Brightness interactions between rods and cones

Two parafoveal test targets with different spectral compositions were matched in brightness to a fixed-luminance foveal reference target under scotopic adaptation conditions. The idea of the experiment was to find a reference luminance for which one of the matching test targets stimulated only rods while the other stimulated both rods and cones. If brightness was proportional to the linear sum of rod and cone responses, then the luminance of the matching rod+cone target would be predictably closer to rod threshold than would that of the rod target. The results were complicated by evidence that rod responses to the test targets selectively enhanced weak chromatic signals. Nevertheless, it was possible to show that cone activity never reduced the matching luminance as much as predicted by the additivity hypothesis, and sometimes even increased it. These findings suggest that cone activity can suppress brightness signals from rods.     

The debilitating effect of exposure to noncontingent escape: A test of the learned helplessness model

Two studies were conducted to test the hypothesis that exposure to non-contingent escape leads to performance deficits similar to those observed when subjects are exposed to noncontingent aversive outcomes from which there is no escape, and that causal attributions mediate these deficits. Previous attempts to produce “appetitive helplessness” (deficits resulting from exposure to noncontingent positive events) have been plagued by subjects' tendency to believe that they are responsible for positive events. In Experiment 1, 40 subjects were exposed to contingent or noncontingent noise escape trials. As predicted by the learned helplessness model, subjects who received inescapable noise performed less well on a subsequent anagram task than subjects exposed to escapable noise. Similarly, subjects who escaped from the noise owing to the benevolence of a powerful other rather than because of their own efforts, showed performance deficits paralleling those of the inescapable noise subjects. In Experiment 2, subjects who escaped an aversive tone through no effort of their own showed subsequent performance deficits, but globality of their self-reported attributions did not predict subsequent anagram performance. The results of these studies provide support for the hypothesis that uncontrollability, independent of the valence of a particular outcome, is responsible for helplessness deficits, but do not support the mediational role of attributions, at least in the laboratory.     

THE RELATION OF FOOD QUANTITY TO RUMINATION BEHAVIOR

Preliminary work suggested that the quantity of food ingested by retarded individuals who usually ruminated following meals was related to the frequency and duration of ruminating responses. This possible relation was experimentally examined by systematically varying food quantity from regular portions to satiation levels for three retarded individuals who exhibited high levels of ruminating. A clear functional relation of food quantity to ruminating emerged, with satiation procedures producing rapid and large decreases in the relatively high frequencies and durations of ruminating characteristic of baseline food quantity conditions.     

READING ABILITY AND PRIOR KNOWLEDGE AS PREDICTORS OF ELEVEN AND TWELVE YEAR OLDS' TEXT COMPREHENSION

The effect of prior knowledge on the comprehension of written prose paragraphs in intact, topic sentence deleted and topic and concluding sentence deleted conditions was studied. A methodology for determining prior knowledge is advanced. Subjects were average and high ability upper elementary age children. A 3 X 3 passage by treatment design was utilized. Strongest correlations were for ability and prior knowledge, and criterion measures of inferencing and summarizing. ANOVA yielded significant main effects for ability and all criterion measures except inference. Step‐wise regression analysis suggests prior knowledge as a better response predictor than ability on three of four criterion measures. The utility of an uncomplicated method for analyzing students' levels of prior knowledge valuable to researchers and classroom teachers is discussed.     

Learned helplessness and the detection of contingency: A direct test

Two studies tested a basic hypothesis of the learned helplessness model: That performance deficits associated with exposure to uncontrollable outcomes are directly mediated by an individual's perception of response-outcome independence. In the first experiment 48 subjects were exposed to noise bursts. For one experimental group, the termination of the noise was response-contingent. For five other groups, noise-burst termination was independent of subjects' responses. These five groups varied in the number of trials on which they received positive feedback: As predicted, subjects overestimated the amount of control they had over noise termination as a positive linear function of the amount of noncontingent positive feedback they received. Although subjects exposed to either noncontingent positive or negative feedback showed subsequent performance deficits on an anagrams task, the expected relation between perceived control and subsequent performance failed to emerge. These findings were replicated in a second experiment. In addition, subjects' locus, stability, and globality attributions failed to predict subsequent performance. These results call into question the central premises of helplessness theory: That perceived uncontrollability and causal attributions mediate learned helplessness.     

Effects of nutritional and mechanical properties of food on ruminative behavior.

Previous studies have identified a reliable relation between the quantity of food ingested and ruminating in profoundly retarded individuals and have established some parametric characteristics of this relation. The present study investigated three different properties of food that may influence this relation. Experiment 1 examined the role of stomach distention produced by including in the subject's diet wheat bran in amounts equivalent to and exceeding the calculated amount of crude fiber in the starch-satiation diet reported by Rast, Johnston, Drum, and Conrin (1981) and Rast, Johnston, and Drum (1984). There was a decrease in ruminating, although this decrease was smaller and more gradual than in the starch-satiation condition. Experiment 2 showed that increasing calories without increasing food volume resulted in a gradual and moderate decrease in ruminating. Experiment 3 replicated and extended the first two experiments by varying both caloric intake and stomach distention as well as oropharyngeal and esophageal stimulation in a different sequence of conditions. All variables exerted some control over responding. However, the large and immediate effects of the starch-satiation procedure occurred only when subjects were permitted to consume unlimited quantities.     

Translating policy principles into practice to improve health care access for adults with intellectual disabilities: a research review of the past decade

This article extracts principles from two Surgeon General reports, Closing the Gap: A National Blueprint to Improve the Health of Persons with Mental Retardation (2002) and Call to Action to Improve the Health and Wellness of Persons with Disabilities (2005), and combines them with the Objectives from Chapter 6 of Healthy People 2010 to create a policy framework. This framework is used to review literature from the past decade on access to health care and health promotion for persons with intellectual and developmental disabilities (IDD). Review of the literature indicates an emerging evidence base for health promotion programs for persons with IDD. Research in health care and health promotion access requires improvements in surveillance and measurement of quality of life, as well as increased participation of persons with IDD and their families in its implementation. While international guidelines for primary health care have been developed for people with IDD, US guidelines are specialty focused and address specific conditions. Despite its recognized importance, there is surprisingly little information on training programs for health care providers to improve care of persons with IDD. Financing of health care continues to threaten access to comprehensive care for persons with IDD, particularly regarding coordination of care and availability of providers who accept Medicaid patients. Community-based sources of health care have been slow to emerge, and there is clear need for assumption of responsibility for providing care to persons with IDD. Future US policy should include consideration of environmental factors in health care access.