Humans have a tendency to perceive inanimate objects as animate based on simple motion cues. Although animacy is considered as a complex cognitive property, this recognition seems to be spontaneous. Researchers have found that young human infants discriminate between dependent and independent movement patterns. However, quick visual perception of animate entities may be crucial to non-human species as well. Based on general mammalian homology, dogs may possess similar skills to humans. Here, we investigated whether dogs and humans discriminate similarly between dependent and independent motion patterns performed by geometric shapes. We projected a side-by-side video display of the two patterns and measured looking times towards each side, in two trials. We found that in Trial 1, both dogs and humans were equally interested in the two patterns, but in Trial 2 of both species, looking times towards the dependent pattern decreased, whereas they increased towards the independent pattern. We argue that dogs and humans spontaneously recognized the specific pattern and habituated to it rapidly, but continued to show interest in the 'puzzling' pattern. This suggests that both species tend to recognize inanimate agents as animate relying solely on their motions.

The effects of emotionally valenced events on sleep physiology are well studied in humans and laboratory rodents. However, little is known about these effects in other species, despite the fact that several sleep characteristics differ across species and thus limit the generalizability of such findings. Here we studied the effect of positive and negative social experiences on sleep macrostructure in dogs, a species proven to be a good model of human social cognition. A non-invasive polysomnography method was used to collect data from pet dogs ( = 16) participating in 3-hour-long sleep occasions. Before sleep, dogs were exposed to emotionally positive or negative social interactions (PSI or NSI) in a within-subject design. PSI consisted of petting and ball play, while NSI was a mixture of separation, threatening approach and still face test. Sleep macrostructure was markedly different between pre-treatment conditions, with a shorter sleep latency after NSI and a redistribution of the time spent in the different sleep stages. Dogs' behaviour during pre-treatments was related to the macrostructural difference between the two occasions, and was further modulated by individual variability in personality. This result provides the first direct evidence that emotional stimuli affect subsequent sleep physiology in dogs.

Perceptual animacy is the tendency for observers to represent inanimate objects as animate, based on simple motion cues. Several features of the chasing pattern can elicit animacy perception and, similarly to adult humans, dogs perceive dots showing this pattern as animate. Here, we used moving objects with a heading alignment (isosceles triangles) to investigate whether human and dog behavior continues to show similarities following such slight but important change in the pattern. We hypothesized that a heading alignment would facilitate animacy perception in both species in a similar manner. We displayed chasing and nonchasing (independent) motions side-by-side on a screen in two subsequent trials (Trial 1 and 2). Looking duration at each pattern as well as frequency of gaze shifting between the patterns was measured. Humans looked at the independent motion for longer already during Trial 1; however, dogs looked at this pattern longer only during Trial 2, whereas during Trial 1, their looking time increased toward the chasing pattern. Gaze shifting was observed in humans more often in both trials than in dogs. Although ultimate preference for the independent motion suggests rapid perception of the chasing pattern directing gaze in both species toward the “unrecognized” pattern, there was an initial interspecies difference. We suggest that different behavior across humans and dogs could be explained by ecological differences, although the role of differences in visual strategies, irrespective of perception of animacy, cannot be excluded.

Social evaluation is a mental process that leverages the preference toward prosocial partners (positivity bias) against the avoidance of antisocial individuals (negativity bias) in a cooperative context. The phenomenon is well-known in humans, and recently comparative investigations looked at the possible evolutionary origins. So far social evaluation has been investigated mainly in non-human and human primates and dogs, however, there are few data on the presence of negativity/positivity bias in client-cleaner reef fish interactions as well. Unfortunately, the comparative approach to social evaluation is hindered by conceptual and procedural differences in experimental studies. By reviewing current knowledge on social evaluation in different species, we aim to point out that the capacity for social evaluation is not restricted to humans alone; however, its building blocks (negativity and positivity bias) may be more widespread separately. Due to its importance in survival, negativity bias likely to be widespread among animals; however, there has been less intensive selective pressure for the identification of prosocial companions, thus the latter ability may have emerged only in certain social species. We present a general framework and argue that negativity and positivity bias evolve independently and can be considered as social evaluation only if a unified behavior and cognitive system deals with both biases in concert.

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