Time courses in visual-information processing: Some empirical evidence for inhibition

Summary In the literature two different views on the time course of activation of recognition units — hypothetical units that represent identity information — are proposed. The first view assumes that the recognition units accumulate activation gradually over time. The second assumes that the activation levels increase fast initially and then start to decrease. Hagenzieker and Van der Heijden (1990) have proposed a more general information-processing model, which is compatible with both views. In this model a treshold determines what type of time course will be obtained. For below-threshold-activation values a gradual accumulation of activation will be found; for above-threshold values activation levels will first increase and then, because of inhibition, decrease. This model served as a starting-point for the present paper. Elaboration of this model led to two testable hypotheses with regard to identification performance. The first prediction is that evidence for inhibition should be observed only under relatively bright luminance conditions. The second is that, given inhibition, the amount of the effect of this inhibition should increase over time. A partial-report bar-probe task was used to test the predictions. The experiment involved two luminance conditions and the information was sampled at two different moments in time. To control for possible localization artefacts a digit-naming task was also used. Evidence for inhibition was found in both luminance conditions. In accordance with the model the amount of the effect of inhibition increased over time.     

The internal clock: evidence for a temporal oscillator underlying time perception with some estimates of its characteristic frequency

Evidence for the proposition that human time perception is determined by an internal clock is largely indirect. It would strengthen the case for this hypothesis if a model for the internal clock were available from which predictions could be derived and tested, and if the basic parameter of such a model, the frequency at which the clock runs, could be estimated. A model for an internal temporal pacemaker is briefly described and its properties are explored by computer simulation. Results are obtained that provide a basis for predicting that, under appropriate conditions, interference between an imposed rhythm and the frequency of a temporal oscillator may cause perturbations in temporal judgment which are related to the characteristic frequency of that oscillator. Experimental data are reported which appear to demonstrate such an interference pattern. These results allow some estimates of the characteristic frequency of the temporal oscillator to be obtained.     

Interpersonal loss and self-mutilation

Self-mutilation was hypothesized to increase in frequency during periods of interpersonal loss in a treatment program for seriously disturbed adolescents. The study examined changes in the frequency of acts of self-mutilation, aggression, and running away for 32 teenagers who experienced interpersonal loss when staff members left employment. Data were collected for a 4-year period. Statistical findings indicated that the frequency of self-mutilation increased significantly during the time period of anticipated loss, 2 weeks prior to staff terminations. There was no significant increase in the frequency of self-mutilation immediately following the staff terminations. Also, there was no significant change in the rates of aggression or running away either before or after the loss events. It was concluded that the time of anticipated loss was the period of highest risk for these adolescents in terms of self-mutilative behavior.     

Disordered eating in women of color

It has been assumed that the occurrence of eating disorders in American racial minority groups are rare. Indeed, whereas the cultural context may afford “protection” to the group, it does not necessarily protect specific individuals. Individuals within each racial/ethnic group are subject to the standards of the dominant culture, particularly when the culture-of-origin is devalued by the dominant culture. Social, familial, and individual factors which contribute to disorders eating symptomatology are discussed. Discussions of obstacles to detecting eating disorders and guidelines for developing more inclusive theory of and treatment of persons with eating disorders is included.     

Light-dark variation and changes across the lactational period in the behaviors of undisturbed mother and infant guinea pigs (Cavia porcellus)

Lactating guinea pigs (Cavia porcellus) and their litters were observed by videophotography across the light/dark cycle at 1, 11, 21, and 31 days postpartum. The highest level of behavioral activity was seen in the dark, particularly in the hour after light offset. This circadian pattern was evident from Day 1 in mothers and from Day 11 in pups. Contact between mothers and pups was inversely related to activity, occurring more frequently during light. Maternal grooming of pups occurred on Day 1 and then declined: self-grooming by pups increased across days. Intake of solid food and water by pups occurred on Day 1 and increased thereafter. A nearly complete transition from nursing to independent ingestion was observed between 21-31 days of age. Overall, we document several ontogenetic changes in young guinea pigs and demonstrate that under laboratory conditions mother and infant guinea pigs exhibit a nocturnal activity pattern.     

The Future of Psychology in Departments of Psychiatry

Health care reform has put increasing pressure on faculty of medical schools to become self-supporting. Opportunities for clinical revenue will decrease, but psychologists who are able to generate research funding will become increasingly competitive, albeit as mercenaries, i.e., capable of paying their own way plus generating a profit to support departmental operations and educational programs. Changes in the health care system signal an end to psychiatry's paternalistic relationship to psychology and present opportunities for psychology proactively to influence its future role in health care. Research, political action, and revised scientific mission, models, and roles represent important strategies in the redefining of psychology as a basic science and major profession in health care.     

Isoluminance and contingent color aftereffects

In the typical induction of the orientation-contingent color aftereffect (CCAE), the stimuli are composed of elements that differ in both color and luminance. Three experiments are reported that show that chromatic contrast between stimulus elements is insufficient for the induction of the orientation-CCAE and that luminance contrast is necessary. These experiments expand on previous research concerned with the role of luminance contrast in the induction of orientation-CCAEs by eliminating alternative explanations.