Journal of Comparative Psychology

A comparative view of face perception.
Face perception serves as the basis for much of human social exchange. Diverse information can be extracted about an individual from a single glance at their face, including their identity, emotional state, and direction of attention. Neuropsychological and functional magnetic resonance imaging (fMRI) experiments reveal a complex network of specialized areas in the human brain supporting these face-reading skills. Here we consider the evolutionary roots of human face perception by exploring the manner in which different animal species view and respond to faces. We focus on behavioral experiments collected from both primates and nonprimates, assessing the types of information that animals are able to extract from the faces of their conspecifics, human experimenters, and natural predators. These experiments reveal that faces are an important category of visual stimuli for animals in all major vertebrate taxa, possibly reflecting the early emergence of neural specialization for faces in vertebrate evolution. At the same time, some aspects of facial perception are only evident in primates and a few other social mammals, and may therefore have evolved to suit the needs of complex social communication. Because the human brain likely utilizes both primitive and recently evolved neural specializations for the processing of faces, comparative studies may hold the key to understanding how these parallel circuits emerged during human evolution. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Species differences in executive function correlate with hippocampus volume and neocortex ratio across nonhuman primates.
A persistent debate in behavioral research is whether brain size or architecture relates to cognitive performance. A growing body of evidence has demonstrated correlations between brain size and ecological and behavioral tasks. These studies are premised on a causal link between brain size and cognitive function, although this association has little empirical backing. We show, for a set of 46 species from 17 primate genera, that competence on a series of eight executive function cognitive tasks both correlate across tasks and with brain size and architecture across species. Our model selection approach showed that, although several measures of brain component volumes are significantly associated with performance, hippocampus size is the best predictor of overall performance. The best performing model also includes total brain size and relative neocortex size. Additionally, absolute measures are much more predictive of performance than relative measures of brain and brain component size. These results are consistent with the hippocampus' role in learning, and the executive brain (neocortex) being important for problem solving and consolidation. Our findings challenge and extend those of previous analyses by clarifying the relationship between overall brain size and specific regional volumes. They also suggest that commonly used indices of encephalization, such as residuals of brain volume regressed on body size, may confound rather than clarify matters. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Visual contrast modulates maturation of camouflage body patterning in cuttlefish (Sepia pharaonis).
Camouflage is the primary defense behavior in cephalopods. It is known that cuttlefish immediately after hatching are capable of showing various body patterns for concealing themselves, however recent studies suggest that maturation of camouflage body patterns is faster for cuttlefish (Sepia officinalis) reared in enriched environments than those reared in impoverished environments. Since camouflage patterning in cephalopods is predominately visually driven, this study specifically investigates effects of the rearing background contrast on the maturation of body patterns in cuttlefish (Sepia pharaonis). Newly hatched animals were separated into two cohorts, one reared in a uniform-gray background (low-contrast, or L group) and the other raised in a black/white checkerboard background (high-contrast, or H group). At Weeks 2, 4, 6, 8, 10, and 12, cuttlefish were placed individually either on uniform or checkerboard substrates to examine their body patterns. Animals from both L and H groups appear to show moderate disruptive patterns on the checkerboard and less disruptive on the uniform background at Week 2. Throughout development, however, cuttlefish from the H group showed stronger disruptive patterns than that of the L group on the checkerboard background at Weeks 10 and 12. In interesting findings, cuttlefish from both L and H groups showed similar strength but different disruptive components on the uniform background in later postembryonic stages. These results suggest that the maturation of camouflage body patterns in S. pharaonis is at least in part affected by visual contrast of their rearing backgrounds, although environmental complexity or social interaction is also likely to be involved in this process. This also implies that early visual experience could exert its effect on the seemingly preprogrammed behaviors such as camouflage body patterning in cephalopods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Capuchins (Cebus apella) can solve a means-end problem.
Three capuchin monkeys (Cebus apella) were tested on a 2-choice discrimination task designed to examine their knowledge of support, modeled after Hauser, Kralik, and Botto-Mahan's (1999) experiments with tamarins. This task involved a choice between 2 pieces of cloth, including 1 with a food reward placed on its surface, and a second cloth with the food reward next to its surface. After reliably solving the basic problem, the capuchins were tested with various alternations of the original food reward and cloth. The capuchins were able to solve the initial task quickly, and generalize their knowledge to additional functional and nonfunctional variations of the problem. In comparison to the tamarins previously tested on this problem (Hauser et al., 1999), the capuchins were able to reach criterion faster during the training and food size conditions and showed a greater ability to inhibit reaching toward larger food rewards that were unavailable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Chimpanzee (Pan troglodytes) consolation: Third-party identity as a window on possible function.
Consolation, that is, postconflict affiliative contact by a bystander toward a recipient of aggression, has acquired an important role in the debate about empathy in great apes because it has been proposed that the reassuring behavior aimed at distressed parties reflects empathetic arousal. However, the function of this behavior is not fully understood. The present study tests specific predictions about the identity of bystanders on the basis of a database of 1102 agonistic interactions and their corresponding postconflict periods in two outdoor-housed groups of captive chimpanzees (Pan troglodytes). We found that recipients of aggression were more likely to be contacted by their own “friends” than by “friends” of the aggressor and that frequent targets of aggression were not more likely to offer consolation than were nontargets of aggression. These findings support the stress reduction hypothesis rather than two proposed alternatives, that is, the opponent relationship repair hypothesis and the self-protection hypothesis. Our results provide further support for relationship quality as a fundamental underlying factor explaining variation in the occurrence of consolation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Attention to emotional scenes including whole-body expressions in chimpanzees (Pan troglodytes).
