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The effects of relatedness, social contact, and sex on observational learning in rats (Rattus norvegicus)
Abstract
Kin recognition is the ability to identify a conspecific as a relative and can occur even when animals are complete strangers. By being able to recognise relatives, animals are able to give preferential treatment to those with which they share genes. Recognition may occur by either direct familiarisation (learning a phenotypic cue that reliably correlates to kinship), or by indirect familiarisation (learning kinship relationships through previous encounters). Rats (Rattus norvegicus) can recognise kin, however to what degree kin recognition is mediated by genetics (direct familiarisation) or social relationships (indirect familiarisation) are unknown; the influences of kinship and familiarity on the ability to learn from a conspecific is also unknown. Furthermore, the sex of an animal can also influence its ability to learn but this effect has received little attention in the literature, particularly when considering observational learning tasks. I assessed if relatedness and/or familiarity influenced a rat's ability to learn through observation, and if gender relationships influence the learning process. Eighty rats ( observers ) were given the opportunity to observe a demonstrator rat press a joystick in a given direction to obtain a food reward. Observers watched a demonstrator that had one of the following relationships with them: related and familiar, related and unfamiliar, unrelated and familiar, or unrelated and unfamiliar. When observers were given the opportunity to manipulate the joystick, the number of sniffs of the joystick, the latency to first move the joystick and the total number of presses were recorded. Rats that were both familiar and related to the demonstrator consistently performed better than any other treatment group; furthermore, rats that were familiar with the demonstrator performed the task more efficiently than rats that were not familiar with the demonstrator. When the demonstrators and observers were related, the observers produced more presses and sniffs of the joystick while having a lower latency to the first push In addition, male observers learnt better than females regardless of the demonstrator sex, with males that were familiar to their demonstrator making nearly twice as many pushes than any other treatment group. The results from this study are discussed in relation to both the mechanisms of direct and indirect recognition and the potential adaptive value on kin discrimination in the learning process. The home range hypothesis may explain why gender differences in learning were found: male rats have larger home ranges than females. Male rat will regularly encounter more rats than females and would need to ascertain if unfamiliar individuals are relatives. Females remain closer to natal sites and as such are more likely to encounter kin and therefore may not need as well as developed kin recognition ability.
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A model is presented to account for the natural selection of what is termed reciprocally altruistic behavior. The model shows how selection can operate against the cheater (non-reciprocator) in the system. Three instances of altruistic behavior are discussed, the evolution of which the model can explain: (1) behavior involved in cleaning symbioses; (2) warning cries in birds; and (3) human reciprocal altruism. Regarding human reciprocal altruism, it is shown that the details of the psychological system that regulates this altruism can be explained by the model. Specifically, friendship, dislike, moralistic aggression, gratitude, sympathy, trust, suspicion, trustworthiness, aspects of guilt, and some forms of dishonesty and hypocrisy can be explained as important adaptations to regulate the altruistic system. Each individual human is seen as possessing altruistic and cheating tendencies, the expression of which is sensitive to developmental variables that were selected to set the tendencies at a balance ap...
In recent experiments in which the social influences on feeding in Mongolian gerbils were investigated, observer gerbils acquired
food preferences from conspecific demonstrators only if the demonstrators and observers were either related or familiar. Even
then, the effects of demonstrator gerbils on observers’ food choices lasted less than 24 h. In similar experiments with Norway
rats, the familiarity/relatedness of demonstrators and observers had little effect on social learning, and the demonstrators’
influence on observers’ food choices lasted many days. We examined the causes of these differences and found that, after observer
gerbils interacted with either unfamiliar or familiar conspecific demonstrators that had been fed using procedures typically
used to feed demonstrator rats, they showed long-lasting social learning about foods, whereas observer rats interacting with
conspecific demonstrators that had been fed as demonstrator gerbils normally are fed showed effects of familiarity/relatedness
to demonstrators on their social learning about foods. Procedural differences, rather than species differences, seem to be
responsible for reported inconsistencies in social learning about foods by rats and gerbils.
