Aging and perception of visual form from temporal structure

In this study, the authors examined age-related changes in participants' ability to perceive global spatial structure defined by temporal fine structure among elements undergoing rapid, irregular change. Participants were also tested on a task involving form recognition from luminance contrast and on a task dependent on perception of 3-dimensional shape from motion. Compared with young adults, older individuals were less sensitive to spatial form defined by temporal structure. In contrast, older observers performed as well as young adults on the other two tasks that were not dependent on temporal sensitivity, ruling out nonsensory factors as the cause of the deficits on the temporal structure task. This selective deficit may reveal reduced sensitivity within the temporal impulse response of the aging visual system, a deficit that could be related to reduced effectiveness of neural inhibition.     

Children's understanding of ownership transfers

An understanding of ownership entails the recognition that ownership can be transferred permanently and the ability to differentiate legitimate from illegitimate transfers. Two experiments explored the development of this understanding in 2-, 3-, 4- and 5-year olds, using stories about gift-giving and stealing. The possibility that children use simple biases to identify owners, such as a first possessor, current possessor or a loan bias, was also investigated. Five-year olds appropriately acknowledged a permanent transfer of ownership in the case of giving but not stealing. Four-year olds allowed permanent transfers but struggled to differentiate legitimate from illegitimate transfers. Many 4-year olds allowed adults, but not children, to keep property that had been stolen. Two- and 3-year olds exhibited a first possessor bias for both stories. We conclude that, by 5 years of age, children possess a mature understanding of ownership transfer whereas younger children are prone to biases.     

Spatial interactions in binocular rivalry.

Observers tracked binocular rivalry between a pair of small, foveally viewed gratings whose orientation differed between the 2 eyes. In Experiment 1, a textured annulus surrounding 1 eye's grating increased the total duration of exclusive visibility of the grating only when the grating-annulus separation was less than 0.5 degree. In Experiment 2, observers tracked the visibility of a monocular annulus that surrounded a foveally viewed grating that was either engaged in rivalry or fused with a grating alone viewed by the other eye. The visibility of the annulus was greater when the grating it surrounded was not undergoing rivalry fluctuations. In Experiment 3, the predominance of a rival grating was greater when the contours in the surrounding annulus were orthogonal to those of the rival grating. In Experiment 4, total exclusive visibility of a given grating-annulus target was greater when the grating and the annulus contained the same orientation.     

What masks utrocular discrimination

Utrocular discrimination, the ability to judge which eye has received monocular stimulation, was studied under conditions designed to reduce the salience of the cue mediating this discrimination. In one series of experiments, these conditions involved reducing the likelihood of motor command signals, overwhelming the motor command centers, and triggering motor command signals for both eyes. Those results indicate that utrocular discrimination is not mediated by ocular movements or command signals. In a second series of experiments, a visual masking paradigrn was used. A monocular test grating appeared superimposed upon a background of binocular masking noise, which was presented either simultaneously with the target or at some interval preceding or following the target (asynchronous masking). When presented simultaneously, the binocular masking noise interfered with utrocular performance, but only when the noise contained spatial frequencies near the test frequency. Masking functions obtained under conditions of asynchronous masking indicated that the time course of the forward and backward masking changed with spatial frequency. Finally, a sustained masking pattern that was ineffective in reducing utrocular performance could be made effective by pulsing the mask simultaneously with the target. Taken together, these results implicate a transient response to the target onset as a critical factor in generating the cue for successful utrocular discrimination. This conclusion may account for the fact that utrocular discrimination falls off for normal observers as the spatial frequency of the target grating increases above 4 cycles/deg.     

Work-Unit Structure and Processes and Job-Related Stressors as Predictors of Managerial Burnout1

Research on the antecedents of burnout has focused largely on such job-related stressors as role conflict, ambiguity, and overload. The present study expands the focus by also examining the role of organizational structure and processes, notably work-unit standardization, formalization, and communication. It is hypothesized that the effect of organizational structure and processes on burnout is in fact largely mediated by job-related stressors. