Motion parallax via head movements modulates visuo-motor control in pigeons.

Although it has been proposed that birds acquire visual depth cues through dynamic head movements, behavioral evidence on how birds use motion parallax depth cues caused by self-motion is lacking. This study investigated whether self-generated motion parallax modulates pecking motor control and visual size perception in pigeons (Columba livia). We trained pigeons to peck a target on a touch monitor and to classify it as small or large. To manipulate motion parallax of the target, we changed the target position on the monitor according to the bird's head position in real time using a custom-built head tracker with two cameras. Pecking motor control was affected by the manipulation of motion parallax: when the motion parallax signified the target position farther than the monitor surface, the head position just before pecking to target was near the monitor surface, and vice versa. By contrast, motion parallax did not affect how the pigeons classified target sizes, implying that motion parallax might not contribute to size constancy in pigeons. These results indicate that motion parallax via head movements modulates pecking motor control in pigeons, suggesting that head movements of pigeons have the visual function of accessing motion parallax depth cues.

Dogs and cats prioritize human action: choosing a now-empty instead of a still-baited container.

Dogs and cats are sensitive to human social signals such as pointing, gazing and facial expressions. Previous studies have demonstrated that dogs show over-reliance on human actions in the presence of conflicting physical cues. However, it is still unclear whether this tendency is specific to dogs, or shared with other domesticated animals. Here, we compared the behavior of dogs and cats in a two-choice task after they saw a person taking and pretending to eat food from a baited container. After one experimenter showed the dogs (Experiment 1) or cats (Experiment 2) two opaque containers, each containing a piece of the food, another (the demonstrator) removed food from one container and ate it (Eating condition), or simply picked up the food and returned it to the container (Showing condition). We recorded which container the subjects approached first after the demonstration. Both dogs and cats were less likely to choose the container associated with the human in the Eating than the Showing condition, although choice for this container was above chance in both conditions. In Experiment 3, we confirmed that dogs and cats naturally chose a baited over an empty container. These results suggest that both species' reasoning abilities might be influenced by a bias for prioritizing specific human actions. Although dogs and cats have different domestication histories, their social awareness of humans appears similar, possibly because they both share their environment with humans.

Pigeons (Columba livia) integrate visual motion using the vector average rule: effect of viewing distance.

Integrating local motion signals detected by the primary motion detector is crucial for representing a rigid, two-dimensional motion. The nature of motion integration has been studied using stimuli consisting of two superimposed sinusoidal gratings of different orientations, called plaid motion, and it has been shown that humans perceive integrated motion in the direction where the component constraint lines are intersected. We previously found that pigeons and humans perceive different movement directions from plaid motion; pigeons responded to the vector average direction of the gratings. Although this suggests that the underlying processes of motion integration differ between the two species, the viewing distance in the pigeon experiment, which used a touch panel procedure, was much smaller than in typical human experiments. The current study investigated the potential effect of viewing distance on the perception of plaid motion in pigeons. We trained six pigeons to detect whether motion directions were tilted leftward or rightward while a visual display was presented 0 or 40 cm from an operant chamber. The pigeons responded to plaid stimuli for both viewing distance conditions as if they perceived motion in the vector average direction of two-component gratings. The result indicates that the species difference in plaid perception is not an artefact of viewing distance and suggests that pigeons use a different strategy than humans for integrating visual motion.

Cats match voice and face: cross-modal representation of humans in cats (Felis catus).

We examined whether cats have a cross-modal representation of humans, using a cross-modal expectancy violation paradigm originally used with dogs by Adachi et al. (Anim Cogn 10:17-21, 2007). We compared cats living in houses and in cat cafés to assess the potential effect of postnatal experience. Cats were presented with the face of either their owner or a stranger on a laptop monitor after playing back the voice of one of two people calling the subject's name. In half of the trials the voice and face were of the same person (congruent condition) whereas in the other half of trials the stimuli did not match (incongruent condition). The café cats paid attention to the monitor longer in incongruent than congruent conditions, showing an expectancy violation. By contrast, house cats showed no similar tendency. These results show that at least café cats can predict their owner's face upon hearing the owner's voice, suggesting possession of cross-modal representation of at least one human. There may be a minimal kind or amount of postnatal experiences that lead to formation of a cross-modal representation of a specific person.