Behavioural ecologists have long assumed that animals discriminate between their kin and non-kin, but paid little attention to how animals recognize their relatives. Although the first papers on kin recognition mechanisms appeared barely 10 years ago, studies now appear frequently in journals of animal behaviour. Initial findings reveal that kin recognition abilities are surprisingly well-distributed throughout the animal kingdom. Yet an understanding of the evolutionary and ecological significance of these abilities demands further analyses of the components of kin recognition mechanisms and the social contexts in which they are expressed. Many controversies and unresolved issues remain, and experimental approaches to these problems promise to continue making kin recognition an important, rapidly moving discipline within behavioural ecology.
The hypothesis that sex differences in maze learning result from sex differences in activity was tested with wild-caught prairie (Microtus ochrogaster) and meadow (M. pennsylvanicus) voles. For 38 voles error production and activity were simultaneously measured in a series of 7 symmetrical mazes. Repeated-measures analyses of variance (ANOVAS) examined species, sex, maze, and interaction effects for 3 dependent variables: errors, activity, and errors/activity. The pattern of significant effects was very different for the errors and activity ANOVAS, which suggests that differential activity cannot explain differential error rates. In contrast, the pattern of effects was very similar for errors and errors/activity ANOVAS, which suggests that controls for activity do not remove differences in error production. These results fail to support the activity hypothesis.
Mice can recognize one another by individually characteristic body scents that reflect their genetic constitution at the extremely polymorphic major histocompatibility complex (MHC) of genes on chromosome 17. Reproductive behavioral manifestations of this sensory communication system include MHC-related mating preferences and neuroendocrine responses that affect preimplantation pregnancy and arise from the MHC-related scent of alien males. We have shown previously that mice can be trained in a Y maze to distinguish the scents of urine of congeneic mice that differ genetically only at the MHC. By means of an automated olfactometer, we now show that rats also can similarly distinguish the urinary scents of MHC congeneic mice. Thus, the mode of individual recognition that depends on scents determined by MHC genes can operate across species barriers.
Spatial learning in photoperiodically induced breeding (reproductive) and non-breeding (non-reproductive) adult male and female deer mice (Peromyscus maniculatus) was examined in a Morris water-maze task. Sexually mature, adult male and female deer mice that were derived from either a mainland population (P. m. artemisiae) or an island population (P. m. angustus) were required to learn the spatial position of a hidden, submerged platform in a water maze. Deer mice were tested either during the breeding season (summer; long day photoperiod) or during the non-breeding season (winter; short day photoperiod) with a total of six blocks of four trials conducted in a single day. Retention was tested with two probe trials which occurred one and three days after acquisition. During the breeding season male spatial task acquisition was superior to female spatial task acquisition for both populations. In contrast, during the non-breeding season there were no significant sex differences in spatial acquisition for either population. This change in sexually dimorphic spatial learning was due to female spatial-performance decreasing from non-breeding season to the breeding season and male spatial-performance increasing over the same period. Both populations displayed similar seasonal variations in sexually dimorphic water-maze task performance. There were, however, overall population differences in water-maze task performance that were related to the ecology of the mice, with the insular mice displaying shorter latencies to reach the hidden platform than did the mainland deer mice.(ABSTRACT TRUNCATED AT 250 WORDS)
Sexual dimorphism in spatial and cued navigation using the Morris water maze was examined in C57BL/6 mice both with and without administration of scopolamine, a cholinergic blocker. In Exp. 1, female and male mice learned to perform first a spatial, then a cued, navigation task. Both performed a spatial task similarly; males, however, performed a cued task better than females. In Exp. 2, the sequence of navigation testing was reversed. Both performed similarly on a cued task; however, males performed a spatial task better than females. In both experiments, females were more sensitive than males to the effects of scopolamine. No significant confounding sex differences were found in either spontaneous activity or passive avoidance retention. These data indicate that sex differences in spatial and cued tasks are dependent on the sequence of task presentation and implicate a role for the cholinergic system in these differences.
Sex differences in rats' performance on a stationary hidden-platform task (spatial task) in the Morris water maze and the effects of initial nonstationary hidden platform training (NSP training) were examined. The NSP training was designed to familiarize rats with the general requirements of the water-maze task without providing spatial information. NSP training led to faster acquisition and improved retention of the subsequent spatial task in both males and females. There was a sex difference favoring males on acquisition and retention of the spatial task only in rats that had not received previous NSP training. Moreover, there was an apparent reversed sex difference favoring females on some measures of spatial performance in NSP-trained rats. These results suggest that performance on the water-maze task, including the expression of sex differences, can be altered by previous familiarization with nonspatial aspects of the task.
