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If I fits I sits: A citizen science investigation into illusory contour susceptibility in domestic cats (Felis silvestris catus)
Abstract
A well-known phenomenon to cat owners is the tendency of their cats to sit in enclosed spaces such as boxes, laundry baskets, and even shape outlines taped on the floor. This investigative study asks whether domestic cats (Felis silvestris catus) are also susceptible to sitting in enclosures that are illusory in nature, utilizing cats’ attraction to box-like spaces to assess their perception of the Kanizsa square visual illusion. Carried out during the COVID-19 pandemic, this study randomly assigned citizen science participants Booklets of six randomized, counterbalanced daily stimuli to print out, prepare, and place on the floor in pairs. Owners observed and videorecorded their cats’ behavior with the stimuli and reported findings from home over the course of the six daily trials. This study ultimately reached over 500 pet cats and cat owners, and of those, 30 completed all of the study’s trials. Of these, nine cat subjects selected at least one stimulus by sitting within the contours (illusory or otherwise) with all limbs for at least three seconds. This study revealed that cats selected the Kanizsa illusion just as often as the square and more often than the control, indicating that domestic cats may treat the subjective Kanizsa contours as they do real contours. Given the drawbacks of citizen science projects such as participant attrition, future research would benefit from replicating this study in controlled settings. To the best of our knowledge, this investigation is the first of its kind in three regards: a citizen science study of cat cognition; a formal examination into cats’ attraction to 2D rather than 3D enclosures; and study into cats’ susceptibility to illusory contours in an ecologically relevant paradigm. This study demonstrates the potential of more ecologically valid study of pet cats, and more broadly provides an interesting new perspective into cat visual perception research.
... own pet, has some significant potential advantages over studies conducted in a laboratory environment, such as providing larger samples and more naturalistic data by collecting the data in the animal's daily environment (Smith et al. 2021(Smith et al. , 2022Stewart et al. 2015). In addition, the ubiquity of dogs around the world also provides a wealth of opportunities for humans to observe and interact with dogs and to explore learning in non-human animals (ManyDogs Project et al. 2023). ...
... Further, with these approaches, subsequent re-coding or verification of the Animal Cognition owner's experimental procedure and inputted results is impossible because the only data experimenters have access to is input by guardians. Because of this limitation, some citizen science projects have used the second major variant, asking guardians to submit video data of the experiment to be coded by a researcher (Hecht and Spicer Rice 2015;Smith et al. 2021Smith et al. , 2022. This has the advantage of providing strict quality control on the data used. ...
... This may impact performance and overall data quality (Smith et al. 2022). There are also limited controls when guardians act as active experimenters (e.g., are actively presenting stimuli as seen in Stewart et al. (2015) vs. recording responses to stable stimuli like in Smith et al. (2021Smith et al. ( ,2022. Guardians typically receive written and/ or video instructions, which can be misunderstood. ...
Citizen science approaches have grown in popularity over the years, partly due to their ability to reach a wider audience and produce more generalizable samples. In dogs, these studies, though, have been limited in their controls over materials or experimental protocols, with guardians typically reporting results without researcher supervision. Over two studies, we explored and validated a synchronous citizen science approach. We had dog guardians act as experimenters while being supervised by a researcher over Zoom. In study 1, we demonstrated that synchronous citizen science produced equivalent levels of performance to in-lab designs in a choice task. Consistent with past in-lab research, dogs selected a treat (vs. an empty plate) in a two-alternative forced-choice task. In study 2, we showed that Zoom methods are also appropriate for studies utilizing looking time measures. We explored dogs’ looking behaviors when a bag of treats was placed in an unreachable location, and dogs’ guardians were either attentive or inattentive while dogs attempted to retrieve the treats. Consistent with past work, dogs in the attentive condition looked at their guardian for longer periods and had a shorter latency to first look than dogs in the inattentive condition. Overall, we have demonstrated that synchronous citizen science studies with dogs are feasible and produce valid results consistent with those found in a typical lab setting.
... In applied ethology, the citizen science approach enables for investigation of domestic animals' behaviors and leverages the experience of caretakers (Smith et al., 2021). Most studies use videos, photos, surveys, notes, and even a diary of behaviors (Gillies and Clout, 2003;Fugazza et al., 2021;Laverack et al., 2021). ...
... It is known that they tend not to behave naturally and most of them will be very frightened (Amat et al., 2015). One good example is a cat cognition study carried out using citizen science approach during the Covid-19 pandemic (Smith et al., 2021). This study explored the tendency cats have to sit in enclosed spaces, such as boxes and baskets, and investigated whether cats sat in illusory enclosures, such as two-dimensional geometric shapes on the floor made with a piece of paper. ...
... In a previous study of Smith et al. (2021), which did not include a synchronous researcher and relied on participants recording themselves instead, 21 out of 30 participants did not follow instructions properly. In comparison, all 48 of our participants met the criteria for inclusion and analysis, thus demonstrating that our method ensures lower loss of individuals due to researcher's monitoring throughout the session. ...
Owing to restrictions imposed by the COVID-19 pandemic, numerous animal behavior studies incorporated elements of citizen science and/or were conducted remotely through online video calls. For the current cognition study about communication of domestic cats, the authors added an element of synchronicity to the citizen science approach. Considering cats are territorial and do not usually leave their homes with their owners, Synchronous citizen science, as the authors designated their innovative approach, proved to be extremely beneficial. To adjust the method, five pilot trials (five cat-owner dyads) were conducted, followed by a subsequent sample with 48 cat-owner dyads. Internet access and a free video call app were required for participation as the experiment was to be conducted during an online video call scheduled at the most convenient time for the cat-owner dyad. Before the experiment, a script detailing the procedure to be followed was sent to the participants. During the video call, two types of interactions were recorded: feeding and playing. In the first scenario, the cat would be offered their favorite food for up to five seconds. Then, the owner would restrict access by holding the feeder for 60 s, after which they would offer the food to the cat once again. In the second scenario, the owner would initiate a playing session using a new wand toy sent to them by the authors. The owner would play with the cat for 40 s, cease interaction for 60 s, and resume playing for 40 s. The interactions lasted two and four minutes, respectively, and were monitored by the researcher, who could guide the participant in the experiment, if needed. This short communication aims at presenting this new methodology, developed and refined in the pilot sample of five dyads. After the first round of experiments discussed here, the authors replicated the procedure with a full sample of 48 dyads and achieved high success and data reliability. Prioritizing humans' and cats’ welfare during the COVID-19 pandemic called for creative research methods, which eventually led to exciting paths in terms of analyzing cat behavior in their familiar environment with minimal disturbances.
... To safely test animals during the COVID-19 pandemic, we recruited participants in a community science method identical to the procedure of G. E. Smith et al. (2021). Community science is a useful method to include participants unable to come to a research facility (e.g., fearful, or aggressive dogs), but also to test pets in an environment where they are likely to behave in a naturalistic manner. ...
... ful method to include participants unable to come to a research facility (e.g., fearful, or aggressive dogs), but also to test pets in an environment where they are likely to behave in a naturalistic manner. Community science is further ideal for studying domestic cats, as many cats become severely stressed in novel environments (Amat et al., 2016;G. E. Smith et al., 2021). ...