Pigeons (Columba livia) know when they will need hints: prospective metacognition for reference memory?

Despite their impressive cognitive abilities, avian species have shown less evidence for metacognition than mammals. We suspect that commonly used tasks such as matching to sample might be too demanding to allow metacognitive processing within birds' working memory. Here, we examined whether pigeons could control their behavior as a function of knowledge levels on a three-item sequence learning task, a reference memory task supposedly requiring fewer working memory resources. The experiment used two types of lists differing in familiarity. One was familiar to the pigeons through repeated exposure, whereas the other was novel in every new session. In test sessions, pigeons could choose between a trial with a hint specifying the next item to peck and one with no hint. However, successful responses in trials with a hint resulted in lowered rates of primary reinforcement: .60 in the first test and .75 in the second. Results showed that two of four pigeons chose the trial with a hint significantly more often before receiving a novel list than the familiar list in the four sessions of the first test, and three did so in the second test. Impressively, one bird showed robust evidence in the very first sessions in both tests. These results suggest that pigeons may monitor their long-term knowledge states and thereby control their environment before starting to solve a task.

The evolution of self-control.

Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.

Evaluation of third-party reciprocity by squirrel monkeys (Saimiri sciureus) and the question of mechanisms.

Social evaluation during third-party interactions emerges early in human ontogeny, and it has been shown in adult capuchin monkeys who witness violations of reciprocity in object exchanges: Monkeys were less inclined to accept food from humans who refused to reciprocate with another human. A recent study reporting similar evidence in marmoset monkeys raised the possibility that such evaluations might be based on species' inherent cooperativeness. We tested a species not renowned for cooperativeness-squirrel monkeys-using the procedure used with marmosets and found a similar result. This finding rules out any crucial role for cooperative tendencies in monkeys' responses to unfair exchanges. We then tested squirrel monkeys using procedures more similar to those used in the original study with capuchins. Squirrel monkeys again accepted food less frequently from non-reciprocators, but unlike capuchins, they also strongly preferred reciprocators. We conclude that neither squirrel monkeys nor marmoset monkeys engaged in emotional bookkeeping of the type that probably underlies social evaluation in capuchin monkeys; instead, they employed one or more simple behavioral rules. Further comparative studies are required to clarify the mechanisms underlying social evaluation processes across species.

There's no ball without noise: cats' prediction of an object from noise.

We used an expectancy violation procedure to ask whether cats could use a causal rule to infer the presence of an unseen object on hearing the noise it made inside a container and predict its appearance when the container was turned over. We presented cats with either an object dropping out of an opaque container or no object dropping out (turning-over phase) after producing either a rattling sound by shaking the container with the object inside, or no sound (shaking phase). The cats were then allowed to freely explore the experimental environment (exploration phase). The relation between the sound and the object matched with physical laws in half of the trials (congruent condition) and mismatched in the other half (incongruent condition). Inferring the presence of an unseen object from the noise was predicted to result in longer looking time in the incongruent condition. The prediction was supported by the cats' behavior during the turning-over phase. The results suggest that cats used a causal-logical understanding of auditory stimuli to predict the appearance of invisible objects. The ecology of cats' natural hunting style may favor the ability for inference on the basis of sounds.

Do dogs follow behavioral cues from an unreliable human?

