Manual dexterity in the gorilla: bimanual and digit role differentiation in a natural task

The manipulative actions of mountain gorillas Gorilla g. beringei were examined in the context of foraging on hard-to-process plant foods in the field, in particular those used in tackling thistle Carduus nyassanus. A repertoire of 72 functionally distinct manipulative actions was recorded. Many of these actions were used in several variants of grip, finger(s) and movement path, both by different individuals and by the same individual at different times. The repertoire appears somewhat greater than that observed in comparable studies of monkeys, but a far more striking difference is found in the use of differentiated actions in concert. Mountain gorillas routinely and frequently deal with problems that involve: (1) bimanual role differentiation, with the two hands taking different roles but synchronized in time and space, and (2) digit role differentiation, with independent control of parts of the same hand used for separate purposes at the same time. The independent control that allows these abilities, so crucial to human manual constructional ability, is apparently general in African great apes. Role differentiation, between and within the hand, is evidently a primitive characteristic in the human arsenal of skills. Accepted after revision: 6 April 2001 Electronic Publication     

EAST AND WEST IN THE FACE OF TECHNOLOGICAL CHANGE

Abstract. Technological changes affect Western culture in three ways: the ratio between the lifetimes of technologies and the human lifetime is inverted; the three principal realms of human life (the home, the workplace, and leisure activity), as well as political systems, are affected; and the cohesion of the social body is threatened. The impact on Eastern culture is softened by a clearer role assigned to school, the resulting level of education, and the influence of Confucian ethics. However, acculturation will vary among countries, depending on the communication ability in the respective societies and the degree of development of social cellular structures, which are the most able to manage complexity.     

Consistency Orientation and Models of Social Behavior: Is It Not Time for West to Meet East

The study examined the cultural differences in inconsistency-reducing behaviors by testing the reactions of 110 Japanese and 169 American college students to the inconsistencies arising from a difference of opinion with a significant other on ego-involving issues. It was predicted that (1) the Japanese sample would show more inconsistency support than will an American sample; (2) The American sample will show more preference for active inconsistency-reducing responses than will the Japanese sample; (3) on the hypothesis that contemporary social psychology's models of humans is based upon the American stereotype of the "typical American," the first two predictions will be more strongly confirmed by comparing the American subjects' stereotype of the "typical American" than by comparing their own reported choices. The findings generally supported the first two predictions and strongly supported the third one.     

Between Hope and Fear: A Dialogueon the Peace Process in the Middle East and the Polarized Israeli Society

The restarting of the peace process in the Middle East in 1993 raised the hopes of many in Israel for progress toward resolution of the Arab-Israeli conflict. Yet the Oslo agreements raised not only hope but also fears. The latter triggered a deep schism and polarization within the Israeli society. These led to a delegitimization campaign by those opposing the peace process that was directed both against the rationale underlying the change of policies and its architects Foreign Minister Shimon Peres and Prime Minister Yitzhak Rabin. The escalation of polarization saw the assassination of Prime Minister Rabin and the seeming paradox of an election victory for the political rightist parties' candidate, Binyamin Netanyahu. Two Israeli social scientists present in dialogue form alternative psychopolitical perspectives and interpretations of the evolution of these critical events.     

Speech and bimanual hand organization in adult stutterers and nonstutterers

A multivariate approach was used to investigate the relationship between speech fluency and bimanual handwriting in right-handed male stutterers and nonstutterers. Handedness was determined by the Harris Test of Lateral Dominance. Subjects were required to write the numbers 1 through 12 simultaneously, as quickly as possible. Speech measures were derived from the Stuttering Severity Instrument and from a reading passage. Stutterers performed more poorly than nonstutterers on all speech measures. There were no differences in bimanual handwriting performance for the dominant hand. However, stutterers performed more poorly than nonstutterers in nondominant handwriting. There were no relationships between speech measures and bimanual handwriting for stutterers or nonstutterers. Some stutterers performed better on the handwriting task than did some nonstutterers. It is suggested that disorganization in interhemispheric integration functions may be a more fundamental problem in stuttering than is incomplete cerebral dominance.     