Within human–animal dyadic interactions, dog–human gaze has been identified as the crux of several important visual behaviors, such as looking back, gaze-following, and participation in an oxytocin feedback loop. It has been posited that this gaze behavior may have been motivated and sustained by cooperative relationships between dogs (Canis lupus familiaris) and humans (e.g., hunting, service roles), however, to investigate why gaze evolved, a comparison to a domesticated species that lacks a protracted history of cooperative companionship is needed: the domestic cat (Felis catus). In this study, we compare the gaze duration to owners of cats and dogs in a community science setting. We replicated previous gaze studies with dogs, wolves (Nagasawa et al., 2015), and dingoes (Johnston et al., 2017), requesting owners to sit with their pets for 5 min and interact as they normally would. Cats and dogs gazed at their owners for similar durations, but durations of petting and physical contact were significantly lower with cats. Gaze correlated significantly with vocalizations in dogs; however, no other correlations were significant. Dogs gazed less in our community science setting than dogs tested previously in-lab (Nagasawa et al., 2015). Ultimately, cats resemble dogs in their general gaze patterns, but not in most interactions with their owner. Future research should aim to include feral cats or wild cat species to shed light on gaze behavior development in the genus, while more community science work can identify the behaviors that shift for dogs between familiar and unfamiliar environments.
... An alternative experimental method involves spontaneous choice, in which an individual exhibits attraction to an illusion due to its biological relevance (most often food). A study by Smith et al. (2020) [10] re-examined domestic cats' perception of the Kanizsa square by presenting cats with the illusion, a square, and a control, relying on cats' attraction to enclosed spaces to determine the illusory perception. The authors found that the subjects stood/sat in the illusion as much as in the square and more than in the control, confirming that cats demonstrate a human-like susceptibility to the illusion. ...
... This four-month study took place from May to September 2021 and was adapted from Regaiolli et al.'s (2019) [17] methodology into a community science paradigm due to its efficacy in examining non-human animal behavior and cognition (e.g., [10,22,23] The three stimuli presented were: Rotating Snakes; a control stimulus with the same pattern as the illusion that does not elicit perceived motion (hereafter called Plain Snakes); and a control stimulus consisting of a simple pattern of overlapping circles that also does not elicit perceived motion (hereafter called Big Circles) ( Figure 1). The Rotating Snakes illusion consists of alternating black, blue, white, and yellow blobs (black, dark grey, white, light grey for the achromatic version). ...
Illusions—visual fields that distort perception—can inform the understanding of visual perception and its evolution. An example of one such illusion, the Rotating Snakes illusion, causes the perception of motion in a series of static concentric circles. The current study investigated pet dogs’ and cats’ perception of the Rotating Snakes illusion in a community science paradigm. The results reveal that neither species spent significantly more time at the illusion than at either of the controls, failing to indicate susceptibility to the illusion. Specific behavioral data at each stimulus reveal that the most common behaviors of both species were Inactive and Stationary, while Locomotion and Pawing were the least common, supporting the finding that susceptibility may not be present. This study is the first to examine susceptibility to the Rotating Snakes illusion in dogs, as well as to directly compare the phenomenon between dogs and cats. We suggest future studies might consider exploring alternative methods in testing susceptibility to motion illusions in non-human animals.
... The cat (Felis catus) is a species that retained its original hunting skills as a domesticated mesopredator, 8 however, it also widely shares the anthropogenic niche with humans as one of the most successful companion animals. 9 There is accumulating evidence about cats' capacity for complex cognition, for example, they performed successfully in the so-called ''Kanizsa-square'' paradigm 10 ; and cats were also capable of spontaneous quantity-discrimination (adult cats, 11 kittens 12 ). Moreover, perhaps as a sign of evolutionary adaptation to their new social environment, cats show remarkable performance in many tasks involving social cognition: they can follow human visual signals, such as gazing, 13 respond to ostensive cues, 14 and prefer cat-directed speech patterns. ...
Various animal species can make a priori decisions about the passability of openings, based on their own size knowledge. So far no one has tested the ability for self-representation in cats. We hypothesized that cats may rely on their size awareness when they have to negotiate small openings. Companion cats (N = 30) were tested with incrementally decreasing sized openings, which were either the same height, or the same width. Cats approached and entered even the narrowest openings, but they slowed down before reaching, and while passing through the shortest ones. Because of their specific anatomical features and cautious locomotory strategy, cats readily opt for the trial-and-error method to negotiate narrow apertures, but they seemingly rely on their body-size representing capacity in the case of uncomfortably short openings. Ecologically valid methodologies can provide answers in the future as to whether cats would rely on their body awareness in other challenging spatial tasks.
... For example, Kanizsa triangles (Figure 3b) produce the illusion of a bright triangle via the use of fragmented Pac-man-like stimuli, none of which fully outline the perceived shape. Research in nonhuman animals has revealed that illusory contours such as Kanizsa figures are perceived by cats (Smith et al. 2021), mice (Okuyama-Uchimura & Komai 2016), goldfish (Wyzisk & Neumeyer 2007), cuttlefish (Zylinski et al. 2012), and bees (Horridge et al. 2022) but not rats (Minini & Jeffery 2006). This taxonomic diversity suggests a general benefit of heuristics that support shape detection and boundary completion during object perception, perhaps especially in spatially complex environments where shape-diagnostic edges may be interrupted by visual obstructions (Peterhans & Von Der Heydt 1991). ...
Animals live in visually complex environments. As a result, visual systems have evolved mechanisms that simplify visual processing and allow animals to focus on the information that is most relevant to adaptive decision making. This review explores two key mechanisms that animals use to efficiently process visual information: categorization and specialization. Categorization occurs when an animal's perceptual system sorts continuously varying stimuli into a set of discrete categories. Specialization occurs when particular classes of stimuli are processed using distinct cognitive operations that are not used for other classes of stimuli. We also describe a nonadaptive consequence of simplifying heuristics: visual illusions, where visual perception consistently misleads the viewer about the state of the external world or objects within it. We take an explicitly comparative approach by exploring similarities and differences in visual cognition across human and nonhuman taxa. Considering areas of convergence and divergence across taxa provides insight into the evolution and function of visual systems and associated perceptual strategies.
... The use of a video recorded by a small video camera attached to the collar around the neck of the pet. video-based approach for analysing cat-cat interactions and dynamics, although the methodology has been used for other research topics in cat behavioural research including cognition (Smith et al., 2021) and communication (Fukimoto et al., 2023). Videos recorded by lay people have also been used in behavioural research in other species, including dogs (e.g. ...
Citizen science, which involves engaging the general public in research tasks, is increasingly used in animal behaviour studies. In this review we conducted a SWOT analysis (Strengths, Weaknesses, Opportunities, Threats) to evaluate two methodologies of data collection using citizen science in order to study cat-cat interactions: online survey responses and caregiver-recorded home videos analysed by researcher(s). Using the SWOT-analysis on both methodologies, we listed intrinsic aspects that facilitate (Strengths) or interfere with (Weaknesses) reaching scientific goals, as well as the features that the methodology may be able to capitalise on (Opportunities) or which limit its value (Threats). A major strength of online surveys is the possibility to access caregivers’ specific knowledge of their cats, while sampling bias often is a potential weakness. Opportunities of surveys are the methodology´s flexibility and data collection efficiency, but at the same time suffering from threats related to biases associated with caregiver interpretation of their pet’s behaviour. Strengths of caregiver-recorded videos capturing cats’ behaviour include that they allow expert behavioural observations and scoring in a systematic manner (e.g. using an ethogram) and thus yielding quantitative data (whose reliability can be tested between and within observers). Furthermore, given the ubiquity of smartphones, filming cats is not a burden for most caregivers, and the collected recordings can potentially contain high-quality data that may otherwise be inaccessible, or subject to bias if a researcher had been present in the home environment. Though, caregivers’ influence on and lack of standardisation of the recordings are weaknesses which possibly influence the quality of the collected data. Opportunities include public engagement with science, while possible Threats may be related to privacy of the caregivers participating. In this review we consider in more detail each of the four SWOT components related to each methodology in order to optimise cat behaviour research in the future. The authors suggest strategies for future studies using the research methodologies discussed in this review and give specific recommendations when using caregiver-recorded videos in behavioural studies. Additionally, smart combinations of both online surveys with home videos recorded by caregivers might overcome some limitations of the individual methodologies, and would thus be a potentially stronger approach.
