we exposed rats to a novel environment for 3 min daily during their first 3 weeks of life and found that their paw preferences during both infancy and adulthood showed a leftward shift compared with the controls. This result suggests that 'handedness' can be modified by rather subtle early environmental manipulation. Since exposure to a novel environment does not involve a direct asymmetric activation of the sensory--motor system underlying paw-use, mechanisms beyond this paw-specific system must exist to mediate the observed modulation of 'handedness'.
Article
Full-text available
Theories concerning the cause of right- or left-hand preference in humans vary from purely learned behavior, to solely genetics, to a combination of the two mechanisms. The cause of handedness and its relation to the biologically specified scalp hair-whorl rotation is determined here. The general public, consisting of mostly right-handers (RH), shows counterclockwise whorl rotation infrequently in 8.4% of individuals. Interestingly, non-right-handers (NRH, i.e., left-handers and ambidextrous) display a random mixture of clockwise and counterclockwise swirling patterns. Confirming this finding, in another independent sample of individuals chosen because of their counterclockwise rotation, one-half of them are NRH. These findings of coupling in RH and uncoupling in NRH unequivocally establish that these traits develop from a common genetic mechanism. Another result concerning handedness of the progeny of discordant monozygotic twins suggests that lefties are one gene apart from righties. Together, these results suggest (1) that a single gene controls handedness, whorl orientation, and twin concordance and discordance and (2) that neuronal and visceral (internal organs) forms of bilateral asymmetry are coded by separate sets of genetic pathways. The sociological impact of the study is discussed.
Article
Full-text available
We have established that lateral biases are characteristic of visual behaviour in 65 horses. Two breeds, Trotters and French Saddlebreds aged 2 to 3, were tested on a novel object test. The main finding was a significant correlation between emotionality index and the eye preferred to view the novel stimulus: the higher the emotionality, the more likely that the horse looked with its left eye. The less emotive French Saddlebreds, however, tended to glance at the object using the right eye, a tendency that was not found in the Trotters, although the emotive index was the same for both breeds. The youngest French Saddlebreds did not show this trend. These results are discussed in relation to the different training practices for the breeds and broader findings on lateralisation in different species.
Article
Hair whorl position on the forehead may be of value in selecting breeding cattle for a calm temperament. A total of 1500 cattle weighing 180–360 kg were temperament rated on a four-point scale. Seventy-two percent of the cattle were European × British breed crosses and 28% were Zebu × dairy breed crosses from Mexico. Cattle with a round hair whorl located above the eyes became significantly more agitated while they were restrained in a squeeze chute (crush) compared to cattle with a hair whorl located either between the eyes or below the eyes. For both the Bos taurus and Bos indicus crossbreeds, animals with hair whorls located below the eyes were rated calmer. There is a positive linear relationship (P < 0.001) between cattle temperament while restrained in a squeeze chute and the location of facial hair whorls. The cattle observed in this study were extensively raised and had a large flight zone when approached by people. Casual observations indicate that the relationship between hair whorl position and temperament is most easily observed in cattle that do not have daily close contact with people.
Article
We investigated lateralisation in horses because it is likely to be important in training and athletic performance. Thoroughbred horses (n=106) were observed every 60s for 2h, when they were at pasture, and the position of the forelimbs in relation to one another was recorded. There was a population bias skewed to standing with the left forelimb advanced over the right (i.e. directional lateralisation). Using the first 50 observations, the distribution of preferences was 43 significantly left, 10 significantly right with 53 being non-significant (i.e. ambidextextrous). The strength of motor bias increased with age, suggesting maturation or an influence of training.The horses were also presented with an olfactory stimulus (stallion faeces) to score the tendency to use one nostril rather than the other. A significant preference to use the right nostril first was shown in horses under 4 years of age (n=61) but not in older horses. Of the 157 horses tested for nostril bias, 76 had been assessed for motor bias and so were used for analysis of the relationship between laterality in the two modalities. There was no significant relationship between direction of foreleg motor bias and first nostril used, total number of inhalations or laterality index of nostril use.The absence of a correlation between laterality of nostril use and motor bias indicates that lateralisation of the equine brain occurs on at least two levels of neural organisation—sensory and motor—a finding that is consistent with other examples of lateralisation in species that have been examined in more detail.