Dogs are known to consistently follow human pointing gestures. In this study, we asked whether dogs "automatically" do this or whether they flexibly adjust their behavior depending upon the reliability of the pointer, demonstrated in an immediately preceding event. We tested pet dogs in a version of the object choice task in which a piece of food was hidden in one of the two containers. In Experiment 1, Phase 1, an experimenter pointed at the baited container; the second container was empty. In Phase 2, after showing the contents of both containers to the dogs, the experimenter pointed at the empty container. In Phase 3, the procedure was exactly as in Phase 1. We compared the dogs' responses to the experimenter's pointing gestures in Phases 1 and 3. Most dogs followed pointing in Phase 1, but many fewer did so in Phase 3. In Experiment 2, dogs followed a new experimenter's pointing in Phase 3 following replication of procedures of Phases 1 and 2 in Experiment 1. This ruled out the possibility that dogs simply lost motivation to participate in the task in later phases. These results suggest that not only dogs are highly skilled at understanding human pointing gestures, but also they make inferences about the reliability of a human who presents cues and consequently modify their behavior flexibly depending on the inference.

A reversed Ebbinghaus-Titchener illusion in bantams (Gallus gallus domesticus).

A disk surrounded by smaller disks looks larger, and one surrounded by larger disks looks smaller than reality. This visual illusion, called the Ebbinghaus-Titchener illusion, remains one of the strongest and most robust illusions induced by contrast with the surrounding stimuli in humans. In the present study, we asked whether bantams would perceive this illusion. We trained three bantams to classify six diameters of target disks surrounded by inducer disks of a constant diameter into "small" or "large". In the test that followed, the diameters of the inducer disks were systematically changed. The results showed that the Ebbinghaus-Titchener figures also induce a strong illusion in bantams, but in the other direction, that is, bantams perceive a target disk surrounded by smaller disks to be smaller than it really is and vice versa. Possible confounding factors, such as the gap between target disk and inducer disks and the weighted sum of surface of these figural elements, could not account for the subjects' biased responses. Taken together with the pigeon study by Nakamura et al. (J Exp Psychol Anim Behav Process 34:375-387 2008), these results show that bantams as well as pigeons perceive an illusion induced by assimilation effects, not by contrast ones, for the Ebbinghaus-Titchener types of illusory figures. Perhaps perceptual processes underlying such illusory perception (i.e., lack of contrast effects) shown in bantams and pigeons may be partly shared among other avian species.

Do pigeons (Columba livia) seek information when they have insufficient knowledge?

Seeking information in uncertain situations has been interpreted as evidence of metacognitive abilities. We examined whether pigeons could monitor their own knowledge states and seek new information when in need. In Experiment 1, we required the pigeons to learn novel sequences of responses for various trios of illustrations. On half of the trials, subjects were given the opportunity to ask for "hints" as to the next correct response in a sequence. If the subjects completed a trial correctly without any hints, they were rewarded with food and light. If the subjects sought one or more hints during the course of completing a trial correctly, they were rewarded either with food and light, or with light only. Incorrect responses resulted in a time-out. We analyzed when the pigeons sought hints. Two of four pigeons sought hints in early sessions more often than in the final sessions of learning novel sequences, and the frequency of hint-seeking was inversely correlated with accuracy on those trials in which hints were unavailable. In Experiment 2, however, the pigeons failed to generalize their "hint-seeking" behavior in a novel situation involving visual search as the primary task. In sum, the results suggest that this species might have an ability to differentiate between their own cognitive states of knowing and not knowing, although the evidence is inconclusive.

Bantams (Gallus gallus domesticus) also perceive a reversed Zöllner illusion.

Although pigeons have been shown to be susceptible to several size and length illusions, other avian species have not been tested intensively for illusory perception. Here we report how bantams perceive the Zöllner figure, in which parallel lines look nonparallel due to short crosshatches superimposed on the lines. Watanabe et al. (Cognition 119:137-141, 2011) showed that pigeons, like humans, perceived parallel lines as nonparallel but that the orientation of subjective convergence was opposite to that of humans. We trained three bantams to peck at the narrower (or wider) of the two gaps at the end of a pair of nonparallel lines. After adapting them to target lines with randomly oriented crosshatches (which result in no apparent illusion to humans), we tested the bantams' responses on randomly inserted probe trials, in which crosshatches that should induce the standard Zöllner-like illusion for humans replaced the randomly oriented ones. The results suggested bantams, like pigeons, perceive a reversed Zöllner illusion.

Breed Differences in Dopamine Receptor D4 Gene (DRD4) in Horses.