... This relates mostly to circles 1 and 2, and somewhat to circle 3 in fig. 3 (Bird et al., 2014;Johnston et al., 2022), in general, citizen science data has been invaluable for ecological research (e.g. Border et al., 2017;Gordo et al., 2021;Greenwood, 2007;Smith et al., 2021;Sweet, Rödl, et al., 2022). The first study of this thesis is one such investigation that uses public citizen science data in addition to government-managed data. ...
This thesis aims to assess and add to the basic ecological and social-ecological knowledge within urban ecosystems. Human attitudes strongly influence the ecology of cities, and this in turn influences how people that live in cities perceive nature in cities. I addressed basic questions relating to animal biodiversity in German cities and attitudes towards the animals that are present in them. These questions relate to the apparent paucity of information on these topics in Germany, and research towards urban nature as a whole.
Link to thesis:
https://mediatum.ub.tum.de/?id=1695254
... This was probably because food rewards seemed insufficient to motivate the laboratory dogs to participate in the task, and/or their willingness to participate could have been influenced by a variety of situational factors, such as the unfamiliarity of the situation and/or the proximity of the stranger. The finding that one of the principal components, Willingness to interact, was composed of the dogs' willingness to accept food as well as behavioral variables coded in the abovementioned three tasks, clearly indicates that the degree of individual willingness to participate is one of the key challenges in testing laboratory dogs [similar to some other animals, like cats; e.g., Smith et al. (33)]. ...
For a long time, oxytocin has been thought to have a generally positive effect on social cognition and prosocial behavior; however, recent results suggested that oxytocin has beneficial effects only under certain conditions. The aim of the present study was to explore potential associations between social competence and the effect of intranasal oxytocin on the social behavior of laboratory beagle dogs. We expected oxytocin treatment to have a more pronounced positive effect on dogs with lower baseline performance in a social test battery. Thirty-six adult dogs of both sexes received 32 IU intranasal oxytocin and physiological saline (placebo) treatment in a double-blind, cross-over design, with 17–20 days between the two sessions. Forty minutes after the treatment, dogs participated in a social test battery consisting of eight situations. The situations were carried out within one session and took 20–30 min to complete. Principal component analysis on the coded behaviors identified four components (Willingness to interact, Preference for social contact, Non-aversive response to nonsocial threat, and Non-aversive response to social threat). The subjects' behavior during the placebo condition was used to assess their baseline performance. We found that oxytocin treatment had a differential effect on the behavior depending on the baseline performance of the individuals in all components, but only two treatment × baseline performance interactions remained significant in a less sensitive analysis. In accordance with our hypothesis, oxytocin administration increased dogs' contact seeking and affiliative behaviors toward humans but only for those with low baseline performance. Dogs with low baseline performance also showed significantly more positive (friendly) reactions to social threat after oxytocin administration than after placebo, while for dogs with high baseline performance, oxytocin administration led to a more negative (fearful) reaction. These results indicate that similar to those on humans, the effects of oxytocin on dogs' social behavior are not universally positive but are constrained by individual characteristics and the context. Nevertheless, oxytocin administration has the potential to improve the social behavior of laboratory beagle dogs that are socially less proficient when interacting with humans, which could have both applied and animal welfare implications.
... We see the advent of the era when high quality video and sound recording became possible with the extremely widespread handheld devices for basically everyone, and large files can be easily transmitted through the internet. Consequently, amateurs can be involved in increasingly sophisticated and interactive research protocols, where they can be instructed by the researchers how and what to do while conducting experiments with, for example, their companion animals at home (Laverack et al., 2021;Smith et al., 2021). ...
... Among these, Tiira (2021) used a citizen science approach to test a novel device to combat separation anxiety in dogs. Smith et al. (2021) brought us their widely applauded study on cats' performance in the so-called illusory contour susceptibility paradigm. This paper was downloaded over 26,000 times since its publication in July 2021. ...
Multiple species of animal are known to display different behaviours and have varying degrees of problem-solving task success when faced with transparent, semi-transparent or opaque versions of the same task. As such, transparency can affect how researchers interpret the limits of a species’ cognitive abilities or success on a task. We assessed how transparency may affect task engagement and social behaviours using the unsolvable task paradigm in domestic cats and their owners. We carried out a citizen science study that required cats to push over a non-magnetised (solvable) and magnetised (unsolvable) cup to reach an obscured food treat. All cats saw a transparent and opaque version of this cup. We assessed the effects of transparency and solvability on owner-directed and apparatus-directed behaviour displayed by the cat. We found significant differences in owner- and apparatus-directed gazing, as well as apparatus-directed touches, between transparent and opaque conditions. We also found an interaction effect between transparency and solvability for proximity with the owner, with cats being in proximity for longer durations with the owner in solvable, transparent conditions. No main effects of solvability were found on any recorded owner- or apparatus-directed behaviour. We discuss the implications of transparency on unsolvable task engagement, as well as the implementation of citizen science methods, particularly in cat research.
The dog is a so far unique species to study interspecific communication and a promising evolutionary model for preverbal human communication. Recently cats were reported to show some similar skills to dogs. Here we directly compared both the testability and the success of companion dogs and cats in relying on human distal pointing gestures. Due to differences in their domestication, social and ecological background, and developmental processes, we expected better performance from dogs compared to cats. Using an object-choice task, cats made considerably fewer choices than dogs in the laboratory environment, and their tendency to make a choice declined during trials. They were slightly more testable at home, where their willingness to choose did not decrease over time. Dogs made more successful choices than cats, both at the group and individual level, irrespective of the type of the pointing gesture. Older cats were more successful. Despite the two species’ rather similar role nowadays as human companions, our results support previous findings suggesting that, compared to the dog, the cat is a less ideal model to study some human communicative abilities in a laboratory environment.
A single invisible displacement object permanence task was administered to 19 cats (Felis catus). In this task, cats watched a target object from behind a transparent panel. However, cats had to walk around an opaque panel to reach the object. While cats were behind the opaque panel, the object was hidden behind one of two screens. As cats did not perceive the disappearance of the object behind the target screen, the object was invisibly hidden. Results showed that cats solved this task with great flexibility, which markedly contrasts with what has been observed in previous research. The discussion emphasizes the difference between the typical Piagetian task in which the information necessary to succeed must be dealt with in retrospective way, whereas in our task cats had to anticipate a new position of the object. The ecological relevance of this new task is also discussed.
Investigating perceptual and cognitive abilities of zoo animals might help to improve their husbandry and enrich their daily life with new stimuli. Developing new environmental enrichment programs and devices is hence necessary to promote species-specific behaviors that need to be maintained in controlled environments. As far as we are aware, no study has ever tested the potential benefits of motion illusions as visual enrichment for zoo animals. Starting from a recent study showing that domestic cats are spontaneously attracted by a well-known motion illusion, the Rotating Snake (RS) illusion, we studied whether this illusion could be used as a visual enrichment for big cats. We observed the spontaneous behavior of three lionesses when three different visual stimuli were placed in their environment: the RS illusion and two control stimuli. The study involved two different periods: the baseline and the RS period, in which the visual stimuli were provided to the lionesses. To assess whether the lionesses were specifically attracted by the RS illusion, we collected data on the number of interactions with the stimuli, as well as on the total time spent interacting with them. To investigate the effect of the illusion on the animals’ welfare, individual and social behaviors were studied, and compared between the two periods. The results showed that two lionesses out of three interacted more with the RS stimulus than with the two control stimuli. The fact that the lionesses seemed to be more inclined to interact with the RS stimulus indirectly suggests the intriguing possibility that they were attracted by the illusory motion. Moreover, behavioral changes between the two periods were reported for one of the lionesses, highlighting a reduction in self-directed behaviors and an increase in attentive behaviors, and suggesting positive welfare implications. Thus, behavioral observations made before and during the presentation of the stimuli showed that our visual enrichment actually provided positive effects in lionesses. These results call for the development of future studies on the use of visual illusions in the enrichment programs of zoo animals.
Boundary completion is one of the desired properties of a robust object boundary detection model, since in real-word images the object boundaries are commonly not fully and clearly seen. An extreme example of boundary completion occurs in images with illusory contours, where the visual system completes boundaries in locations without intensity gradient. Most illusory contour models extract special image features, such as L and T junctions, while the task is known to be a difficult issue in real-world images. The proposed model uses a functional optimization approach, in which a cost value is assigned to any boundary arrangement to find the arrangement with minimal cost. The functional accounts for basic object properties, such as alignment with the image, object boundary continuity, and boundary simplicity. The encoding of these properties in the functional does not require special features extraction, since the alignment with the image only requires extraction of the image edges. The boundary arrangement is represented by a border ownership map, holding object boundary segments in discrete locations and directions. The model finds multiple possible image interpretations, which are ranked according to the probability that they are supposed to be perceived. This is achieved by using a novel approach to represent the different image interpretations by multiple functional local minima. The model is successfully applied to objects with real and illusory contours. In the case of Kanizsa illusion the model predicts both illusory and real (pacman) image interpretations. The model is a proof of concept and is currently restricted to synthetic gray-scale images with solid regions.
Due to the composition of the cone photoreceptors in the retina of dogs, it has been proposed they might demonstrate human-like red/green colour blindness. However, some assessments have shown that dogs may still be able to distinguish between red and green. This suggests that dogs may be differentiating between the two colours on the basis of their brightness. To further explore this issue, the present investigation tested dogs’ abilities to differentiate between two colours at different physical luminance levels. Seven dogs were trained on a simultaneous size discrimination task in which two circles were presented on a monitor. The colours of the circles were then varied such that dogs would choose one stimulus if they could discriminate between two colours and a different stimulus if they could not. Four experiments were conducted. The first presented dogs with yellow, blue, green, and red stimuli at their maximum red, green, and blue (RGB) values. All seven dogs were equally proficient at discriminating between red and green, yellow and blue, and black and white stimuli as no difference in performance was observed (p = 0.52). In Experiments 2–4, the four colours were presented with equal physical luminance across three different intensities. All seven dogs successfully discriminated between all four colours when the colours were isoluminant at 34.6 cd/m² as no differences in performance was observed (p = 0.10). When presented with isoluminant stimuli at 41.9 cd/m², a difference was observed between conditions, with the dogs failing to detect red stimuli presented on a green background compared to the achromatic controls (p = 0.03). When presented with stimuli at 49.3 cd/m², a difference was again observed between conditions, but this time the dogs were unable to detect blue stimuli presented on a yellow background compared to the achromatic controls (p < 0.01). These findings demonstrate that luminance levels of stimuli can affect colour discrimination and what dogs are able to see on computer screens. These results have important implications in how cognition is studied in dogs through the use of presenting stimuli on monitors.
The comparative study of the perception of visual illusions between different species is increasingly recognized as a useful noninvasive tool to better understand visual perception and its underlying mechanisms and evolution. The aim of the present study was to test whether the domestic cat is susceptible to the Delboeuf illusion in a manner similar to other mammalian species studied to date. For comparative reasons, we followed the methods used to test other mammals in which the animals were tested in a 2-way choice task between same-size food stimuli presented on different-size plates. In 2 different control conditions, overall the 18 cats tested spontaneously chose more often the larger amount of food, although at the individual level, they showed interindividual differences. In the Delboeuf illusion condition, where 2 equal amounts of food were presented on different-size plates, all cats chose the food presented on the smaller plate more often than on the larger one, suggesting that they were susceptible to the illusion at the group level, although at the individual level none of them performed significantly above chance. As we found no correlation between the cats’ overall performance in the control conditions and their performance in the illusion condition, we propose that the mechanisms underlying spontaneous size discrimination and illusion perception might be different. In the discussion, we compare the results of the present study with the results for other previously tested mammals and highlight some possible reasons for their similarities and differences.
Domestic cats (Felis catus) are popular pets worldwide and play an important role in the lives of many of their owners; however, there is growing awareness of the potential negative impacts of cats. Accordingly, there is increasing interest in pet cat management, including changing the attitudes and behaviours of cat owners. The Cat Tracker citizen science project was conducted in South Australia to better understand domestic cats, their movement, and related community views. The project was deliberately designed to engage cat owners and assist them to make informed decisions about the management of their pet cats. The project collected data through an online social survey (n = 3192) and GPS tracking of pet cats (n = 428), conducted between February 2015 and September 2016. A public report was published in February 2017 and an evaluation survey (n = 410) was conducted between March and May 2017. This study evaluates the project and examines its impact on participant knowledge, attitude, and behaviour. We found that participation in the tracking activity had a statistically significant influence on participant-reported learning. For participant cat owners, we recorded statistically significant increases in the level of importance placed on containing cats (both during the day and at night). Participants reported that they changed their behaviour with existing pet cats and reported intentions to change behaviour with future pet cats. We discuss impacts beyond what we set out to measure, including impacts on project onlookers, profound impacts on participants, and how the rebound effect (which can generate negative impacts) may be avoided. We describe social science applied to citizen science and advocate for further research in this area to understand how projects can drive positive changes in knowledge, attitudes, and behaviours.
Susceptibility to geometrical visual illusions has been tested in a number of non-human animal species, providing important information about how these species perceive their environment. Considering their active role in human lives, visual illusion susceptibility was tested in domestic dogs (Canis familiaris). Using a two-choice simultaneous discrimination paradigm, eight dogs were trained to indicate which of two presented circles appeared largest. These circles were then embedded in three different illusory displays; a classical display of the Ebbinghaus–Titchener illusion; an illusory contour version of the Ebbinghaus–Titchener illusion; and the classical display of the Delboeuf illusion. Significant results were observed in both the classical and illusory contour versions of the Ebbinghaus–Titchener illusion, but not the Delboeuf illusion. However, this susceptibility was reversed from what is typically seen in humans and most mammals. Dogs consistently indicated that the target circle typically appearing larger in humans appeared smaller to them, and that the target circle typically appearing smaller in humans, appeared larger to them. We speculate that these results are best explained by assimilation theory rather than other visual cognitive theories explaining susceptibility to this illusion in humans. In this context, we argue that our findings appear to reflect higher-order conceptual processing in dogs that cannot be explained by accounts restricted to low-level mechanisms of early visual processing.
In humans, geometrical illusions are thought to reflect mechanisms that are usually helpful for seeing the world in a predictable manner. These mechanisms deceive us given the right set of circumstances, correcting visual input where a correction is not necessary. Investigations of non-human animals’ susceptibility to geometrical illusions have yielded contradictory results, suggesting that the underlying mechanisms with which animals see the world may differ across species. In this review, we first collate studies showing that different species are susceptible to specific illusions in the same or reverse direction as humans. Based on a careful assessment of these findings, we then propose several ecological and anatomical factors that may affect how a species perceives illusory stimuli. We also consider the usefulness of this information for determining whether sight in different species might be more similar to human sight, being influenced by contextual information, or to how machines process and transmit information as programmed. Future testing in animals could provide new theoretical insights by focusing on establishing dissociations between stimuli that may or may not alter perception in a particular species. This information could improve our understanding of the mechanisms behind illusions, but also provide insight into how sight is subjectively experienced by different animals, and the degree to which vision is innate versus acquired, which is difficult to examine in humans.
Family dogs and dog owners offer a potentially powerful way to conduct citizen science to answer questions about animal behavior that are difficult to answer with more conventional approaches. Here we evaluate the quality of the first data on dog cognition collected by citizen scientists using the Dognition.com website. We conducted analyses to understand if data generated by over 500 citizen scientists replicates internally and in comparison to previously published findings. Half of participants participated for free while the other half paid for access. The website provided each participant a temperament questionnaire and instructions on how to conduct a series of ten cognitive tests. Participation required internet access, a dog and some common household items. Participants could record their responses on any PC, tablet or smartphone from anywhere in the world and data were retained on servers. Results from citizen scientists and their dogs replicated a number of previously described phenomena from conventional lab-based research. There was little evidence that citizen scientists manipulated their results. To illustrate the potential uses of relatively large samples of citizen science data, we then used factor analysis to examine individual differences across the cognitive tasks. The data were best explained by multiple factors in support of the hypothesis that nonhumans, including dogs, can evolve multiple cognitive domains that vary independently. This analysis suggests that in the future, citizen scientists will generate useful datasets that test hypotheses and answer questions as a complement to conventional laboratory techniques used to study dog psychology.
We
present the first evidence that cats experience visual illusions and that a
non-human animal can see illusory motion. In three videos we show cats reacting
with hunting behavior when watching the Rotating Snakes illusion. This is taken
to mean that cats see illusory motion in this image due to the propensity of
cats to pursue movement. This is further supported by a survey where 29% of the
respondents answered that their cat reacted to the illusion. A number of
preferential looking experiments were also indicative of cats experiencing the
illusion, but not conclusively so.
In 1909, Abbott Thayer suggested that the study of animal coloration lies in the domain of artists because it deals with optical illusions. He proposed, for example, that prey color patterns may obliterate the animal's outline to make the wearer appear invisible to its preda-tors. Despite a long history of research on the neuropsychology of visual illusions in humans, the question of whether they can occur in other animals has remained largely neglected. In this review, we first examine whether the visual effects generated by an animal's shape, coloration, movement, social environment, or direct manipulation of the environment might distort the receiver's perspective to form an illusion. We also consider how illusions fit into the wider conceptual framework of sensory perception and receiver psychol-ogy, in order to understand the potential significance of these (and other) visual effects in animal communication. Secondly, we con-sider traits that manipulate visual processing tasks to intimidate or mislead the viewer. In the third part of the review, we consider the more extreme cases of sensory manipulation, in which individuals or their traits disrupt, overstimulate, or inactivate receivers' sensory systems. Although illusions present just one form of sensory manipulation, we suggest that they are likely to be more common than previously suspected. Furthermore, we expect that research in this area of sensory processing will provide significant insights into the cognitive psychology of animal communication.
Bamboo sharks (Chiloscyllium griseum) were tested for their ability to perceive subjective and illusionary contours as well as line length illusions. Individuals were first trained to differentiate between squares, triangles, and rhomboids in a series of two alternative forced-choice experiments. Transfer tests then elucidated whether Kanizsa squares and triangles, grating gaps and phase shifted abutting gratings were also perceived and distinguished. The visual systems of most vertebrates and even invertebrates perceive illusionary contours despite the absence of physical luminance, color or textural differences. Sharks are no exception to the rule; all tasks were successfully mastered within 3-24 training sessions, with sharks discriminating between various sets of Kanizsa figures and alternative stimuli, as well as between subjective contours in >75% of all tests. However, in contrast to Kanizsa figures and subjective contours, sharks were not deceived by Müller-Lyer (ML) illusions. Here, two center lines of equal length are comparatively set between two arrowheads or -tails, in which case the line featuring the two arrow tails appears to be longer to most humans, primates and birds. In preparation for this experiment, lines of varying length, and lines of unequal length randomly featuring either two arrowheads or -tails on their ends, were presented first. Both sets of lines were successfully distinguished by most sharks. However, during presentation of the ML illusions sharks failed to succeed and succumbed either to side preferences or chose according to chance.
The human visual system sees an illusory contour where there is a fault line across a regular striped pattern. We demonstrate that bees respond as if they see the same illusory contour. There is also a type of neuron in the lobula of the dragonfly optic lobe which responds directionally to motion of the illusory contour as if to an edge or line. Apparently insects have a mechanism that sees illusory contours and therefore assists in the demarcation of edges and objects at places where local contrast falls to zero at an edge, or where one textured object partially obscures another. These results suggest that insect vision, although spatially crude and low in processing power, sees separate objects by similar mechanisms to our own.
Subjects were 384 Moroccan males (age range 6–22 yrs.), divided into 16 equal groups, according to the factorial design: age (4) x schooling (2) x environment (2). Subjects were tested on four Ponzo configurations (differing in contextual information) from Leibowitz eta/. (1969), the Ponzo perspective stimulus from Segall et al. (1966), the CEFT from Witkin et at. (1971), and a measure of pictorial depth perception. Individual measures of contact with mass-media and urban life were collected on each subject. Analyses indicated that all main factors of age, schooling, and environment played important, and differing, roles in inducing illusion susceptibility. Piaget's (1969) theory of primary and secondary illusions was found useful in understanding the results of the Ponzo configurations used in the study. Primary illusion configurations were found to be relatively insensitive to experiential variables, and illusion susceptibility decreased with chronological age. In contrast, secondary illusion configurations were affected by many experiential factors, and illusion susceptibility was mediated through perceptual development and pictorial depth perception rather than chronological age. It was concluded that single-factor theories of ontogenetic change in illusion susceptibility were inadequate to explain the complex interactions found in this studyr
This study investigates the effect of hiding enrichment on stress and behaviour of kennelled cats. Forty-three cats were studied either with a BC SPCA Hide & Perch™ box as enrichment, or with an open bed as control. Observations consisted of Stress Score, approach test and scan sample, recorded daily over the five days following a cat's entrance into the adoption centre, and again on the 14th day if the cat was still present. Days until adoption was noted for cats adopted during the study period. A survey was given to adopters of study cats in an attempt to determine the motivations underlying their choice of cat.
A significant reduction in stress was noted between all study days in the enriched group. Stress levels in this group declined further between the fifth and the 14th day, while those of the control group increased. Cats in the enriched group were significantly more likely to approach and displayed relaxed behaviours much more frequently. No significant difference was found between the two groups in days until adoption, percentage adopted, or in the reasons provided by the new owners in the adoption survey; however temperament was found to be the highest ranked reason for choosing a cat from either group.
Results of this study suggest that the welfare of kennelled cats is greatly improved if they are provided with the opportunity to perform effective hiding behaviour, and that the ability to perform such a behaviour does not decrease the likelihood of those cats being adopted.
As adult cats can often be difficult to re-home, they may spend long periods in rescue shelters where barren housing and inconsis-tent handling can reduce their welfare. In this study, 165 adult cats in an animal shelter in Vancouver, Canada, were assigned to four treatments. The Basic Single treatment reflected typical conditions in that particular shelter, with cats handled in an inconsistent manner by various staff and housed singly in relatively barren cages. Three alternative treatments involved more consistent, positive handling by only the experimenter and research assistants, plus three housing conditions: Enriched Single (individual cages with oppor-tunities to perch and hide), Basic Communal (group housing with opportunity for each cat to have personal space), and Enriched Communal (group housing enriched to encourage play and cat – cat interaction). The Basic Single treatment had the lowest percentage adopted in 21 days (45% versus 69-76% for other treatment, and higher stress scores than other treatments. The three alternative treatments did not differ significantly on any measure. Cats euthanised for poor health showed higher stress levels when alive than other cats. In a questionnaire, most adopters cited certain behavioural/emotional traits ('friendly', 'playful', 'happy') as reasons for selecting cats; these were generally associated with lower stress scores. The results suggest that consistent handling combined with a range of improved housing options can improve the chances of adoption for adult cats, perhaps by reducing fear-related behaviours that make cats less attractive to adopters.
