Neural Darwinism and consciousness

Neural Darwinism (ND) is a large scale selectionist theory of brain development and function that has been hypothesized to relate to consciousness. According to ND, consciousness is entailed by reentrant interactions among neuronal populations in the thalamocortical system (the 'dynamic core'). These interactions, which permit high-order discriminations among possible core states, confer selective advantages on organisms possessing them by linking current perceptual events to a past history of value-dependent learning. Here, we assess the consistency of ND with 16 widely recognized properties of consciousness, both physiological (for example, consciousness is associated with widespread, relatively fast, low amplitude interactions in the thalamocortical system), and phenomenal (for example, consciousness involves the existence of a private flow of events available only to the experiencing subject). While no theory accounts fully for all of these properties at present, we find that ND and its recent extensions fare well.     

Tool-use learning in Tonkean macaques (Macaca tonkeana)

The transmission of tool use is a rare event in monkeys. Such an event arose in a group of semi-free-ranging Tonkean macaques (Macaca tonkeana) in which leaning a pole against the parks fence (branch leaning) appeared and spread to several males. This prompted us to test individual and social learning of this behavior in seven young males. In the first experiment, three males learned individually to obtain a food reward using a wooden pole as a climbing tool. They began using the pole to retrieve the reward only when they could alternatively experience acting on the object and reaching the target. In a second experiment, we first tested whether four other subjects could learn branch leaning after having observed a group-mate performing the task. Despite repeated opportunities to observe the demonstrator, they did not learn to use the pole as a tool. Hence we exposed the latter subjects to individual learning trials and they succeeded in the task. Tool use was not transmitted in the experimental situation, which contrasts with observations in the park. We can conclude that the subjects were not able to recognize the target as such. It is possible that they recognized it and learned the task individually when we alternated the opportunity to act upon the object and to reach the reward. This suggests that these macaques could then have associated the action they exercised upon the pole and the use of the pole as a means to reach the reward.     

Distance estimation in a dynamic simulated environment: a visual field dependence problem?

Egocentric distance estimation implies that the subject perceives his own location in the environment. In a simulated environment, subjects have to transpose perceptively their own observation point in order to assume their virtual body position. As only visual information specifies this position, their ability to perceive the camera viewpoint should be linked to the field dependence independence factor (FDI). Field-independent subjects underestimated the mid-distance between their own virtual body position and a far-located target; their bisection was located between the projective (2-D) and the simulated (3-D) mid-distance which indicates their difficulty in considering the in-depth simulated spatial references. High correlations between the vertical estimation in the rod-and-frame test and the egocentric-distance-estimation task (with shifted camera) suggest a similar perceptive process in both tasks. This result is confirmed by the better performances of the field-dependent subjects in this condition. In conclusion, we discuss the relationship between FDI and the sense of presence in virtual environments.     

School-year employment among high school students: effects on academic, social, and physical functioning

This study describes the effects of different weekly work intensity levels on adolescent functioning in a sample of 3,083 high school students in rural South Texas, where economically disadvantaged and Hispanic youth are heavily represented. Anonymous surveys were conducted in 10th- and 12th-grade students' classrooms in 1995. The following effects were associated with long hours of weekly employment during the school year: (1) decreased performance/engagement in school and satisfaction with amount of leisure time, and (2) increased health risk behaviors and psychological stress. The effects of school-year work on academic factors and health behaviors differed by grade, but not by race/ethnicity, parent education, or race/ethnicity and parent education considered together. It was concluded that parents and professionals should continue to monitor the number of weekly hours that students work during the school year.     

Cognitive behaviour therapy for eating disorders: a "transdiagnostic" theory and treatment

This paper is concerned with the psychopathological processes that account for the persistence of severe eating disorders. Two separate but interrelated lines of argument are developed. One is that the leading evidence-based theory of the maintenance of eating disorders, the cognitive behavioural theory of bulimia nervosa, should be extended in its focus to embrace four additional maintaining mechanisms. Specifically, we propose that in certain patients one or more of four additional maintaining processes interact with the core eating disorder maintaining mechanisms and that when this occurs it is an obstacle to change. The additional maintaining processes concern the influence of clinical perfectionism, core low self-esteem, mood intolerance and interpersonal difficulties. The second line of argument is that in the case of eating disorders shared, but distinctive, clinical features tend to be maintained by similar psychopathological processes. Accordingly, we suggest that common mechanisms are involved in the persistence of bulimia nervosa, anorexia nervosa and the atypical eating disorders. Together, these two lines of argument lead us to propose a new transdiagnostic theory of the maintenance of the full range of eating disorders, a theory which embraces a broader range of maintaining mechanisms than the current theory concerning bulimia nervosa. In the final sections of the paper we describe a transdiagnostic treatment derived from the new theory, and we consider in principle the broader relevance of transdiagnostic theories of maintenance.     

The future of the American Group Psychotherapy Association: whither we goest?

The author describes his perspective about what the future holds for the American Group Psychotherapy Association (AGPA). Utilizing Nitsun's (1996) construct of the "anti-group" as an organizing metaphor, he delineates the destructive forces both within and outside the organization that are currently affecting it, and then describes how they can be transformed into instruments for positive development. He suggests that the AGPA can and must continue to provide a "holding environment" (Winnicott, 1960) for professionals interested in working with people in groups. In addition, he asserts that the organization will build upon its remarkable response to the September 11, 2001 debacle in the United States to expand its services to those who have been traumatized. Beyond this, he underscores the importance of the AGPA consolidating and expanding its various educational offerings into a coherent package that will meet the needs of any and all who are interested in learning about how to work effectively with groups. In these and other ways, he contends that the AGPA will thereby confirm Nitsun's assertion that anti-group forces can be transformed, and that organizations that confront these forces constructively can not only survive but thrive.     

Instrumental and Pavlovian incentive processes have dissociable effects on components of a heterogeneous instrumental chain

Two experiments compared the effects of Pavlovian stimuli and incentive learning on the performance of a heterogeneous chain of instrumental actions. Using a Pavlovian-instrumental transfer design, the authors found that only a stimulus paired with the same outcome as that earned by performance of the chain produced positive transfer, an effect that was restricted to the action in the chain most proximal to reward delivery. In contrast, after a shift to a nondeprived state, only animals that had previously consumed the instrumental outcome when they were nondeprived decreased instrumental performance. Furthermore, this effect of the incentive learning treatment was limited to performance of the distal action. Together these data suggest that Pavlovian and instrumental incentive manipulations have dissociable effects on instrumental performance.