Prestige Affects Cultural Learning in Chimpanzees

Humans follow the example of prestigious, high-status individuals much more readily than that of others, such as when we copy the behavior of village elders, community leaders, or celebrities. This tendency has been declared uniquely human, yet remains untested in other species. Experimental studies of animal learning have typically focused on the learning mechanism rather than on social issues, such as who learns from whom. The latter, however, is essential to understanding how habits spread. Here we report that when given opportunities to watch alternative solutions to a foraging problem performed by two different models of their own species, chimpanzees preferentially copy the method shown by the older, higher-ranking individual with a prior track-record of success. Since both solutions were equally difficult, shown an equal number of times by each model and resulted in equal rewards, we interpret this outcome as evidence that the preferred model in each of the two groups tested enjoyed a significant degree of prestige in terms of whose example other chimpanzees chose to follow. Such prestige-based cultural transmission is a phenomenon shared with our own species. If similar biases operate in wild animal populations, the adoption of culturally transmitted innovations may be significantly shaped by the characteristics of performers

Racial Group Membership Is Associated to Gaze-Mediated Orienting in Italy

Viewing a face with averted gaze results in a spatial shift of attention in the corresponding direction, a phenomenon defined as gaze-mediated orienting. In the present paper, we investigated whether this effect is influenced by social factors. Across three experiments, White and Black participants were presented with faces of White and Black individuals. A modified spatial cueing paradigm was used in which a peripheral target stimulus requiring a discrimination response was preceded by a noninformative gaze cue. Results showed that Black participants shifted attention to the averted gaze of both ingroup and outgroup faces, whereas White participants selectively shifted attention only in response to individuals of their same group. Interestingly, the modulatory effect of social factors was context-dependent and emerged only when group membership was situationally salient to participants. It was hypothesized that differences in the relative social status of the two groups might account for the observed asymmetry between White and Black participants. A final experiment ruled out an alternative explanation based on differences in perceptual familiarity with the face stimuli. Overall, these findings strengthen the idea that gaze-mediated orienting is a socially-connoted phenomenon

Scio Ergo Sum: Knowledge of the Self in a Nonhuman Primate

The pressures of developing and maintaining intricate social relationships may have led to the evolution of enhanced cognitive abilities in many social nonhuman species, particularly primates. Knowledge of the dominance ranks and social relationships of other individuals, for example, is important in evaluating one’s position in the prevailing affiliative and dominance networks within a primate society and could be acquired through direct or perceived experience. Our analysis of allogrooming supplants among wild bonnet macaques had revealed that individual females successfully evaluate social relationships among other group females and possess egotistical knowledge of their own positions, relative to those of others, in the social hierarchy. These individuals, therefore, appeared to have abstracted and mentally represented their own personal attributes as well as those of other members of the group. Bonnet macaques also seem to recognise that other individuals have beliefs that may be different from their own, manipulate another individual’s actions and beliefs in a variety of social situations, and selectively reveal or withhold information from others—capabilities displayed by certain individuals that became evident in the course of our earlier studies on tactical deception in the species. In conclusion, the ability to develop belief systems and form mental representations, generated by direct personal experience, suggests a rather early evolutionary origin for fairly sophisticated cognitive capabilities, characterised by an objectified self with limited regulatory control over more subjective levels of self-awareness, in cercopithecine primates, pre-dating those of the great apes. We, therefore, argue, in this review, that bonnet macaques might represent an intermediate stage in the evolution of self-awareness, a process which began with the subjective awareness that characterises most, if not all, higher animal species and culminates in the most sophisticated form of symbolic self-awareness, apparently the hallmark of the human species alone

The XI National Congress of the Italian Society of Psychopathology: Psychiatric therapy. A problem of freedom - Rome, February 21-25, 2006: SOPSI Prize 2006. Reduced neuronal density in the fusiform cortex of schizophrenic subjects

Background: Reduced fusiform gyrus volume has been reported in MRI studies of schizophrenia. Evidence from brain lesions suggests the fusiform cortex is involved in object naming and categorisation. Reduced fMRI activation is seen during emotion recognition tasks in schizophrenia. Methods: We assessed cell size, shape and density of pyramidal and non-pyramidal neurons and glial cell density in layers 3 and 5 of fusiform cortex from 11 (6 females, 5 males) control subjects and 10 (5 females, 5 males) subjects with schizophrenia. Systematic random sampling in the left and right hemispheres provided size and shape of 120 pyramidal and 120 non-pyramidal cells per case by outlining at a point where the nucleolus was clearly visible. For estimating cell densities, 450 to 600 cells were counted per subject. Results: Pyramidal cell density was reduced in schizophrenia in both layers, in both hemispheres with no effect by sex. Non-pyramidal cell density was reduced in layer 3, in the left hemisphere and this was greatest in females. Non-pyramidal cells were larger in schizophrenia. Glial cell density was unchanged. Conclusions: Reduced pyramidal and non-pyramidal neuron density in the fusiform cortex relates to findings of reduced fusiform cortex volume and is consistent with reduced cell density in other regions reported in the literature. Pyramidal cell loss in fusiform cortex may contribute to reduced activation in imaging studies. Non-pyramidal neurons may be enlarged in schizophrenia as compensation for reduced density