Longitudinal Development of the Automatic Postural Response in Infants

In this longitudinal study, the development of automatic postural responses elicited during stance following perturbation of the support surface was investigated. Infants (N = 9) unable to stand without support were tested initially: follow-up tests were performed until the infants were able to stand and walk independently. Surface electromyographic recordings of leg and trunk muscle activity following a postural perturbation induced by a forward or backward translation of the support surface were made for each infant. Muscle onset latencies following the perturbation and the proportion of trials in which muscle activity was recorded were determined. First, infants activated appropriate muscles either in isolation or in pairs and then combined these muscles into functional synergies. Although activation of all three postural muscles was recorded in infants before they were able to stand and walk independently, the three-muscle response was not consistent in the youngest children. The proportion of trials eliciting muscle activity continued to increase (p <.O5) after infants began to walk independently, with postural muscle activity recorded in virtually every trial by late independent walking. Thus. the automatic postural response elicited during stance was shown to begin with activity in single or paired muscles, followed by activation of the postural muscles in functional synergies. These data illustrate the progressive development of an effective sensory-motor organization.     

Creativity in an Indigenous Afro-Arab Islamic Culture: The Case of Sudan

The present study attempted to appraise creativity in the indigenous Sudanese culture, which is formed by a complex integration and interaction of various social and cultural factors, mainly of African, Arab, and Islamic origin. More specifically, the study investigated the concept of creativity in a conformist culture, the problem of using Western tests and the problem of modernization. Also it attempted to find answers to some crucial questions: What is the scope available for creative expression in a tight sociocultural system? How could creativity coexist with conformity? What form of creativity can exist in the indigenous sociocultural system?     

Personality and Coping: Three Generations of Research

ABSTRACT This article introduces the Journal of Personality 's special issue on coping and personality. It first presents a historical overview of the psychological study of how people cope with stress and identifies three generations of theory and research: (a) the psychoanalysts and the ego development school, which tended to equate personality and coping strategies; (b) the transactional approach, which appeared in the 1960s and emphasized situational and cognitive influences on coping while downplaying the role of individual differences; and (c) the most recent, "third generation," whose work is represented in this special issue and focuses on the role of personality in coping while maintaining strong operational distinctions among coping, personality, appraisal, and adaptational outcomes. This introduction concludes with a discussion of unresolved conceptual and methodological issues and a brief orientation to the third-generation articles that follow in this special issue.     

Detecting a nonevent: Delayed presence-versus-absence discrimination in pigeons

Eight pigeons were trained on a delayed presence-versus-absence discrimination paradigm in which a sample stimulus was presented on some trials but not on others. If a sample was presented, then a response to one choice key produced food. If no sample was presented, a response to the other choice key produced food. The basic finding was that performance remained constant and well above 50% correct on no-sample trials as the retention interval increased, whereas performance dropped precipitously (to below 50% correct) on sample trials. In the second phase of the experiment, all of the trials were no-sample trials, and reinforcers were delivered probabilistically for one group of pigeons and according to time-based schedules for the other group. The exact reinforcement probabilities used in Phase 2 were those calculated to be in effect on no-sample trials in Phase 1 (according to a discrete-state model of performance). Subjects did not show exclusive preference for the richer alternative on no-sample trials in the first phase, but those in the probabilistic group developed near-exclusive preference for the richer alternative during the second phase. These data are inconsistent with the predictions of the discrete-state model, but are easily accommodated by an account based on signal detection theory, which also can be applied effectively to discrimination of event duration and the “subjective shortening” effect.