This paper reports a cross-cultural investigation of susceptibility to geometrical illusions based upon student samples in
Ghana and Scotland. The results indicate that: (1)cultural differences in susceptibility to illusions can be found among Ss
exposed to lengthy formal education of a similar type; (2) the perceptual consequences of professional training in art and
architecture tend to be moderate within a culture; but (3) the combined outcome of training across cultures tends to reduce
cultural differences in susceptibility to illusions. They also raise a problem concerning the supposed positive relationship
between field dependence and susceptibility to illusions. Some implications of these results are considered.
The processing of Kanizsa-square illusory figures was studied in two experiments with four humans and two chimpanzees. Subjects
of the two species were initially trained to select a Kanizsa-square illusory figure presented in a computerized two-alternative
forced choice task. After training, adding narrow closing segments to the pacman inducers that composed the Kanisza illusory
figures lowered performance in both chimpanzees and humans, suggesting that the discrimination could be controlled by the
perception of illusory forms. A second experiment assessed transfer of performance with five sets of figures in which the
size of the inducers and their separation were manipulated. Only for chimpanzees was performance directly controlled by separation,
suggesting that chimpanzees are more sensitive than humans to the separation between visual elements.
IN a normal cat, neurones of the visual cortex are selective for the orientation of lines and edges in the visual field, and the preferred orientations of different cells are distributed all around the clock1. Hirsch and Spinelli2 have recently reported that early visual experience can change this organization. They reared kittens with one eye viewing vertical stripes, the other horizontal, and found that out of twenty-one neurones with elongated receptive fields all were monocularly driven, and in all but one case the orientation of the receptive field closely matched the pattern experienced by that eye.
The present study examined whether color spreading and illusory contours in the neon color spreading effect of Ehrenstein figures are governed by different mechanisms. In the experiment, Ehrenstein figures with colored crosses inserted in the central gaps were used. There were three luminance conditions: the luminance of the Ehrenstein figures was lower than, the same as, or higher than the luminance of the background. In each condition, 16 trials (2 sets of instructions X 8 repetitions) were conducted in a random order. Subjects were required to adjust the luminance of the colored crosses according to one of the two sets of instruction given before each trial. One was to adjust the upper and lower thresholds in the luminance of the colored crosses such that their color was seen to spread out of the crosses. The other was to adjust the thresholds such that circular illusory contours were visible. It was found that illusory contours disappeared and the color spreading remained when the crosses and the Ehrenstein figures were in or nearly in isoluminance or when the Ehrenstein figures and the background were in isoluminance. These results suggest that color spreading and illusory contours are governed by different mechanisms.
Robust form perception and underlying neuronal mechanisms require generalized representation of object boundaries, independent of how they are defined. One visual ability essential for form perception is reconstruction of contours absent from the retinal image. Here we show that barn owls perceive subjective contours defined by grating gaps and phase-shifted abutting gratings. Moreover, single-neuron recordings from visual forebrain (visual Wulst) of awake, behaving birds revealed a high proportion of neurons signaling such subjective contours, independent of local stimulus attributes. These data suggest that the visual Wulst is important in contour-based form perception and exhibits a functional complexity analogous to mammalian extrastriate cortex.
This review article illustrates that mammals, birds and insects are able to perceive illusory contours. Illusory contours lack a physical counterpart, but monkeys, cats, owls and bees perceive them as if they were real borders. In all of these species, a neural correlate for such perceptual completion phenomena has been described. The robustness of neuronal responses and the abundance of cells argue that such neurons might indeed represent a neural correlate for illusory contour perception. The internal state of an animal subject (i.e., alert and behaving) seems to be an important factor when correlating neural activity with perceptual phenomena. The fact that the neural network necessary for illusory contour perception has been found in relatively early visual brain areas in all tested animals suggests that bottom-up processing is largely sufficient to explain such perceptual abilities. However, recent findings in monkeys indicate that feedback loops within the visual system may provide additional modulation. The detection of illusory contours by independently evolved visual systems argues that processing of edges in the absence of contrast gradients reflects fundamental visual constraints and not just an artifact of visual processing.
The Ebbinghaus (Titchener) illusion was examined in a remote culture (Himba) with no words for geometric shapes. The illusion was experienced less strongly by Himba compared with English participants, leading to more accurate size contrast judgments in the Himba. The study included two conditions of inducing stimuli. The illusion was weaker when the inducing stimuli were dissimilar (diamonds) to the target (circle) compared with when they were similar (circles). However, the illusion was weakened to the same extent in both cultures. It is argued that the more accurate size judgments of the Himba derive from their tendency to prioritize the analysis of local details in visual processing of multiple objects, and not from their impoverished naming.
Domestic dogs play many vital roles in human lives; however, relatively little is known about how they perceive the world visually. Given dogs’ recent popularity as a subject in cognitive and behavioural studies, it is important to understand how they visually interpret the world around them. One way to evaluate perception is to assess illusion susceptibility; specifically, how visual information is processed, interpreted and modified post‐retinally. While illusion susceptibility has been used across a variety of species to comparatively assess the similarities and differences in visual processing and perception, this relatively novel methodological approach has only recently been adapted to evaluate perception in domestic dogs. Here, we present a comprehensive overview of the findings from studies that have evaluated domestic dogs’ illusion susceptibility, highlighting the relevance of these results for those studying illusion susceptibility in animals as well as canine behaviour and cognition. More specifically, the ultimate goal of this review is to answer the questions: (a) Are dogs susceptible to visual illusions? (b) If so, are they susceptible to illusions in a way that parallels humans and/or other animals? (c) Are findings, within dogs, consistent and if not, how might these be interpreted and explained?
The domestic cat (Felis silvestris catus) has shared an intertwined existence with humans for thousands of years, living on our city streets and in our homes. Yet, little scientific research has focused on the cognition of the domestic cat, especially in comparison with human's other companion, the domestic dog (Canis lupus familiaris). This review surveys the current status of several areas of cat cognition research including perception, object permanence, memory, physical causality, quantity and time discrimination, cats' sensitivity to human cues, vocal recognition and communication, attachment bonds, personality, and cognitive health. Although interest in cat cognition is growing, we still have a long way to go until we have an inclusive body of research on the subject. Therefore, this review also identifies areas where future research must be conducted. In addition to the scientific value of future work in this area, future research on cat cognition could have an important influence on the management and welfare of pet and free-roaming cats, leading to improved human-cat interactions.
Domestic cats are exposed to a variety of stressful stimuli, which may have a negative effect on the cats' welfare and trigger a number of behavioural changes. Some of the stressors most commonly encountered by cats include changes in environment, inter-cat conflict, a poor human-cat relationship and the cat's inability to perform highly motivated behaviour patterns. Stress is very likely to reduce feed intake, and stress-related anorexia may contribute to the development of potentially serious medical conditions. Stress also increases the risk of cats showing urine marking and some forms of aggression, including redirected aggression. A number of compulsive disorders such as over-grooming may also develop as a consequence of stressful environments. Some of the main strategies to prevent or reduce stress-related behavioural problems in cats are environmental enrichment, appropriate management techniques to introduce unfamiliar cats to each other and the use of the synthetic analogue of the feline facial pheromone. As the stress response in cats depends, to a large extent, on the temperament of the animal, breeding and husbandry strategies that contribute to the cat developing a well-balanced temperament are also very useful.
© The Author(s) 2015.