Recent evidence has demonstrated that there are fluctuations in both the anatomy and physiology of the hippocampus across the estrous cycle of the female rat. In the present study we examined the behavioral implications of these changes by testing females on either a hippocampal or nonhippocampal version of the Morris water maze during the various phases of the estrous cycle. Males were also tested on these tasks. Although there was little variance on the nonhippocampal cue task, females in proestrus performed significantly better than those in estrus. Optimal female performance on the spatial version of the task occurred during the phase of estrus, whereas the least efficient performance occurred during proestrus. These results do not support the traditional view that hippocampal long-term potentiation is positively correlated with spatial learning.
The hypothesis of kin recognition by phenotype matching predicts that relatives can be identified without previous contact, and/or that cues used for recognition can be learned indirectly from a third but related individual. This hypothesis was tested in the field using 22 beaver, Castor canadensisfamilies. Individually identifiable beavers were provided with a two-way choice between two experimental scent mounds, one of which was scented with the anal gland secretion (AGS) from an unfamiliar sibling of the test subjects, the other with AGS from an unfamiliar non-relative. Beavers showed less strong territorial responses to AGS from their siblings than to that from non-relatives. The mates of the test subjects, which were not related to, or familiar with, either of the AGS donors, also responded less strongly to the AGS from their mates' siblings than to that from other unfamiliar non-relatives. This discrimination was not shown when castoreum samples were tested instead of AGS. Therefore, it was concluded that (1) information about kinship in the beaver is coded in the AGS but not in the castoreum, (2) the mechanism of phenotype matching is used in beaver sibling recognition, and (3) the cue used in phenotype matching can be learned and used for recognition of related individuals by an unrelated individual.1997The Association for the Study of Animal Behaviour
It is widely believed that male mammals have better spatial ability than females. A large number of evolutionary hypotheses have been proposed to explain these differences, but few species have been tested. The authors critically review the proposed evolutionary explanations for sex differences in spatial cognition and conclude that most of the hypotheses are either logically flawed or, as yet, have no substantial support. Few of the data exclusively support or exclude any current hypotheses. The hypothesis with the strongest support proposes that range size was the selection pressure that acted to increase spatial ability. The authors suggest ways in which these hypotheses could be tested by presenting explicit predictions and suggesting suitable test species or conditions.
The present studies examined sex differences in object localization and recognition in C57BL/6 mice. Experiment 1 measured responses to spatial novelty (object displacement) and object novelty (object substitution). Males strongly preferred displaced and substituted objects over unchanged objects, whereas females showed a preference in only 1 measure of object novelty. Experiment 2 further examined object recognition by presenting mice with 2 identical objects, followed 24 hr or 7 days later by testing with a familiar and a novel object. After 24 hr, males preferentially explored the novel object, whereas females exhibited no such preference. Neither sex displayed a preference for the novel object after 7 days. The data suggest that male mice are superior to females at localizing and recognizing objects.
Rats, Rattus norvegicus, familiar with maze procedures reliably followed conspecific leaders in a maze. Rats trained to follow in a maze followed leaders that had eaten a food known to the follower to be safe, with higher probability than they followed leaders that had eaten a food known to the follower to be poisonous. Thus, rats have the capacity both to follow conspecifics to feeding sites and to choose conspecifics to follow on the basis of the desirability of the foods those conspecifics have been eating. These findings are consistent with the hypothesis that aggregation sites of rats in natural environments might serve as information centres where unsuccessful, foragers could select more successful colony-mates to follow to food.
Kin recognition, the ability to identify and respond differentially to one's genetic relatives, is one of the fastest growing and most exciting areas of ethology. Dr Hepper has brought together leading researchers in the field to create a thought-provoking and critical analysis of our current knowledge of the phenomenon, with particular emphasis on the underlying processes involved, and their significance for the evolution of social behaviour. Students of animal behaviour and evolutionary biology will find this book an invaluable source of information and ideas.