Real-life situations provide rich sets of cues that viewers evaluate in terms of their emotional significance. In this study, chimpanzees (Pan troglodytes) viewed a movie depicting naturalistic scenes involving the whole-body expressions of conspecifics to examine how nonhuman primates perceived the combination of these cues and how each cue contributed to the overall perception. Viewing time was measured while the chimpanzees watched movie clips without sound. Among scenes depicting neutrality, general excitement, agonism, and playfulness, chimpanzees looked longest at those depicting agonism. This bias toward agonistic scenes may indicate an attentional sensitivity toward threat/fear-related negative situations among chimpanzees. The effect disappeared when the images were scrambled, ruling out the possible effect of pixel-level properties on the results. In addition, the follow-up analyses revealed that the effect was independent of the presentation order and of the number of individuals in each clip. The manipulation of playback speeds had little effect on the looking times. The elimination of facial cues slightly influenced the looking times but did not change the strong bias toward agonistic scenes. This robustness of the main effect against image manipulations may indicate that the chimpanzees attended directly to the contextual information implied by the cues rather than to the cues per se (e.g., facial expressions, speed of movements). (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Maternal separation alters social odor preference development in infant mice (Mus musculus).
This study examined whether daily periods of maternal separation during the first two weeks of life would decrease attraction to familiar nest odors in CD-1 mice 10 and 14 days old. We also investigated whether placing a group of mice (Mus musculus) in nest shavings during the 180-min separation period would mitigate possible separation-induced deficits. The maternal separation procedure has been widely used as a rodent model for the effects of inconsistent or inadequate early caretaking on human development. From postnatal day (PND) 1 to 14, litters were separated from the dam, but not littermates for either 15 or 180 min, or were facility-reared controls. Control, facility-reared mice preferred home-cage nest to clean familiar shaving odors on PND 10, but not PND 14. In contrast, home-cage nest odors attracted maternally separated mice on both test days. Our results suggest that maternal separation maintains the olfactory tether to the nest in a period when the attraction normally begins to weaken. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Rats (Rattus norvegicus) in a water maze learn both an egocentric trajectory and landmarks.
In two experiments we investigated the extent to which rats (Rattus norvegicus) use an egocentric trajectory and landmarks to locate a goal. In Experiment 1 we trained groups to locate the hidden platform in a water maze with either 1 of 3 or 3 of 3 predictive landmarks, and with either a random or fixed egocentric trajectory. A choice test revealed that regardless of the landmark configuration, rats relied on a directional, egocentric trajectory, when it was available, to locate the platform. In Experiment 2 we found that adding four predictive landmarks following training with a constant egocentric trajectory did not alter rats' initial attention to the trajectory. We conclude that the presence of nonpredictive landmarks in a predictive array did not affect the use of landmarks. With a blocking design, rats used initially an egocentric path, then landmarks. These results add to the notion that animals use available spatial cues sequentially. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Behavioral measures of auditory streaming in ferrets (Mustela putorius).
An important aspect of the analysis of auditory “scenes” relates to the perceptual organization of sound sequences into auditory “streams.” In this study, we adapted two auditory perception tasks, used in recent human psychophysical studies, to obtain behavioral measures of auditory streaming in ferrets (Mustela putorius). One task involved the detection of shifts in the frequency of tones within an alternating tone sequence. The other task involved the detection of a stream of regularly repeating target tones embedded within a randomly varying multitone background. In both tasks, performance was measured as a function of various stimulus parameters, which previous psychophysical studies in humans have shown to influence auditory streaming. Ferret performance in the two tasks was found to vary as a function of these parameters in a way that is qualitatively consistent with the human data. These results suggest that auditory streaming occurs in ferrets, and that the two tasks described here may provide a valuable tool in future behavioral and neurophysiological studies of the phenomenon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Do bantams (Gallus gallus domesticus) experience amodal completion? An analysis of visual search performance.
Whereas many mammals (some primates and mice) experience amodal completion, previous data split for avian species. However, experimental procedures have been quite different among the species, and thus a direct comparison of various avian species in the same experimental situation is needed. We tested whether bantams (Gallus gallus domesticus) would complete partly occluded figures using a visual search task on the touch monitor, which was successfully used in our previous study with pigeons. First, we trained 3 participants to search for a notched red diamond (a target) among complete diamonds (distracters). Next, white squares accompanied each figure with a small gap of a fixed size. In test, the location of the accompanying white squares sometimes changed. In some trials, the white squares exactly covered, or “occluded,” the notched portion of the target. Humans are known to have great difficulty in finding such targets due to “automatic” completion of the notched part. However, bantams met no such difficulty at all. This result and the demonstration by Forkman (1998) of hens' amodal completion of figures placed on a perspective background, suggest that the perspective cue may have an important role in amodal completion in this species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Behavioral science, engineering, and poetry revisited.
Forty years ago, Lehrman (1971) identified 2 orientations to the study of animal behavior. The natural history orientation conducted field and lab research designed to reveal how animals cope with the circumstances of their natural environment. Such research reveals the diversity among different types of animals and differences between the world of animals and the world of humans (i.e., “poetry”). In contrast, the anthropocentric orientation studies animals either to generate animal-derived general laws applicable to humans or to provide experimental information that, for ethical and practical reasons, cannot be acquired from human research. The primary motivation for the anthropocentric orientation is to provide workable models for investigating specifically human problems (i.e., “engineering”). Evidence is presented from the study of bird song that demonstrates the contribution that the “poetic” approach can make to anthropocentric (“engineering”) concerns. (PsycINFO Database Record (c) 2010 APA, all rights reserved)

Journal of Comparative Psychology - Vol 124, Iss 3