Sixteen domestic cats were used to investigate the pituitary-adrenal, pituitary-gonadal and behavioral consequences of an unpredictable handling and husbandry routine. After a 10-day baseline period of standard laboratory procedures, eight cats (‘stressed cats’, STR) were subjected to a 21-day period of altered caretaking characterized by irregular feeding and cleaning times, absence of talking and petting by humans, and daily unpredictable manipulations. Eight control cats (CON group) were maintained for 21 days on the standard caretaking schedule. Behavior was recorded on time-lapse video 24 h day−1, urine was collected daily for cortisol analyses, and hormone stimulation tests with synthetic adrenocorticotropic hormone (ACTH) and luteinizing hormone-releasing hormone (LHRH) were conducted before and after the 3-week treatment period. Results indicate that the STR cats were chronically stressed by the altered caretaking routine. Urinary cortisol concentrations were consistently elevated throughout the 3-week period, adrenal sensitivity to ACTH was enhanced and pituitary sensitivity to LHRH was reduced. Active exploratory and play behavior was suppressed, and STR cats spent more time awake/alert and attempting to hide. Hiding was negatively correlated with cortisol concentration and, therefore, may be an important behavior for coping with uncontrollable and unpredictable captive environments. These results indicate that qualitatively poor caretaking is a potent psychological stressor for confined cats that may eventually compromise reproduction through behavioral or physiological mechanisms. To promote well-being, caged cats should be provided with appropriate places for concealment.
Presents an introductory text on the 3 major areas of visual perception: sensory organization, information processing, and spatial organization. Major topics include theoretical and empirical evidence concerning the mechanisms for perceiving color, form, and movement. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Notes that normally the visual experience of a line or a margin corresponds to a jump or a sharp discontinuity in the intensity, wave length, or spectral composition of the radiation that stimulates 2 contiguous areas of the retina. It is not, however, difficult to create situations in which there is not such correspondence. That is, quite visible contours can appear in parts of the visual field where the stimulation is completely homogeneous. These contours without gradients have lately been diversely interpreted. In this article these interpretations are discussed, and some new observations are presented. (22 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
We report four experiments in which the strength ofedge-interpoiat-ion in illusory figure displays was tested. In Experiment
1, we investigated the relative contributions of the lengths of luminance-specified edges and the gaps between them to perceived
boundary clarity as measured by using a magnitude estimation procedure. The contributionaoLthese variables were found to be
best characterized by a ratio of the length of luminance-specified contour to the length of the entire edge (specified plus
interpolated edge). Experiment 2 showed that this ratio predicts boundary clarity for a wide range of ratio values and display
sizes.There was no evidence that illusory figure boundaries are clearer in displays with small gaps than they are in displays
with larger gaps and equivalent ratios. In Experiment 3, using a more sensitive pairwise comparison paradigm, we again found
no such effect. Implications for boundary interpolation in general, including perception of partially occluded objects, are
discussed. The dependence of interpolation on the ratio of physically specified edges to total edgelength has thedesirable
eeological consequence that unit formation will not change with variations in viewing distance.
Fourteen adult female domestic cats were watched by two observers for 3 months. Ratings of 18 aspects of each cat's behavioural style were obtained independently from each observer. Correlations between observers were statistically significant for 15 of the 18 aspects and seven of the correlation coefficients were greater than 0·7. The ratings were compared with results of direct recording methods, where equivalent measures were available and, in five out of six cases, the results of the ratings and direct methods were significantly correlated. The rating method is, therefore, generally reliable and can be adequately validated. Some assessments of observer ratings which are not obviously and easily related to direct recordings may prove particularly useful in developmental studies of alternative modes of behaviour and the origins of individual differences.
A new study has found that the tuning properties of neurons in the primary visual cortex of cats change as they learn an orientation-discrimination task, casting new light on the neuronal basis of perceptual learning.
Perceptual learning has been documented in adult humans over a wide range of tasks. Although the often-observed specificity of learning is generally interpreted as evidence for training-induced plasticity in early cortical areas, physiological evidence for training-induced changes in early visual cortical areas is modest, despite reports of learning-induced changes of cortical activities in fMRI studies. To reveal the physiological bases of perceptual learning, we combined psychophysical measurements with extracellular single-unit recording under anesthetized preparations and examined the effects of training in grating orientation identification on both perceptual and neuronal contrast sensitivity functions of cats.
We have found that training significantly improved perceptual contrast sensitivity of the cats to gratings with spatial frequencies near the "trained" spatial frequency, with stronger effects in the trained eye. Consistent with behavioral assessments, the mean contrast sensitivity of neurons recorded from V1 of the trained cats was significantly higher than that of neurons recorded from the untrained cats. Furthermore, in the trained cats, the contrast sensitivity of V1 neurons responding preferentially to stimuli presented via the trained eyes was significantly greater than that of neurons responding preferentially to stimuli presented via the "untrained" eyes. The effect was confined to the trained spatial frequencies. In both trained and untrained cats, the neuronal contrast sensitivity functions derived from the contrast sensitivity of the individual neurons were highly correlated with behaviorally determined perceptual contrast sensitivity functions.
We suggest that training-induced neuronal contrast gain in area V1 underlies behaviorally determined perceptual contrast sensitivity improvements.
The ability of fish to perceive subjective (or illusory) contours, ie contours that lack a physical counterpart in terms of luminance contrast gradients, was investigated. In the first experiment, redtail splitfins (Xenotoca eiseni), family Goodeidae, were trained to discriminate between a geometric figure (a triangle or a square) on various backgrounds and a background without any figure. Thereafter, the fish performed test trials in which illusory squares or triangles were obtained by (i) interruptions of a background of diagonal lines, (ii) phase-shifting of a background of diagonal lines, and (iii) pacmen spatially arranged to induce perception of Kanizsa subjective surfaces. In all three conditions, fish seemed to generalise their responses to stimuli perceived as subjective contours by humans. Fish chose, correctly, squares or triangles made of interrupted or phase-shifted diagonal lines from uniform backgrounds of diagonal lines, as well as illusory square or triangle Kanizsa figures from figures in which the inducing pacmen were scrambled. In the second experiment, fish were trained to discriminate between a vertical and a horizontal bar with luminance contrast gradients, and then tested with vertically and horizontally oriented illusory bars, created either through interruption or spatial phase-shift of inducing diagonal lines. Fish appeared to be able to generalise the orientation discrimination to illusory contours. These results demonstrate that redtail splitfins are capable of perceiving illusory contours.
We review the evolution of domestic animals, emphasizing the effect of the earliest steps of domestication on its course. Using the first domesticated species, the dog (Canis familiaris), for illustration, we describe the evolutionary peculiarities during the historical domestication, such as the high level and wide range of diversity. We suggest that the process of earliest domestication via unconscious and later conscious selection of human-defined behavioral traits may accelerate phenotypic variations. The review is based on the results of a long-term experiment designed to reproduce early mammalian domestication in the silver fox (Vulpes vulpes) selected for tameability or amenability to domestication. We describe changes in behavior, morphology and physiology that appeared in the fox during its selection for tameability, which were similar to those observed in the domestic dog. Based on the data of the fox experiment and survey of relevant data, we discuss the developmental, genetic and possible molecular genetic mechanisms underlying these changes. We ascribe the causative role in evolutionary transformation of domestic animals to the selection for behavior and to the neurospecific regulatory genes it affects.
Allowing very young kittens to see with only one eye at a time greatly reduces the proportion of binocular cortical cells.
Compared to normal cats these specially reared animals suffer deficits in binocular depth perception while retaining normal
activity in the two eyes. Evidently, binocular cells play a crucial role in stereopsis.
We present the first evidence that a non-human species (the cat) is able to discriminate the orientation of illusory contours. Following Vogels and Orban45, we used two types of illusory contours. In one type, the illusory contour was defined by a number of contour-inducing semicircles, of which the endpoints were separated by a gap. In the other pattern, the inducing semicircles were shifted in phase along their diameter and their endpoints were aligned along the contour. Just noticeable differences in orientation were measured (at the 73.5% correct level), using a Wetherill and Levitt49 staircase procedure. Values in the order of 11 degrees were obtained when using the first type of illusory contour. Just noticeable differences with the second type were in the order of 17 degrees. Reducing the salience of the illusory contour, whether by scrambling the contour, or by decreasing the number or the contrast of inducing semicircles, systematically increased discrimination thresholds.
