Perception of depth from shading in infant chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>)

We investigated the ability to perceive depth from shading, one of the pictorial depth cues, in three chimpanzee infants aged 4–10 months old, using a preferential reaching task commonly used to study pictorial depth perception in human infants. The chimpanzee infants reached significantly more to three-dimensional toys than to pictures thereof and more to the three-dimensional convex than to the concave. Furthermore, two of the three infants reached significantly more to the photographic convex than to the photographic concave. These infants also looked longer at the photographic convex than the concave. Our results suggest that chimpanzees perceive, at least as early as the latter half of the first year of life, pictorial depth defined by shading information. Photographic convexes contain richer information about pictorial depth (e.g., attached shadow, cast shadow, highlighted area, and global difference in brightness) than simple computer-graphic graded patterns. These cues together might facilitate the infants perception of depth from shading.     

Perceiving an object and its context in different cultures: a cultural look at new look

Abstract - In two studies, a newly devised test (framed-line test) was used to examine the hypothesis that individuals engaging in Asian cultures are more capable of incorporating contextual information and those engaging in North American cultures are more capable of ignoring contextual information. On each trial, participants were presented with a square frame, within which was printed a vertical line. Participants were then shown another square frame of the same or different size and asked to draw a line that was identical to the first line in either absolute length ( absolute task ) or proportion to the height of the surrounding frame ( relative task ). The results supported the hypothesis: Whereas Japanese were more accurate in the relative task, Americans were more accurate in the absolute task. Moreover, when engaging in another culture, individuals tended to show the cognitive characteristic common in the host culture.     

Cultural variation in implicit independence: An extension of Kitayama et al. ()

Previous research shows that European Americans are consistently more independent (or less interdependent) than Japanese when implicit indices are used to assess independence (vs. interdependence). The present work extended this evidence by including a novel implicit association test (IAT), as an index of implicit attitude towards independence and interdependence. Consistent with the previous findings, as compared to Japanese, Americans were significantly higher in multiple indices of implicit independence (vs. interdependence) including personal (vs. social) self‐definition, experience of disengaging (vs. engaging) emotions and personal (vs. social) form of happiness. Furthermore, as compared to Japanese, Americans had a significantly more positive implicit attitude towards independence assessed with the IAT. As also observed in the previous research, explicit measures showed inconsistent cross‐cultural patterns. Lastly, we observed little statistical within‐culture coherence among the implicit measures of independence (vs. interdependence), consistent with a view that the implicit indices capture alternative ways for individuals to achieve the cultural mandate of independence or interdependence.     

Effects of element separation on perceptual grouping by humans (Homo sapiens) and chimpanzees (Pan troglodytes): perception of Kanizsa illusory figures

The processing of Kanizsa-square illusory figures was studied in two experiments with four humans and two chimpanzees. Subjects of the two species were initially trained to select a Kanizsa-square illusory figure presented in a computerized two-alternative forced choice task. After training, adding narrow closing segments to the pacman inducers that composed the Kanisza illusory figures lowered performance in both chimpanzees and humans, suggesting that the discrimination could be controlled by the perception of illusory forms. A second experiment assessed transfer of performance with five sets of figures in which the size of the inducers and their separation were manipulated. Only for chimpanzees was performance directly controlled by separation, suggesting that chimpanzees are more sensitive than humans to the separation between visual elements. Accepted after revision: 15 August 2001 Electronic Publication     

Looking compensates for the distance between mother and infant chimpanzee

The development of visual interaction between mother and infant has received much attention in developmental psychology, not only in humans, but also in non-human primates. Recently, comparative developmental approaches have investigated whether the mechanisms that underlie these behaviors are common in primates. In the present study, we focused on the question of whether chimpanzee mother and infant replace physical contact with visual contact. To test this hypothesis, we measured non-synchronous looking ('looking') between mother and infant. A unique setting, in which the mother chimpanzee stayed in one location and the infant chimpanzee moved freely, allowed us to analyze the relation between the visual interaction and the distance of a mother-infant pair during the first year of life. Our results showed that 'looking' increased when body contact decreased or when the distance between mother and infant increased. We also show a behavioral sequence of typical 'secure base' behavior, a behavior characterized by the infant regularly returning to its mother when exploring the environment. These findings imply that attachment between mother and infant chimpanzee appears to develop in a similar fashion as in humans.     

