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     

The Use of Standard Parenting Management Training in Addressing Disruptive Mood Dysregulation Disorder: A Pilot Study

Journal of Contemporary Psychotherapy - Parent management training has demonstrated effectiveness in the treatment of child behavioural issues and associated conduct difficulties. Anger,...     

The Role of Situational Interviews in Fostering Positive Reactions to Selection Decisions

We investigated the effect of interview format and employment equity program strength on perceptions of fairness. We used job seekers and vignettes to test the hypotheses. The participants reported lukewarm support for employment equity programs. The use of a situational interview in the selection process of an organisation that had adopted an employment equity program contributed to higher perceptions of fairness vis‐à‐vis the use of an unstructured interview. The results also showed that the inclusion of a situational interview in the selection process mitigated negative reactions to the selection decision when a strong employment equity program was in place as well as when a female visible minority was hired. Nous avons évalué l'impact sur la perception de justice du style d'entretien et de la rigueur d'une charte d'équité relative à l'emploi. On a fait appel à des demandeurs d'emploi et utilisé un test de jugement situationnel pour éprouver les hypothèses. Les répondants se sont montrés peu enthousiastes en ce qui concerne les chartes d'équité relatives à l'emploi. Le choix d'un entretien structuré dans le processus de sélection d'une organisation qui avait adopté une charte d'équité relative à l'emploi a amélioré la perception de justice portant sur un entretien ordinaire. Il apparaît aussi que la présence d'un entretien structuré dans le processus de sélection atténuait les réactions négatives consécutives au résultat de la sélection quand existait une sérieuse charte d'équité relative à l'emploi et quand était embauchée une minorité féminine non négligeable.     

Interpretation of the personality inventory for children-revised (PIC-R): Influence of cognitive impairment

The Personality Inventory for Children-Revised (PIC-R) is a parent-report measure of social-emotional adjustment for children 3 to 16 years of age. The present study examined the clinical value of the PIC-R by exploring the impact of age and developmental status on PIC-R profiles, particularly on the Psychosis (PSY) scale, within a sample of preschool and school-age children referred for assessment of suspected cognitive impairment and learning problems. Compared to school-age children, significantly more preschoolers obtained elevated scores on the Psychosis scale; those preschoolers with cognitive impairments were even more likely to obtain significantly elevated Psychosis scale scores, despite the absence of diagnosed childhood psychosis. No significant relationship was found between Psychosis scale elevations and cognitive impairment in the school-age group. The PIC-R was moderately accurate in identifying cognitively impaired preschoolers but only minimally accurate in identifying cognitively impaired school-age children.     

Effects of D-amphetamine on response acquisition with immediate and delayed reinforcement.

The present study examined in 8-hour sessions the effects of d-amphetamine (1.0, 5.6, and 10 mg/kg) on the acquisition of lever-press responding in rats that were exposed to procedures in which water delivery was delayed by 0, 8, or 16 seconds relative to the response that produced it. Both nonresetting- and resetting-delay conditions were studied. Although neither shaping nor autoshaping occurred, substantial levels of operative-lever responding developed under all conditions in which responses produced water. The lowest dose (1.0 mg/kg) of d-amphetamine either had no effect on or increased operative-lever pressing, whereas higher doses typically produced an initial reduction in lever pressing. Nonetheless, overall rates of operative-lever pressing at these doses were as high as, or higher than, those observed with vehicle. Thus, response acquisition was observed under all reinforcement procedures at all drug doses. In the absence of the drug, most responding occurred on the operative lever when reinforcement was immediate. Such differential responding also developed under both nonresetting- and resetting-delay procedures when the delay was 8 seconds, but not when it was 16 seconds. d-Amphetamine did not affect the development of differential responding under any procedure. Thus, consistent with d-amphetamine's effects under repeated acquisition procedures, the drug had no detrimental effect on learning until doses that produced general behavioral disruption were administered.     

Brightness indention: A novel compression mechanism in the luminance-brightness mapping

In a previous study, Schouten and Blommaert (1995) explicitly showed that brightness constancy implies a substantial compression in the luminance-brightness mapping. Here it is argued that additional compression mechanisms are required for scenes with large luminance ranges. To trace these, a series of experiments was conducted which involved expansion of the luminance range. We used a simple spatial configuration consisting of a disk on a contourless homogeneous surround (Ganzfeld). The contrast between the disk and Ganzfeld acted as the independent variable, while the size of the disk was parametrically varied. Sequential dichoptical brightness matches with a reference were carried out for both the disk and the surround. The results reveal a compression mechanism which we termbrightness indention. This indention, which has not previously been reported in the literature, only occurs if the Ganzfeld is less luminous than the disk, and it takes the form of a brightness decrease of the immediate surroundings of the disk.