The effect of context during word perception in schizophrenic patients

Hospitalized chronic and acute schizophrenics were compared with age- and social-status-matched controls on word perception tests to measure the effect of context on recognition thresholds. In Experiment 1 the method of J. Morton (1964, British Journal of Psychology, 55, 165-180) was adopted to see how related and unrelated contexts influenced word recognition thresholds when both context and stimulus word were presented visually. Experiment 2 was an auditory analog of Experiment 1 and in addition the chronic schizophrenics were selected on the basis of a presence or absence of auditory hallucinations. The influence of context on perceptual thresholds was quite normal in all schizophrenics. However, analysis of the incorrect responses elicited showed that some schizophrenic subjects do produce bizarre or irrelevant responses or perseveration to a greater extent than their controls. These results are explained in terms of automatic and strategic modes of information processing. The automatic processes responsible for the adjustment of perceptual thresholds operate normally in schizophrenics but response production which demands strategic selection and editing of responses is prone to malfunction which results in the observed deviations in the normal use of language.     

Context and companion's behavior as determinants of cooperation and competition in school-age children

Information about the social context and a companion's actions were studied as determinants of cooperation and competition in middle childhood. In Experiment 1, first-, third-, and fifth-grade children were told that they would play a board game with another same-age, same-sex child (actually a bogus companion). The experimenter's instructions established shared rewards or winner-take-all as outcome conditions. Preprogrammed responses—100% cooperative or 100% competitive—provided information about the companion's actions. Results revealed that the companion's responses alone determined cooperation and competition among the first graders. Third graders used both types of information. Fifth graders, however, demonstrated a bias to respond cooperatively whenever a cooperative cue was present. In Experiment 2, first-grade subjects were given extra rehearsal of the game strategies, a scorekeeping procedure for use during the game, or a combination of the two. Results indicated that, under these conditions, younger subjects were able to use the instructions about reward distribution as well as the companion's actions in guiding their social behavior.     

An analysis of situation and person components of jealousy

Previous studies on jealousy have focused on person factors or on situational factors, but none has compared their relative importance. Two studies are presented which analyze the contributions of persons, situations, and their interaction, with respect to jealous reactions. The first study examined intraperson variability in the intensity of jealous responses of 302 males and females when presented with four types of hypothetical jealousy situations (work, family, social, and sexual). The results of the first study supported a dispositional explanation of jealousy (i.e., substantial person and situational variance). In addition, a sizable interaction effect was revealed. Study 2 examined the nature of this interaction for sexual jealousy. Jealousy situations were broken down by distinguishing between the event, characteristics of the partner, and the relationship as separate components of the situation. Seventy-one female respondents indicated their perception of threat and their degree of upset when considering the same hypothetical jealousy-evoking events with three different partners. A substantial person component was found. In addition, responses to the jealousy-evoking events were found to vary as a function of which partner was being considered. The second study demonstrated that aspects of the relationship (i.e., relative involvement) were more important than personality characteristics of the partner in determining this intrasubject variability in the intensity of jealous rections.     

Aversive properties of the negative stimulus during learning with and without errors

In a successive discrimination four groups of pigeons were trained to discriminate between red and green. The groups differed with respect to the procedure used to introduce S?: Early-Progressive, Early-Constant, Late-Progressive, and Late-Constant. The aversive properties of S? were measured by an escape response in which a single peck at a second key terminated S? for 10 sec and darkened the chamber. The correlation between the aversive and error-producing properties of extinction was zero. More errors occurred when S? was introduced abruptly at a constant intensity while more timeouts from S? occurred when S? was introduced late. The procedure for introducing S? rather than the number of responses to S? appears crucial in determining how aversive S? becomes.     

CT scan and neuropsychological correlates of Alzheimer's disease and Huntington's disease

"Cortical" and "subcortical" dementia syndromes differ in areas of primary neuropathology and clinical characteristics. Conventional CT scan interpretation, visual inspection of pictures, has not been useful in studying dementia. Recent studies of the digitally stored CT attenuation values have found systematic variations with normal aging and aphasia subtypes. In this study of numerical CT scan information in four Alzheimer's Disease and two Huntington's Disease patients, a double dissociation of frontal and temporal lobe density values was found, and a significant correlation was found between left temporal lobe density and verbal ability measures in the Alzheimer's Disease patients.