Social Density and Affiliative Tendency as Determinants of Dormitory Residential Outcomes

The questionnaire responses of both high social density and low social density dormitory residents, divided into high and low groups on affiliative tendency, were examined. Although both high and low affiliates experienced more satisfaction living in low social density dorms, which were associated with higher levels of social interaction than high social density dorms, levels of reported stress varied as a function of both social density and affiliation. High affiliates experienced more, while low affiliates experienced less, stress in the low social density dorm than in the high social density dorm. Results were discussed in terms of the possession of differential coping skills with respect to achieving independence (in the low social density dorm) and dealing with overload from strangers (in the high social density dorm).     

Perceptual independence of the hemifields in children and adults

Second graders, fifth graders, and college students were shown words and letters under conditions designed to assess the extent to which stimuli presented to one hemifield and consequently one hemisphere are affected by stimuli projected to the other hemifield. Hemifield, and by implication, hemispheric independence was more likely to occur for letters and among the children, and in each case hemifield asymmetries in performance were also less pronounced. These results were discussed in terms of developmental models of perceptual asymmetry and hemispheric interaction.     

Effects of instructional constraints on human fixed-interval performance

Several groups of human subjects were exposed to a variety of experimental conditions involving a fixed-interval 27-second schedule of reinforcement in compound with instructions to constrain in the number of responses within the interreinforcement interval and/or the duration of the experimental session. One group was further exposed to a contingency involving the placement of responses within the IRI. A diversity of patterns of performance was observed, including those typically associated with animal subjects exposed to FI schedules. Generally, the imposition of instructions to minimize session duration reduced post-reinforcement pausing and increased overall reinforcement density from those levels obtained with only instructions to expend a given number of responses per reinforcer. The results are seen to underscore the sensitivity of human fixed-interval performance and the contribution of extra-experimental contingencies.     

Escape from freedom: Choosing not to choose in pigeons

Preference for the availability of food-reinforcement alternatives was investigated with Rachlin and Green's (1972) concurrent-chains self-control paradigm. The terminal link of one chain made available a choice between immediate access to food for T seconds and delayed access to food for 4 seconds. The terminal link of the other chain provided only delayed access to food. When T was reduced to .25 seconds, pigeons began to select the delayed-access key in both terminal links. Even so, the pigeons strongly preferred constraint over choice. This effect could not be accounted for by differences in the actual amount of food obtained in the terminal links, by avoidance of the immediate-reinforcement key when not presented as part of a choice, or by avoidance of a multi-key terminal link. Rather, constraint was preferred over freedom. Apparently, the preference for choice is determined by the particular type of choice offered.     

A jackknife test of homogeneity of variance with paired replicates data

A nonparametric test of dispersion with paired replicates data is described which involves jackknifing logarithmic transformations of the ratio of variance estimates for the pre- and post-treatment populations. Results from a Monte Carlo simulation show that the test performs well underH _o and has good power properties. Examples are given of applying the procedure on psychiatric data.A referee called our attention to valuable references which related to our work, and he suggested the inclusion of competing jackknife procedures into our studies.     

Case specificity of the stimulus probability effect

Four memory scanning experiments investigated the effect of the probability of occurrence of one case of a letter (e.g., “A”) on response time to the other case of that same letter (“a”). There was no effect: Responses to one case of a letter did not depend on the probability of occurrence of the other case of the letter. This finding indicates that facilitation of visual encoding by high probability of occurrence is not caused by increased activation at the level of the name code. Previous results rule out the possibility that facilitation occurs at the level of feature detectors responding to the individual visual features of the high-probability stimuli, and these results were replicated in the present experiments. It appears that facilitation is caused by activation along specific routes by which visual features activate letter names. This conclusion has implications for the locus of effect of stimulus probability in models of letter coding     

Somatic and autonomic indexes of recovery from electroconvulsive shock-induced amnesia in rats

Autonomic response indexes of experimental amnesia have recently been found to have higher electroconvulsive shock (ECS) intensity thresholds and steeper retrograde gradients than have traditional somatic indexes. The present studies examined the hypothesis that recovery from somatically indexed experimental amnesia depends upon the existence of autonomically available residual memory. In a between-subjects design, a 200-mA ECS was used to produce amnesia for a tone-footshock pairing as indicated by lick suppression, defection, and bradycardia. The next day, these amnesic animals received a reminder footshock outside of the training apparatus, which was found to restore memory on a test trial 24 hr later. The behavior of control groups indicated that this reminder effect was due to the restoration of specific memory rather than systemic consequences of treatment. With a within-subjects design, a second experiment obtained a reminder effect in animals individually shown to be "fully" amnesic by all three response indexes monitored. A third experiment varied the intensity of the reminder footshock and revealed that the different memory indexes examined do not have reminder-footshock thresholds inversely related to their initial resistance to amnesia. The results support a retrieval-failure view of experimental amnesia and suggest that the same fundamental physiological processes underlie both autonomically indexed memory and somatically indexed memory.     

Saccade latency in children and adults: Effects of warning interval and target eccentricity

Saccadic response latency to the onset of an eccentric target was studied in children (mean age = 8.7) and adults. The independent variables investigated were fixation-light offset to target-light onset warning interval (0, 100, 300, and 600 msec) and target eccentricity (5° or 15°). Both children and adults showed shorter saccade latencies under warning-interval conditions. Children were found to have longer latencies than adults with 0 or 100 msec warning intervals but to respond with as short or shorter latencies with 300 or 600 msec warning intervals. Target eccentricity effects did not interact with age, and occurred only with a lower target intensity. Children defined as poor readers could initiate a response as quickly as good readers but were less able to maintain fixation-light fixation prior to target onset.