In studying the cues used in kin recognition, two sets of questions need to be addressed: 1) whether the cues used for recognition are phenotypic labels shared by all genetic relatives (eg a family-specific label), or whether such cues are individually distinctive and, as such, provide no direct information on the genetic relatedness of conspecifics; and 2) whether the sensory cues used for kin recognition have a genetic basis or are environmentally acquired. The sensory modalities used for parent-offspring and sibling recognition among different vertebrate groups and species are also reviewed. -from Author
The effect of observational learning on the acquisition of an operant response was examined in eighteen riding horses and ponies. The test horses were randomly divided into three groups of six and individually exposed to one of three treatments. An additional horse was trained as a demonstrator, to perform the operant response. The observer horses watched either the demonstrator performing the bin-opening response (Group D+B); the demonstrator standing passively (Group D); or the operant bin in the absence of the demonstrator (Group B). Observers had access to and were free to interact with an identical bin during testing. Observers in Groups D+B and D were socially familiar with the demonstrator. Each test horse was tested once a day for 10 days. An ANOVA revealed no significant differences between treatment groups in the number of responses or the time taken to reach the learning criterion. However, there were highly significant differences between breed types, with non-warmbloods performing more bouts of opening the bin and feeding (p=0.02), feeding from the bin sooner (p=0.01) and reaching the criterion for learning sooner than warmbloods (p=0.05). There was also a significant negative linear relationship between horses' ages and time spent investigating the bin, with younger horses performing more investigative behaviour (y=−3.08x+106.86; p=0.02).
Describes recent work on the theoretical and empirical issues relevant to animal kin recognition and outlines 4 mechanisms by which kin might be identified: (1) spatial distribution, (2) association, (3) phenotype matching, and (4) recognition alleles. It is suggested that kin recognition is usually based on spatial distribution or direct association during rearing. Phenotype matching is proposed as an additional mechanism that could facilitate recognition between relatives who have not previously associated with each other. (65 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Many sex differences are likely to be adaptive consequences of sexual selection. Sex differences in spatial ability are well described for Homo sapiens and laboratory rodents, and such cognitive traits may also be shaped by sexual selection. An evolutionary model is outlined to predict the distribution of these sex differences across species. Sex differences in spatial ability were previously believed to be universal among mammals, but the evolutionary model has correctly predicted that such differences will evolve only in species where mobility has different effects on male and female fitness.
Wild microtine rodents are particularly useful for testing this model. Radiotelemetric data from field studies of ranging behavior, data from laboratory studies of maze learning, and neuroanatomical data on the hippocampus, a structure believed to be critically involved in spatial processing, all support the model. Several alternative explanations for sex differences in spatial ability are reviewed and evaluated. The proximate developmental basis of these sex differences is discussed, and an attempt is made to integrate developmental and evolutionary perspectives. Several promising future research directions are outlined.
ross-fostering techniques in which infants are taken from their genetic parents and reared by unrelated foster parents have been widely used in behavioural research to investigate several developmental questions. Here we address some of the central issues involved in using cross-fostering to study kin recognition where it has been applied frequently. We do so by first outlining general principles of recognition mechanisms, and then presenting three different cross-fostering designs that allow researchers to examine specific details of the de- velopment of recognition abilities. Our discussion focuses on kin recognition, although the transfer of young between litters, broods or clutches is a commonly used tool for other behavioural questions, including vocal development in primates (Owren et al. 1993) and birds
Bacterial contents of both the anal gland and castor gland of the beaver (Castor canadensis) were determined. Using our culture methods, no bacteria were isolated from the castor glands, but the anal gland contained high numbers of the aerobeEscherichia coli and the anaerobeBacteroides fragilis. The latter may be represented by several variants but facilities were not available for advanced anaerobic analysis. The relative numbers of each bacterial group and the group present were constant regardless of sex, age class, or colony of beaver. The bacterial fermentation hypothesis is rejected for castor gland section but remains possible for anal gland secretions based on variations seen inB. fragilis. The role of the products of both the castor gland and anal gland are discussed in relationship to scent communication in beaver.