Article
Idiosyncratic motor behaviour was investigated during four experimental procedures in 40 horses (males=20, females=20) to establish if horses revealed evidence of significant right or left laterality. The experimental procedures included (1) detection of the preferred foreleg to initiate movement (walk or trot), (2) obstacle avoidance within a passageway (right or left), (3) obstacle avoidance when ridden and (4) idiosyncratic motor bias when rolling. The influence of the horses’ sex on both the direction and the degree of the laterality was explored within and between experimental procedures. The findings showed that the direction, but not the degree of idiosyncratic motor preference in the horses was strongly sex-related. Male horses exhibited significantly more (t=3.74, d.f.=79, P
Article
This study examined the relationship between motor laterality in horses bred for different types of work and therefore different temperaments. Foreleg preference during grazing was measured in three populations of domestic horse, Thoroughbreds (TB, bred to race at the gallop), Standardbreds (SB, bred for pacing) and Quarter Horses (QH, in this case bred for so-called “cutting work” which involves manoeuvring individual cattle in and out of herds).With a one-sample t-test, TBs showed strong evidence of a left preference in motor laterality (P=0.000), as did SBs (P=0.002) but there was no convincing evidence for laterality in QH (P=0.117). However, the increasing trend in left preference from QH to SBs then TBs was associated with increasing differences between individual horses within a breed. The overall preference (either left or right) increased with age (P=0.008) and the rate of increase varied with breeds. The presence of a higher proportion of left-foreleg preferent individuals in TBs and SBs compared with QH may indicate that their training or selection (or both) has an effect on motor bias.
Article
Five hundred four-year-old Standardbred Trotters in training were examined in a study on the correlation between conformation, soundness and racing performance. In 39 horses marked hindquarter asymmetries were observed when they were standing squarely on all four feet. The asymmetries were seen as obvious height differences between the left and right tubera sacrale. In 30 cases the left tuber sacrale was lower and in nine cases the right tuber sacrale was lower. The horses showing hindquarter asymmetry were of significantly larger body size than the 461 horses not showing the asymmetry. There was no sex difference in the incidence of hindquarter asymmetry. The asymmetric horses had significantly lower total earnings, a lower number of races per horse and less good racing records (min/km) than the remaining 461 horses. The trainers reported that the asymmetric horses often had difficulties in performing at speed. In most horses, the asymmetry had not been observed until the examination. Past clinical records of 11 of the 30 asymmetric horses were available. In only one of the 11 horses had the asymmetry been considered of clinical importance. It was concluded that the described hindquarter asymmetries are important signs indicating that there is an enhanced risk that the affected horses will not become successful Trotters.
Article
Lateralized behaviour has been documented in non-human species, although many observers believe that it occurs at the individual rather than the population level. Its occurrence in humpback whales,Megaptera novaeangliae, in Massachusetts Bay was investigated by examining active behaviour types in which preference could be given to one direction or side. These included head breaching (direction of spin), flippering (right or left) and tail breaching (direction of movement). In addition, persistent abrasions on the right or left jaw resulting from turns to one side during bottom feeding were noted. Of 75 individuals with jaw abrasions, 60 (80%) showed abrasions on only the right jaw, while 15 (20%) had abrasions on only the left. No whales had abrasions on both jaws. Location of abrasions was consistent in all resighted individuals for up to 12 years. Two of the three active behaviour types were not strongly lateralized: directional bias was seen in only five of 21 bouts (23·8%) of breaching, and in three of 11 bouts (27·3%) of tail breaching. However, 22 of 34 bouts (64·7%) of flippering showed a bias towards one direction (generally the right). Furthermore, direction of bias in all behaviour types was individually consistent between bouts and was strongly correlated with abrasions on the corresponding jaw (P=0·0032). The sex ratio of individuals with jaw abrasions, and of those showing directional bias in active behaviour, did not differ significantly from that of the overall population. Overall, these data suggest that humpback whales exhibit some behavioural asymmetries, at least one of which is at the population level. This result suggests assymmetry of function in motor or somatosensory representations, although too little is known about the brain of this species to permit definitive conclusions.
Article
There is evidence of superior visuo-spatial ability in males compared to females in most species investigated to-date. However, no known studies have addressed this issue in the equine. Equine visuo-spatial ability was investigated using a novel test apparatus with a sample of 62 horses (males=34 and females=28) during a series of six tests, where the horses were required to access a food source. The test apparatus consisted of a series of four adjacent stalls, each of which had a feed bin and a moveable barrier. The test apparatus was designed such that the breastplate barriers controlled and limited access by the horses to feed bins in all but one stall during each test. Male horses performed such that there were significant differences (P<0.05) in the ability of the subjects to complete all six tests in a mean time of 30 s or less per test. There were significant differences in mean completion times for male subjects between test 1 and test 2 (P<0.05), test 1 and test 3 (P<0.001), test 1 and test 4 (P<0.05) and test 1 and test 5 (P<0.05). There were no significant differences in mean completion times between any of the six tests for female subjects. Males had a lower mean total number of errors during all tests. Male horses also successfully completed significantly more tests than females (P<0.05). These results provide the first behavioural demonstration of superior visuo-spatial ability in male horses, similar to that reported in other species.
Article
Individual behavioural reactions of adult horses in a variety of experimental tests were compared with ratings by riding teachers. The tests were made in a non working situation, with the animals being released in an arena, a box (arena test, new object test, learning tests) or handled (new object/handling situation). The traits rated by teachers were fearfulness, nervousness, gregariousness and learning abilities at work (ridden or handled). Despite a great homogeneity in the reactions exhibited by the horses in the different situations, large individual differences were present. Correlations appeared between the reactivity in the arena test and the score of gregariousness, between the reactivity in the novel object test and the rating of nervousness when ridden, between the results in the handling test and the rating of general fearfulness and between the ability to memorise an instrumental task and the score of general learning ability. Such results strengthen the idea that there are underlying behavioural dispositions that are stable across situations and that the experimental tests may be good predictors of the temperament in untrained animals.
Article
Different tests were used to assess different aspects of the emotionality of 1–3 year-old horses: arena test; a `novel object' test; and a handling test. In reaction to the test situations no important differences were observed according to age or sex in the behaviour patterns, but clear individual differences were observed within these classes. The arena test seemed to reveal the degree of gregariousness of the animals whereas the results in the two other tests were correlated and seemed to reflect an inherent degree of fearfulness in the horse. Indices were developed that enabled to rank the animals, by taking into account all behaviour patterns shown. Such individual characteristics might have some genetic basis: half-siblings tended to behave the same way in most cases.
Article
Scientists and equestrians continually seek to achieve a clearer understanding of equine learning behaviour and its implications for training. Behavioural and learning processes in the horse are likely to influence not only equine athletic success but also the usefulness of the horse as a domesticated species. However given the status and commercial importance of the animal, equine learning behaviour has received only limited investigation. Indeed most experimental studies on equine cognitive function to date have addressed behaviour, learning and conceptualization processes at a moderately basic cognitive level compared to studies in other species. It is however, likely that the horses with the greatest ability to learn and form/understand concepts are those, which are better equipped to succeed in terms of the human-horse relationship and the contemporary training environment. Within equitation generally, interpretation of the behavioural processes and training of the desired responses in the horse are normally attempted using negative reinforcement strategies. On the other hand, experimental designs to actually induce and/or measure equine learning rely almost exclusively on primary positive reinforcement regimes. Employing two such different approaches may complicate interpretation and lead to difficulties in identifying problematic or undesirable behaviours in the horse. The visual system provides the horse with direct access to immediate environmental stimuli that affect behaviour but vision in the horse is of yet not fully investigated or understood. Further investigations of the equine visual system will benefit our understanding of equine perception, cognitive function and the subsequent link with learning and training. More detailed comparative investigations of feral or free-ranging and domestic horses may provide useful evidence of attention, stress and motivational issues affecting behavioural and learning processes in the horse. The challenge for scientists is, as always, to design and commission experiments that will investigate and provide insight into these processes in a manner that withstands scientific scrutiny.
Article
A survey of 1,177,507 U.S. men and women between the ages of 10 and 86 included questions regarding hand preference for writing and throwing. Three effects were observed. Individuals with at least some left motoric bias comprised a smaller percent of the population with advancing age. This finding provides large-scale confirmation of a previously described phenomenon. Among sinistrals, concordance for writing and throwing was 2.2 times as prevalent as left-writing with right-throwing, and 4.1 times as prevalent as right-writing with left-throwing. These sinistral subpopulations displayed distinct and stable prevalence prior to age 50 and changing patterns of prevalence subsequent to age 50. The results confirm a decrease with age in the prevalence of sinistrality, but indicate that age-specific rates of mixed- and left-handedness are distinct. The implications for hypotheses regarding age-related change in the prevalence of sinistrality are discussed.
Article
Information on handedness, assessed as writing-hand, was collected from 197 MZ twin pairs and 203 DZ twin pairs and from their parents, spouses, and children. Associations for pairs of relatives were studied by 2 X 2 tables, computing chi squared-values and tetrachoric correlations. Correlations of about .3 were obtained for mother-offspring and sibling pairs, while for cousins the correlation was .25 (in a small sample). No other significant associations were found, not even for twins. These results suggest only a small, if any, genetic effect, and only a small environmental between family effect, most of which seems to be a maternal effect. The lack of cotwin correlations and correlations for one of the twins with her/his ordinary brothers/sisters suggest the existence of an effect specific to twins, since the correlation for pairs of ordinary siblings is significant. Conclusions drawn from twin studies alone may be biased. The frequency of left-hand writers has increased from 1% to 10% in the different age groups born during the last century in Norway. This age effect is present mainly in hand writing and not so much in handedness generally, suggesting a decrease in cultural repression against left-hand writing.
Article
Ten trotting Standardbred colts were recorded by high-speed cinematography at the ages of eight, 12 and 18 months. The horses were trotting on a treadmill operating at 4.0 m/secs. Five horses were subjected to a programme of intensified training from eight months of age, whereas the others were not trained and acted as controls. The films were analysed on a semi-automatic film-reading equipment and a number of variables used to demonstrate the gait symmetry were calculated and scaled by computer. Certain differences between left and right diagonal and contralateral pair of limbs, respectively, were noted, suggesting that laterality in horses may be inherited. The most pronounced systematic differences were found in 18-month old horses in the trained group. The results show the importance of careful gait examination and comprehensive coordination training at an early age.
Article
Bilateral asymmetry in gallop stride limb contact patterns of four Quarter Horse fillies was documented by high-speed cinematography. Horses were filmed with rider by two cameras simultaneously while galloping along a straightaway. Even though signaled for each gallop lead an equivalent number of times, horses frequently switched leads, selecting the left lead nearly twice as often as the right. Velocities and stride lengths were greater for the left lead than the right, but stride frequencies did not differ between leads. Velocity effects were partitioned out in limb contact data analysis to enable the determination of persistent gallop stride asymmetries. The contact duration for the trailing (right) fore limb on the left lead exceeded the contact duration for the trailing (left) fore limb on the right lead. Selecting the right fore limb as the trailing fore limb may have allowed horses to use it to withstand the greater stresses and caused them to preferentially gallop with the left fore limb leading. Laterality may have an important influence on equine gallop motion patterns and thereby influence athletic performance.
Article
A simple two-allele Mendelian model of the genetics of handedness is described and fitted to data in the literature. The model proposes that there are two alleles, D (dextral) and C (chance), the homozygous DD genotype producing only right-handers (directional asymmetry), the homozygous CC genotype producing a racemic mixture of 50% right-handers and 50% left-handers (fluctuating asymmetry), and the heterozygote, DC, being intermediate between the homozygotes and producing 25% left-handers, and 75% right-handers. It is also suggested that the true population incidence of left-handedness is 7.75%, deviations from this figure being due to either criterion shifts or selection biases. The same model is then fitted, by means of a number of minor conceptual extensions, to data from the literature on the relationship of handedness to language dominance, acute and permanent aphasia, and visual processing dominance.
Article
Studies of hair follicle development and scalp hair patterning in normal persons coupled with observations of aberrant scalp hair patterning in a variety of disorders of early brain and craniofacial development are indicative of the following hypothesis: Scalp hair patterning is determined at 10 to 16 weeks of fetal life and is secondary to the growth and shape of tissues which underlie the fetal skin, especially the brain. Thus aberrant scalp hair patterning may be utilized as a clinical indicator of aberrant growth and/or shape of the early fetal brain prior to 16 weeks' gestation.
Article
Of 602 rats tested for amphetamine-induced or nocturnal rotation (circling behavior), 54.8% (P less than 0.025) had right side biases. Of 292 rats tested in two-lever operant situations, 57.5% (P less than 0.02) preferred the right lever. Right-biased rats were significantly more active and had stronger side preferences than left-biased rats. It is suggested that the increase in right-sided population bias in humans, as compared to rodents, is related to a cortical asymmetry and the phylogenetic increase in cortical modulation of subcortical structures.
Article
We investigated the relations among mental rotations and spatial perception abilities, handedness, and sexual orientation in both men and women. The present study included a relatively large sample and attempted to control statistically for important covariates such as general intelligence. Significant sex differences were obtained for mental rotations and spatial perception, but not for handedness. None of these measures was significantly related to sexual orientation within either sex.
Article
Two measures of lateralized forelimb usage, the Collins paw preference test and the Lateral Paw Preference test (LPP), were tested in 693 mice of 29 inbred strains and F1 crosses, and 2 embryo transfer groups. These strains included NZB, SM, and the NXSM recombinant inbred (RI) strains; RF and the NXRF RI strains; BXSB and the Y-consomic BXSB-Yaa+; DBA/2 and F1s of DBA/2 and BXSB and BXSB-Yaa; and NZB x NZW F1s. The findings indicated that (1) the Collins and LPP tests were independent in terms of direction of lateralization, (2) there were significant population biases of 60.96% rightward on the LPP test, and 54.39% leftward on the Collins test, (3) there were significant strain differences on measures of absolute asymmetry on both tests, (4) there were strain differences for direction of asymmetry on the Collins test, but not on LPP, (5) on the basis of the NXSM RI strains, 3 genetic loci contribute to strength of laterality on the LPP test, and (6) there was a strong correlation among strain means for strength of lateralization on the two tests. These results extend previous findings on the strength and direction of laterality, showing that two independent systems for direction of laterality may depend on the same mechanism for magnitude, and establish that multiple factors of handedness, previously identified in humans and other primates, also exist in mice.
Article
The current study extends previous documentation of behavioral asymmetries in hand-to-mouth, self-consoling behaviors of infant chimpanzees. The underlying source of lateralized hand-to-mouth, self-calming behavior was investigated by comparing individual differences in neonatal arousal levels, regulatory ability, and motor performance with individual differences in the degree of laterality at 3 months. Asymmetrical hand-to-mouth, self-calming behaviors at 3 months of age were significantly related to general arousal at 2 days of age (i.e., the Range of State cluster scores measured by the Brazelton Neonatal Behavioral Assessment Scale). Simply stated, chimpanzees with a right-hand bias in hand-to-mouth behavior exhibited lower arousal at 2 days of age compared with nonright-handed individuals. The only item of the Range of State cluster to distinguish subjects was irritability: Right-handed subjects were less irritable. Previously, a trend was reported with respect to sex differences in the laterality of hand-to-mouth behavior. With the greater number of subjects in the present study, we found that females exhibited a significantly greater right-hand bias for hand-to-mouth behaviors (12 of 13) than did males (9 of 15). We conclude that neonatal arousability, and not regulatory capacity or motor performance, predicts the degree of laterality found in hand-to-mouth, self-calming behaviors in 3-month-old chimpanzees. These data are discussed from the standpoint of early pari-parturitional or intrauterine factors affecting lateralized development.
Article
We investigated the development of lateral bias in infant tufted capuchins (Cebus apella) by recording head orientation during the first 2 postnatal weeks and hand preference during Weeks 23 to 24 and 47 to 48. We found that lateral bias for head orientation at 1 to 2 weeks was negatively related to hand preference at 23 to 24 weeks. Further, we found population-level left-hand preferences at both 23 to 24 and 47 to 48 weeks, and that hand preference at 23 to 24 weeks is positively correlated with hand preference at 47 to 48 weeks. We also noted a trend toward a sex difference in the direction of neonatal head orientation, with males exhibiting a left-side preference and females exhibiting a lack of preference toward either side. Our findings differ from those obtained in studies with developing humans and chimpanzees in two important ways. First, the trend for head orientation and hand preference in infant capuchins was to the left rather than to the right. Second, we found a negative relation between direction of early head orientation and subsequent hand preference. It seems likely that research examining cerebral development in capuchins will help us to better understand the occurrence of left-handedness and the development of cerebral dominance in humans.
Article
In this research we examined hormonal correlates of hand preference in free-ranging primates. Specifically, we tested the hypothesis that levels of the stress hormone cortisol and the male sex hormone testosterone are correlated with handedness in male rhesus macaques (Macaca mulatta). We found significant positive relationships between cortisol and testosterone levels sampled during adolescence and the frequency of right- versus left-hand use sampled during adulthood. These data indicate that adolescent measures of cortisol and testosterone are correlated with hemispheric specialization in adult free-ranging primates.
Article
Paw use on three tasks in 53 domestic dogs (Canis familiaris) was studied to determine whether the animals exhibited a significant paw preference, and, if so, to explore the direction and strength of the dogs' preferred paw use, both within, and between, tasks. The influence of the dogs' sex on their paw preferences was also explored. The findings revealed that lateralised behaviour was strongly sex related. Male and female showed paw preferences at the level of the population but in opposite directions. Female dogs had a greater preference for using their right paw on all tasks, whilst males were more inclined to adopt their left paw. Analysis revealed significant positive relationships for two of a possible three intertask correlations. Overall, the findings suggest that there are two distinct populations of paw preference in the domestic dog that cluster around the animals' sex. It is recommended that further work be conducted to explore the influence of pre-training on dogs' paw preferences before generalisations regarding laterality in this species are drawn.
Article
The objective of this study was to determine if there is an association between facial hair whorl patterns on the bovine forehead and sperm morphology. Breeding soundness exams were conducted on 219 yearling bulls at three Colorado State University facilities. There were 150 Angus bulls and the remaining bulls were of several different breeds. Hair whorl patterns on the forehead were classified as round or nonround epicenters. Angus bulls with round epicenters had a higher percentage of morphologically normal spermatozoa compared to nonround epicenters (P < 0.05). Hair whorls on Angus bulls were sorted into two extreme groups of round spirals, with rotation or long lines that were longer than the width of the eyes. Bulls with round spirals had a greater percentage of normal spermatozoa compared to bulls with long lines (P < 0.05). Hair whorl pattern on Angus bulls also had an effect on the percentage of bulls that had the minimum threshold value of 70% normal spermatozoa. Eighty percent of Angus bulls with round epicenters had > 70% or more normal spermatozoa compared to 59% with a nonround epicenter (P < 0.01). Fifty percent of Angus bulls with long lines failed because they had < 70% normal spermatozoa. There were no significant differences in the remaining non-Angus bulls. Hair whorl patterns may be useful for making early culling decisions.
Article
A study of the heritability of lobar brain volumes in twins has introduced a new approach to questions about the genetics of cerebral asymmetry. In addition to the classic comparison between monozygotic (MZ) and dizygotic (DZ) twins, a contrast was made between pairs of two right-handers (RR pairs) and pairs including one or more non-right-hander (non-RR pairs), in the light of the right shift (RS) theory of handedness. This paper explains the predictions of the RS model for pair concordance for genotype, cerebral asymmetry and handedness in healthy MZ and DZ twins. It shows how predictions for cerebral asymmetry vary between RR and non-RR pairs over a range of incidences of left-handedness. Although MZ twins are always concordant for genotype and DZ twins may be discordant, differences for handedness and cerebral asymmetry are expected to be small, consistent with the scarcity of significant effects in the literature. Marked differences between RR and non-RR pairs are predicted at all levels of incidence, the differences slightly larger in MZ than DZ pairs.
The relationship between facial hair whorls and temperament in Lundy ponies. Annual report of the Lundy Field Society
  • H Randle
  • T G Webb
  • L J Gill
Randle, H., Webb, T.G., Gill, L.J., 2003. The relationship between facial hair whorls and temperament in Lundy ponies. Annual report of the Lundy Field Society, pp. 67–83.
Training. In: Equine Behaviour. A Guide of Vet-erinarians and Equine Scientists
  • A N Mclean
  • P D Mcgreevy
McLean, A.N., McGreevy, P.D., 2004. Training. In: Equine Behaviour. A Guide of Vet-erinarians and Equine Scientists. W.B. Saunders, Edinburgh.
Basic Training of the Young Horse
  • R Klimke
Klimke, R., 1985. Basic Training of the Young Horse. J.A. Allen, London.