Genetic polymorphisms in genes related to neurotransmitters or hormones affect personality or behavioral traits in many animal species including humans. In domestic animals, the allele frequency of such genes has been reported to be different among breeds and it may account for breed differences in behavior. In this study, we investigated breed differences in horses in the dopamine receptor D4 gene (DRD4), which has been reported to affect horse personality. We collected samples from seven horse breeds including those native to Japan and Korea, and compared the sequence of the DRD4 exon3 region among these breeds. We found that there were two types of polymorphisms (VNTR and SNPs) in the exon3 region, and some of them seemed to be breed-specific. In addition, we found that the allele frequency of G292A, reported to be associated with horse personality, differed greatly between native Japanese horses and Thoroughbred horses. The frequency of the A allele which is associated with low curiosity and high vigilance, was much lower in native Japanese horses (Hokkaido, 0.03; Taishu, 0.08) than in Thoroughbreds (0.62). This difference may account for breed differences in personality or behavioral traits. Further studies of the function of these polymorphisms and their effect on behavior are indicated.

Cats Did Not Change Their Problem-Solving Behaviours after Human Demonstrations.

Humans learn by observing the behaviour of others, which can lead to more efficient problem-solving than by trial-and-error learning. Numerous studies have shown that animals, other than humans, are also capable of social learning. Dogs, as humans' closest companion animals, can learn to obtain rewards following behavioural demonstrations by humans. However, it is not known whether cats, who also live with humans, can learn how to solve problems by observing human behaviours. Three experiments were used to investigate whether cats could change their behaviour and gain rewards efficiently by observing a human demonstrating how to obtain food. In Experiment 1, a human demonstrated how to open a transparent drawer and take out the reward inside, but cats did not significantly follow the same method as the human. In Experiment 2a, a transparent tube device was used to make the operation easier for cats. However, cats were not influenced by the human behaviour. As the devices used in these experiments were transparent, meaning that the cats could see the food inside directly, they might have required strong inhibitory control. Therefore, in Experiment 2b the tube device was made opaque, and cats again observed the human demonstration. Nevertheless, the cats were not influenced by the human's behaviour. The results of these experiments indicate a lack of social learning, including imitation, from human behaviours in cats, at least in these experimental settings with food rewards. Other than their inherent ability, cats' biological characteristics and the experimental context may have contributed towards the negative results.

Capuchin monkeys (Cebus apella) use conspecifics' emotional expressions to evaluate emotional valence of objects.

Emotional expressions provide important clues to other individuals' emotional states, as well as the environmental situations leading to such states. Although monkeys often modify their behavior in response to others' expressions, it is unclear whether this reflects understanding of emotional meanings of expressions, or simpler, non-cognitive processes. The present study investigated whether a New World monkey species, tufted capuchin monkeys, recognize objects as elicitors of others' expressions. Observer monkeys witnessed another individual (demonstrator) reacting either positively or negatively to the contents of one of two containers and were then allowed to choose one of the containers. The observer preferred the container that evoked positive expressions in the demonstrator and avoided the container that evoked negative expressions. Thus, the monkeys appropriately associated the emotional valence of others' expressions with the container. This finding supports the view that the ability to represent others' emotions is not limited to humans and apes.

Incidental memory in dogs (Canis familiaris): adaptive behavioral solution at an unexpected memory test.

Memory processing in nonhuman animals has been typically tested in situations where the animals are repeatedly trained to retrieve their memory trace, such as delayed matching to sample, serial probe recognition, etc. In contrast, how they utilize incidentally formed memory traces is not well investigated except in rodents. We examined whether domestic dogs could solve an unexpected test based on a single past experience. In Experiment 1, leashed dogs were led to 4 open, baited containers and allowed to eat from 2 of them (Exposure phase). After a walk outside for more than 10 min, during which time the containers were replaced with new identical ones, the dogs were unexpectedly returned to the site and unleashed for free exploration (test phase). Eleven out of 12 dogs first visited one of the containers from which they had not eaten. In Experiment 2, two containers had food in them, one had a nonedible object, and the last one was empty. Dogs visited all 4 containers and were allowed to eat one of the food rewards in the Exposure phase. In the test phase, unleashed dogs first visited the previously baited container from which they had not eaten significantly more often than chance. These results demonstrate that in an unexpected, test dogs may retrieve "what" and "where" information about seen (now invisible) items from incidental memory formed during a single past experience.