Putrescine (1,4-diaminobutane) and cadaverine (1,5-di-aminopentane) were identified in the anal sac secretions of the red fox,Vulpes vulpes, and of the lion, Panthera leo. Anal sac secretion samples obtained over a period of 10 weeks by sampling from within each sac of each of 6 captive foxes were analyzed and putrescine, cadaverine, and volatile fatty acid compositions and secretion pH values recorded. A significant (P < 0.001)="" negative="" correlation="" of="" ph="" (range="" 6.5–9.4)="" with="" total="" volatile="" fatty="" acid="" concentration="" was="" observed.="" secretion="" compositions="" are="" discussed="" in="" the="" context="" of="" a="" fermentation="" hypothesis="" of="" chemical="" recognition.="" secretion="" samples="" could="" not="" be="" unambiguously="" assigned="" to="" particular="" foxes="" on="" the="" basis="" of="" simple="" comparisons="" of="" volatile="" fatty="" acid="" profiles="" alone.="" composition="" differences="" were="" noted="" between="" secretions="" obtained="" at="" a="" given="" time="" from="" corresponding="" right="" and="" left="">
To achieve odour-based kin recognition, rodents need olfactory cues that indicate kinship. Odour–genes covariance is a phenomenon by which closer genetic relationships between individuals are reflected in greater similarity in their odours. We tested odour–genes covariance among kin groups in Mus spicilegus. Using a habituation–generalization procedure designed to assess responses to similarities, we found that males (unrelated to any of the odour donors) recognized similarities in the odours of brothers (r = 0.5) when compared to an unrelated male. With the same protocol, we also found similarities between the odours of double cousins (r = 0.25) and cousins (r = 0.125). This demonstrates that kinship from siblings to cousins is reflected in odour similarity. To investigate the precision of animals' responses to odour similarities based on relatedness, we conducted similar tests using odours from males of different relatedness to the habituation odour donor. Mice responded to the similarities between odours of double cousins compared to cousins. This is a clear demonstration of the subtlety of odour–genes covariance among close kin. Mice did not, however, treat odours of brothers as similar compared to those of ‘super half-brothers’ (r = 0.375). We discuss the implications of these findings for differential responses based on degrees of relatedness, including kin recognition.
Rats were given a simultaneous choice of unfamiliar, same-sex, age-mate conspecifics of four different degrees of relatedness (siblings, paternal half-siblings, cousins and unrelated) and their investigation time was measured. The results revealed a linear trend between relatedness and investigation time, rats showing greater investigation as the degree of relatedness decreased. The results indicate that rats possess an identifier which can be used to discriminate different degrees of kinship. Further, this identifier is possessed by kin in direct proportion to their relatedness, i.e. siblings possess 50% of the identifier in common, cousins 12·5%, etc. The importance of the linearity of the trend for the process of phenotype matching is disucssed. The advantages of this identifier being produced by an individual's genes are considered and the possible influence of microorganisms discussed.
Hungry `observer' rats watched at trained conspecific `demonstrators' performing a duration discrimination (1 vs. 8 s sound) before being themselves exposed to the same task. Performance of `observer' rats was compared with that of naive control rats who learned the same task without observing a demonstrator. Statistical analysis showed that observing a trained demonstrator significantly contributed to the rapid discovery of the relationship between a particular duration and its related response patterns or stimuli, increasing learning speed with regard to the control animals.
Abstract. Because of changing environmental conditions, honey bee, Apis mellifera , nectar foragers must constantly assess resources. A forager's perception of resource profitability may be affected by her past foraging experience. To test this, the concentrations of sucrose solutions in feeders were varied and dance characteristics that serve as indicators of resource profitability were recorded. Round dances of foragers that had last visited a lesser concentration than that on which they were presently foraging had higher rates of directional reversal, circuit rates and speeds than those of foragers on the same concentration that had last visited a feeder offering a higher sucrose concentration. Dance information related to resource profitability was thus modulated by the immediate past experience of a forager, and was not based strictly on absolute resource profitability. Losses were weighted more heavily than gains. Contrary to the assumptions of current models of optimal prey choice, past foraging experience can influence resource assessment.
Previous experiments have shown that some strains of mice prefer mates with a major histocompatibilty complex (MHC) that differs from their own, and urine has been suggested as the olfactory signal used for discrimination. Similarly, it has been proposed that females use MHC-associated cues to choose female nesting partners. The objective of the present study was to clarify the role of urinary odours in recognition of MHC-similar and -dissimilar mice by testing odour preferences of female mice. We used B10 (H-2b) and B10.Q (H-2q) mice that differ only at the MHC loci. Our hypothesis that female mice would spend more time exploring the urinary odours of MHC-similar females, a mechanism thought to account for communal nesting patterns, was not supported; both strains explored MHC-similar and -dissimilar urinary odours equally. Our hypothesis that females would prefer the urinary odours of MHC-disparate males, as an indication of mate choice, was also not supported; neither B10 nor B10.Q females showed a significant preference for the MHC-dissimilar odour. Finally, we determined whether infection with the intestinal nematode, Heligmosomoides polygyrus, would alter urinary odour preferences. Our supposition that females would prefer the urinary odours of uninfected males, regardless of MHC strain, was supported; both B10 and B10.Q females demonstrated a significant preference for B10 uninfected male urine. Our results suggest that chemical communication through urine may not play as dominant a role in selection of nesting partners and mates as previously thought, but that it may be very important in conveying infection status.
A laboratory experiment was conducted in order to explore the possibility of imitation, that is, response learning by observation, in marmosets,Callithrix jacchusInexperienced individuals were allowed to observe a skilful model that demonstrated one of two possible techniques (pushing or pulling a pendulum-door) to get food from inside a wooden box. Their initial manipulative actions, performed when exposed to the box in a subsequent test, were compared with those of naive control subjects (non-observers). The observers showed less exploratory behaviour than the non-observers and, more importantly, some showed a strong tendency to use the demonstrated opening technique in the initial test phase. This initial preference disappeared in the course of five test sessions and the observers converged towards the simpler, alternative solution that was generally preferred by the non-observers. Despite fundamental individual differences in the observer group and the failure to find a significant group effect, the results indicate that marmosets are capable of learning simple motor skills through conspecific observation.
This study was an attempt to determine whether sibling recognition in P. leucopus is mediated by phenotype matching or by association. A measure of social preference in a two-way choice apparatus was used to infer sibling recognition. Experiment 1 demonstrated that, when given a choice in the preference apparatus, adult mice spent significantly more time on the side with a familiar sibling (a sibling that had been reared together with the test animal) than on the side with an unfamiliar non-sibling (a non-sibling that had been reared apart from the test animal). In experiment 2, pups were cross-fostered within the first 3 days of birth such that four combinations of sibship and association were formed: siblings reared together, siblings reared apart, non-siblings reared together, non-siblings reared apart. Mice showed a significant preference for siblings reared together versus siblings reared apart, and for non-siblings reared together as compared to siblings reared apart. There were no significant differences in time spent near siblings reared together versus non-siblings reared together, nor between siblings reared apart versus non-siblings reared apart. These results demonstrate that association during early life, and not genetic relatedness per se, is the most important factor mediating sibling recognition and preference in this species. It is suggested that the major difference between phenotype matching and recognition by association is that, in the former case, animals learn family-specific identification cues, while in the latter, they learn individually-distinctive cues that cannot be generalized to unfamiliar relatives.
SYNOPSIS. We report results of a three year comparative laboratory study of kin recognition abilities in Arctic ground squirrels ( Spermophilus parryii ) and Belding's ground squirrels ( S. beldingi ), and a field investigation of kin recognition in S. beldingi . Our laboratory work shows that in both species, preweaned pups reared together, whether they are biological siblings or cross-fostered (unrelated) nestmates, are equally aggressive in subsequent paired arena tests. Thus, pups that share a natal nest are treated like siblings. Among pups reared apart, sister-sister pairs are less aggressive in arena tests than are pairs of nonkin females, whereas relatedness does not affect male-male or male-female aggression. Thus both relatedness and rearing environment mediate recognition among female S. parryii and S. beldingi . In free-living Belding's ground squirrels at Tioga Pass, California, dam-offspring and sister-sister recognition apparently first occur at weaning, coincident with aboveground emergence of juveniles. Most intriguing (electrophoretically identified) littermate full-sisters and maternal half-sisters, which result from multiple mating by females, seem to treat each other differently despite having shared a natal nest. The full-sisters are less agonistic and more cooperative than the half-sisters. In interpreting these laboratory and field results, we explore four proximal mechanisms by which kin might be identified, including one in which recognition is based on (learned) phenotypic similarity to an individual's nestmates or itself (phenotype matching). Our data and those of several recent investigators of recognition in other taxa implicate both association with relatives and phenotype matching in the ontogeny of kin recognition.
