Abstract: Mirror self-recognition (MSR), investigated in primates and recently in non-primate species, is considered a measure of self-awareness. Nowadays, the only reliable test for investigating MSR potential skills consists in the untrained response to a visual body mark detected using a reflective surface. Here, we report the first evidence of MSR at group level in horses, by facing the weaknesses of methodology present in a previous pilot study. Fourteen horses were used in a 4-phases mirror test (covered mirror, open mirror, invisible mark, visible colored mark). After engaging in a series of contingency behaviors (looking behind the mirror, peek-a-boo, head and tongue movements), our horses used the mirror surface to guide their movements towards their colored cheeks, thus showing that they can recognize themselves in a mirror. The analysis at the group level, which 'marks' a turning point in the analytical technique of MSR exploration in non-primate species, showed that horses spent a longer time in scratching their faces when marked with the visible mark compared to the non-visible mark. This finding indicates that horses did not see the non-visible mark and that they did not touch their own face guided by the tactile sensation, suggesting the presence of MSR in horses. Although a heated debate on the binary versus gradualist model in the MSR interpretation exists, recent empirical pieces of evidence, including ours, indicate that MSR is not an all-or-nothing phenomenon that appeared once in phylogeny and that a convergent evolution mechanism can be at the basis of its presence in phylogenetically distant taxa.

Abstract: Most birds rely on imprinting and experience with conspecifics to learn species-specific recognition cues. Australian brush-turkeys (Alectura lathami) do not imprint and form no bonds with parents. They hatch asynchronously, disperse widely and meet juvenile conspecifics at an unpredictable age. Nevertheless, in captivity, hatchlings respond to other chicks. A recent study, which involved the use of robotic models, found that chicks prefer to approach robots that emit specific visual cues. Here, we evaluated their response to acoustic cues, which usually play an important role in avian social cognition. However, in simultaneous choice tests, neither 2-day-old nor 9-day-old chicks preferred the choice arm with playback of either chick or adult conspecific calls over the arm containing a silent loudspeaker. Chicks of both age classes, however, scanned their surroundings more during chick playback, and the response was thus consistent in younger and older chicks. We also presented the chicks with robotic models, either with or without playback of chick calls. They did not approach the calling robot more than they did the silent robot, indicating that the combination of visual and acoustic cues does not evoke a stronger response. These results will allow further comparison with species that face similar cognitive demands in the wild, such as brood parasites. Such a comparative approach, which is the focus of cognitive ecology, will enable us to further analyse the evolution and adaptive value of species recognition abilities.

Abstract: Laterality is now known to be an ubiquitous phenomenon among the vertebrates. Particularly, laterality of auditory processing has been demonstrated in a variety of species, especially songbirds and primates. Such a hemispheric specialization has been shown to depend on factors such as sound structure, species specificity and types of stimuli. Much less is known on the possible influence of social familiarity although a few studies suggest such an influence. Here we tested the influence of the degree of familiarity on the laterality of the auditory response in the domestic horse. This species is known for its social system and shows visible reactions to sounds, with one or two ears moving towards a sound source. By comparing such responses to the playback of different conspecific whinnies (group member, neighbor and stranger), we could demonstrate a clear left hemisphere (LH) preference for familiar neighbor calls while no preference was found for group member and stranger calls. Yet, we found an opposite pattern of ear side preference for neighbor versus stranger calls. These results are, to our knowledge, the first to demonstrate auditory laterality in an ungulate species. They open further lines of thought on the influence of the social “value” of calls and the listener's arousal on auditory processing and laterality.

Abstract: Teaching is a powerful form of social learning, but there is little systematic evidence that it occurs in species other than humans. Using long-term video archives the foraging behaviors by mother Atlantic spotted dolphins (Stenella frontalis) were observed when their calves were present and when their calves were not present, including in the presence of non-calf conspecifics. The nine mothers we observed chased prey significantly longer and made significantly more referential body-orienting movements in the direction of the prey during foraging events when their calves were present than when their calves were not present, regardless of whether they were foraging alone or with another non-calf dolphin. Although further research into the potential consequences for the naive calves is still warranted, these data based on the maternal foraging behavior are suggestive of teaching as a social-learning mechanism in nonhuman animals.

Abstract: Two chimpanzees used a joystick to collect dots, one at a time, on a computer monitor (see video-clip in the electronic supplementary material), and then ended a trial when the number of dots collected was equal to the Arabic numeral presented for the trial. Both chimpanzees performed substantially and reliably above chance in collecting a quantity of dots equal to the target numeral, one chimpanzee for the numerals 1-7, and the second chimpanzee for the numerals 1-6. Errors that were made were seldom discrepant from the target by more than one dot quantity, and the perceptual process subitization was ruled out as an explanation for the performance. Additionally, analyses of trial duration data indicated that the chimpanzees were responding based on the numerosity of the constructed set rather than on the basis of temporal cues. The chimpanzees' decreasing performance with successively larger target numerals, however, appeared to be based on a continuous representation of magnitude rather than a discrete representation of number. Therefore, chimpanzee counting in this type of experimental task may be a process that represents magnitudes with scalar variability in that the memory for magnitudes associated with each numeral is imperfect and the variability of responses increases as a function of the numeral's value.