Further tests of pigeons' (Columba livia) planning behavior using a computerized plus-shaped maze task.

Miyata and Fujita in 2008 reported that pigeons, trained to move a target square to a goal square by pecking, plan one step ahead while performing on a plus-shaped maze, that is, the birds frequently made errors to move the target toward the previous goal direction after the goal jumped to another arm. In the present study, pigeons' planning using this maze was further examined. In Experiment 1, when goals appeared at all three of the arms during solution, the birds did not choose the old goal at above chance. Reaction time data suggested that the birds decided which goal to choose after crossing the center point. In Experiment 2, after the goal jumped to another arm following a preview phase, some birds frequently moved in the direction of the old goal. These results suggest that pigeons may plan one step ahead but might have updated plans for each movement.

Acquisition of a same-different discrimination task by pigeons (Columba livia).

Four homing pigeons were trained to discriminate two figures simultaneously presented on an LCD screen. The figure was either a rectangle (A) or a square (B), and four combinations of the two figures, AA, AB, BA, BB, appeared in a pseudo-randomized order. The pigeons' task was to peck one of these figures based upon whether the two figures were identical or not. One pigeon successfully learned this discrimination, with proportions of correct responses above 90% in two consecutive sessions. Of the other birds, two performed above chance level but had difficulty meeting a learning criterion of above 80% in two consecutive sessions. All birds achieved this criterion when the combinations of figures presented were reduced to two. Results suggested that learning the present same-different discrimination is within the capacity of pigeons to a certain extent, although there exists considerable individual variation in the pigeons' skills to acquire complex discrimination.

Female dogs evaluate levels of competence in humans.

Dogs are highly sensitive to human behavior, and they evaluate us using both their direct experiences and from a third-party perspective. Dogs pay attention to various aspects of our actions and make judgments about, for example, social vs. selfish acts. However, it is unclear if dogs judge human competence. To investigate this issue, we showed dogs two experimenters manipulating a transparent container: one was good at removing the lid to take an object out of the container (Competent person), whereas the other was unsuccessful at this task (Incompetent person). After demonstrating their actions twice with different containers, both experimenters simultaneously tried to open a third container which contained food (Food condition; 30 dogs) or was empty (Empty condition; 30 dogs). Dogs in the Food condition looked at the Competent person longer than the Incompetent one, and female dogs in particular were more likely to approach the Competent person. In contrast, dogs in the Empty condition showed no preferences. This result suggests that dogs can recognize different competence levels in humans, and that this ability influences their behavior according to the first situation. Our data also indicate that more attention should be given to potential sex differences in dogs' social evaluation abilities.

Cats learn the names of their friend cats in their daily lives.

Humans communicate with each other through language, which enables us talk about things beyond time and space. Do non-human animals learn to associate human speech with specific objects in everyday life? We examined whether cats matched familiar cats' names and faces (Exp.1) and human family members' names and faces (Exp.2). Cats were presented with a photo of the familiar cat's face on a laptop monitor after hearing the same cat's name or another cat's name called by the subject cat's owner (Exp.1) or an experimenter (Exp.2). Half of the trials were in a congruent condition where the name and face matched, and half were in an incongruent (mismatch) condition. Results of Exp.1 showed that household cats paid attention to the monitor for longer in the incongruent condition, suggesting an expectancy violation effect; however, café cats did not. In Exp.2, cats living in larger human families were found to look at the monitor for increasingly longer durations in the incongruent condition. Furthermore, this tendency was stronger among cats that had lived with their human family for a longer time, although we could not rule out an effect of age. This study provides evidence that cats link a companion's name and corresponding face without explicit training.