Social learning where an "individual's behavior is influenced by observation of, or interaction with, another animal or its products" has been extensively documented in a broad variety of species, including humans. Social learning occurs within the complex framework of an animal's social interactions that are markedly affected by factors such as dominance hierarchies, family bonds, age, and sex of the interacting individuals. Moreover, it is clear that social learning is influenced not only by important sexually dimorphic social constraints but also that it involves attention, motivational, and perceptual mechanisms, all of which exhibit substantial male-female differences. Although sex differences have been demonstrated in a wide range of cognitive and behavioral processes, investigations of male-female differences in social learning and its neurobiological substrates have been largely neglected. As such, sex differences in social learning and its neurobiological substrates merit increased attention. This review briefly considers various aspects of the study of social learning in mammals, and indicates where male-female differences have either been described, neglected and, or could have a potential impact. It also describes the results of neurobiological investigations of social learning and considers the relevance of these findings to other sexually dimorphic cognitive processes.
Preweanling and postweaning offspring of gerbil parents fed Purina Laboratory Chow or Pooch dog food show selective preference for odors coming from other animals of these same diets. Odors with differential quality include whole animal, cage material and ventral scent gland sebum. Apparently diet alters chemosignals, even those from a specialized scent gland. Species-specific pheromones may be dependent on ingested foodstuffs or other ecological chemicals.
Despite widespread interest in kin selection and nepotism, relatively little is known about the perceptual abilities of animals to recognize their relatives. Here I show that a highly nepotistic species, Belding's ground squirrels (Spermophilus beldingi), produces odours from at least two sources that correlate with relatedness ('kin labels'), and that ground squirrels can use these odours to make accurate discriminations among never before encountered ('unfamiliar') kin. Recognition odours appear to vary linearly with relatedness, rather than in an all-or-none fashion, allowing precise estimates of kinship even among distant relatives. Thus S. beldingi are able to recognize their distant kin and male kin, even though they do not treat them preferentially. I also show that a closely related species (S. lateralis) similarly produces kin labels and discriminates among kin, although it shows no evidence of kin-directed behaviour. Thus, contrary to a commonly held assumption, kin favouritism and recognition abilities can evolve independently, depending on variation in the costs and benefits of nepotism for a given species.
The existence of sex differences in the standard rat and mouse models of learning and memory is a controversial and contested topic in the literature. The present meta-analysis of radial maze and water maze experiments was conducted to assess the reliablility and magnitude of sex effects in the standard rodent models of learning and memory. Data were culled from published and unpublished sources. Findings indicate large reliable male advantages for rats in radial maze and water maze protocols. Significant strain differences were also identified. In each paradigm, protocol variations were associated with differential sex effects. For the water maze, smaller male advantages were associated with pretraining regimens and for the radial maze, larger significant male advantages were observed in protocols that included unbaited arms (combined reference and working memory protocols). Mouse studies exhibited a different pattern of sex effects; small female advantages were evident in the water maze, but small male advantages were evident in the radial maze. Together these findings establish the reliability of male advantages in spatial working and reference memory for rats across strains, protocols, ages and rearing environments. The findings also support an important species dichotomy between rats and mice that should be considered when transitioning from rat to mouse models. In light of these results, the biological evidence supporting theoretical explanations of sex differences is reviewed and evaluated.
The Ecology and Sociology of the Norway Rat. Bethesda, MD: U.S. Department of Health, Education and Welfare. r80 Choleris Social learning in animals: sex differences and neurobiological analysis
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Maternal 'imprinting' in goats A classification and review of cooperation procedures
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Social enhancement of odor preference in rats: Is there something special about odors associated with foods
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Imitation in animals: Evidence, function and mechanisms Avian visual cognition [On-line]. Available: www.pigeon.psy.tufts Kinship, kin discrimination and mate choice
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