Inclusion of additional studies yields different conclusions: Comment on Sedikides, Gaertner, & Vevea (2005), Journal of Personality and Social Psychology

In a Journal of Personality and Social Psychology article, Sedikides, Gaertner and Vevea (2005) presented two meta-analyses that included eight papers to investigate the question of whether people from Eastern cultures self-enhance more for traits that they view to be important compared to those that they view as unimportant. The results supported their hypothesis: Self-enhancement appears to be pancultural. However, this conclusion is severely compromised by six relevant papers that are not included in their meta-analyses. Importantly, all of these six studies contradicted their hypothesis. When complete meta-analyses are conducted which include all of the relevant papers, a very different pattern of results emerges. Eastern and Western cultures do not differ from each other in the pattern of their self-enhancement of independent and interdependent traits. Furthermore, whereas Westerners self-enhanced significantly more for traits that they viewed to be especially important, East Asians did not. Contrary to the Sedikides et al. (2005) suggestion, the existing evidence suggests substantial cross-cultural variation in self-enhancement, with Westerners being far more self-enhancing than Easterners. Reasons for the conflicting pattern of findings across methods and meta-analyses are discussed.     

Plasticity of ability to form cross‐modal representations in infant Japanese macaques

In a previous study, Adachi, Kuwahata, Fujita, Tomonaga & Matsuzawa demonstrated that infant Japanese macaques (Macaca fuscata) form cross‐modal representations of conspecifics but not of humans. However, because the subjects in the experiment were raised in a large social group and had considerably less exposure to humans than to conspecifics, it was an open question whether their lack of cross‐modal representation of humans simply reflected their lower levels of exposure to humans or was caused by some innate restrictions on the ability. To answer the question, we used the same procedure but tested infant Japanese macaques with more extensive experience of humans in daily life. Briefly, we presented monkeys with a photograph of either a monkey or a human face on an LCD monitor after playing a vocalization of one of these two species. The subjects looked at the monitor longer when a voice and a face were mismatched than when they were matched, irrespective of whether the preceding vocalization was a monkey's or a human's. This suggests that once monkeys have extensive experience with humans, they will form a cross‐modal representation of humans as well as of conspecifics.     

The primal warrior: Outgroup threat priming enhances intergroup discrimination in men but not women

Previous evidence suggests that, compared with females, male psychology and behavior is more strongly oriented toward intergroup conflict and competition. This study tested whether male coalitional psychology is so deeply ingrained that it could be activated even by subtle cues in the environment suggesting intergroup conflict. We used a priming method to test if being unwittingly exposed to an offensive message from an outgroup member in one type of intergroup context (i.e., inter-cultural) would enhance male’s and female’s intergroup discrimination in reward allocation in a completely irrelevant intergroup context (i.e., artificial laboratory group). The results showed that, as predicted, the outgroup threat priming enhanced discrimination in men but not women.     

Case study of a one‐sided attack by multiple troop members on a nontroop adolescent male and the death of Japanese macaques (Macaca fuscata)

An adolescent wild male Japanese macaque (Macaca fuscata), following Kinkazan A troop, was attacked one‐sidedly by multiple members of the troop. The victim was identified as PI, and was estimated to be seven±one year old. The aggressive interaction was recorded by video camera until the end. Although at least 16 troop members approached PI more than once, only three males (one adult, two adolescents) of A troop attacked him. PI kept crouching throughout the attack, then escaped to the shore and dived into the sea. The interaction continued for more than one hour. PI was found dead a few hours after the end of interaction. The damage caused by the assailants was not the direct cause of PI's death; it was due to hypothermia caused by drifting in the sea. PI's life history was reconstructed from past records. PI was a normal adolescent male who migrated from an all‐male group around B₁ troop and started ranging around A troop. The aggressive interaction is believed to be a typical example of conflict between troop males and a nontroop male. The interaction period was very long compared with previous reports on such conflicts among Japanese macaques. PI kept crouching in open areas, exposing himself as a potential competitor for the resources of the troop, and did not show any submissive or reconciliatory behavior toward the troop males. This may be why the troop males did not stop the attack. Aggr. Behav. 35:334–341, 2009. © 2009 Wiley‐Liss, Inc.