Behavioural techniques were used to determine whether cats are able to see subjective contours. Through several stages of testing with increasingly complex displays, cats continued to respond to a figure defined by subjective contours. This result provides the first direct evidence that a nonhuman perceives subjective contours.
We investigated responses of neurones in cortical areas 17 and 18 and in the dorsal lateral geniculate nucleus (dLGN) of the cat to a phase shift in a moving line pattern forming a border without a luminance gradient ("subjective contour"). In both areas 17 and 18, S cells and B cells respond only slightly or not at all along the phase shift while C cells respond strongly. The response of C cells is strongest for line patterns with medium line separation and decreases with smaller and larger separation. In the dLGN the relative magnitude of neuronal responses along a phase shift is similar to that of C cells. However, C cells respond uniformly along the entire phase shift, whereas geniculate cells merely respond to individual line ends along the phase shift. In addition we compared responses along a phase shift and those to a luminance gradient formed by a dotted line whose dots were separated by the same distance as the line ends along the phase shift. S cells and B cells respond preferentially to dotted lines whereas C cells and geniculate cells respond equally well along both phase shifts and dotted lines. Possible explanations for these results in terms of receptive field structure and differences in inhibitory input to the cells are discussed. Differential neurone responses may account for the perceptual distinctness of the contours with and without luminance gradients.
Two separate traditions of research into the Müller-Lyer illusion have existed for at least 70 years: the ecological and the developmental. To assess the ecological hypothesis, a sufficient range in visual ecology typically has been sought in cross-cultural comparisons; however, many of these comparisons have been inconclusive, especially when other ethnic variables have been held constant. These insignificant findings are considered to result from a confounding of the ecological and developmental variables. Appropriate sampling from Temne and Eskimo populations (enabling, in turn, one variable to be matched while the other is varied) demonstrates this confounding within cultures and, when eliminated, the significant influence of each variable on susceptibility to the Müller-Lyer illusion. Further work, however, is needed to discover other factors which will account for variance in susceptibility between cultures.
The question of whether phenomena of human perception such as amodal completion are also present in visual perception in the mouse was investigated. Three experiments based on a simultaneous-discrimination task were carried out with the aid of a jumping-stand similar to the one used by Lashley. The subjects were 36 male mice (DBA/J); 12 took part in each experiment. After reaching the learning criterion (87% correct responses), the mice performed 15 test trials which were interpolated between the learning trials. The test trials were constructed so as to allow the observation of any perceptual phenomena similar to amodal perception. Of the 36 subjects, 23 reached the criterion necessary to access the test phase. A significant number of them (17 out of 23, chi 2 = 5.261, p = 0.021) adopted a decisional strategy that seemed to indicate the occurrence of phenomena similar to amodal completion, and a trend in the same direction was observed in the performance of the other 6 subjects. The results allow the conclusion that a perceptual phenomenon which is similar to amodal completion in humans is present even at this phylogenetic level. Alternative interpretations are discussed.
Data obtained by the author and his colleagues on deficits in learning in cats reared in the lab breeding colony are reviewed. As compared with cats who lived free in a farm during the first 3-4 months of life, the lab-reared cats showed a dramatic impairment of delayed response learning to visual and auditory stimuli. They also showed some impairment of visual discrimination learning: they commited more errors than farm-reared cats when a discrimination apparatus had a partition between the stimuli, their reaction times were longer, and after lesions of the superior colliculus-pretectum complex their relearning was impaired. Thus, even moderate impoverishment of environment can considerably affect later learning ability.
A neural network model is developed to explain how visual thalamocortical interactions give rise to boundary percepts such as illusory contours and surface percepts such as filled-in brightnesses. Top-down feedback interactions are needed in addition to bottom-up feed-forward interactions to simulate these data. One feedback loop is modeled between lateral geniculate nucleus (LGN) and cortical area V1, and another within cortical areas V1 and V2. The first feedback loop realizes a matching process which enhances LGN cell activities that are consistent with those of active cortical cells, and suppresses LGN activities that are not. This corticogeniculate feedback, being endstopped and oriented, also enhances LGN ON cell activations at the ends of thin dark lines, thereby leading to enhanced cortical brightness percepts when the lines group into closed illusory contours. The second feedback loop generates boundary representations, including illusory contours, that coherently bind distributed cortical features together. Brightness percepts form within the surface representations through a diffusive filling-in process that is contained by resistive gating signals from the boundary representations. The model is used to simulate illusory contours and surface brightness induced by Ehrenstein disks, Kanizsa squares, Glass patterns, and café wall patterns in single contrast, reverse contrast, and mixed contrast configurations. These examples illustrate how boundary and surface mechanisms can generate percepts that are highly context-sensitive, including how illusory contours can be amodally recognized without being seen, how model simple cells in V1 respond preferentially to luminance discontinuities using inputs from both LGN ON and OFF cells, how model bipole cells in V2 with two colinear receptive fields can help to complete curved illusory contours, how short-range simple cell groupings and long-range bipole cell groupings can sometimes generate different outcomes, and how model double-opponent, filling-in and boundary segmentation mechanisms in V4 interact to generate surface brightness percepts in which filling-in of enhanced brightness and darkness can occur before the net brightness distribution is computed by double-opponent interactions.
Visual perception of objects depends on segmentation and grouping processes that act on fragmentary input. This paper gives a brief overview of these processes. A simple geometry accounting for contour interpolation is described, and its applications to 2D, 3D, and spatiotemporal object interpolation processes are considered. A method is described for distinguishing interpolation based on this geometry from more global or top-down influences. Results suggest a separation between interpolation based on relatively local stimulus relations, which give rise to precise boundary representations, and processes involving recognition from partial information, which do not. Aspects of the model-especially the unified treatment of illusory and occluded objects-raise questions about the nature of seeing. Although it is often believed that illusory objects are perceived, while occluded objects are inferred, I suggest that both research and theory converge in supporting a more unified account. Illusory and occluded contours and surfaces do not divide into the real, the perceived, and the inferred, but are all represented, and in key respects, derive from identical perceptual processes.
We used a preferential looking technique to investigate the effect of support ratio (a ratio of the physically specified contours to the total edge length) on the perception of Kanizsa illusory contours in infants aged 3-8 months. Previous work has shown that for adult observers the illusory-contour strength increases proportionally with the support ratio. When the support ratio was relatively high (66%), infants preferred illusory contours to non-illusory figures by 3-4 months of age (experiment 1). In contrast, only infants 7-8 months old showed this preference for illusory contours when the support ratio was reduced to 37% (experiment 3). Further, infants showed no preference for an outline version of the illusory-contour figure, which produced no illusory contours (experiment 2). This result confirms that the infants' preference reflects their perception of illusory contours. Our results show that (i) illusory-contour perception emerges at around 3-4 months of age, but (ii) that this ability is very limited until around 7-8 months of age.
Three classes of perceptual phenomena have repeatedly been associated with autism spectrum disorder (ASD): superior processing of fine detail (local structure), either inferior processing of overall/global structure or an ability to ignore disruptive global/contextual information, and impaired motion perception. This review evaluates the quality of the evidence bearing on these three phenomena. We argue that while superior local processing has been robustly demonstrated, conclusions about global processing cannot be definitively drawn from the experiments to date, which have generally not precluded observers using more local cues. Perception of moving stimuli is impaired in ASD, but explanations in terms of magnocellular/dorsal deficits do not appear to be sufficient. We suggest that abnormalities in the superior temporal sulcus (STS) may provide a neural basis for the range of motion-processing deficits observed in ASD, including biological motion perception. Such an explanation may also provide a link between perceptual abnormalities and specific deficits in social cognition associated with autism.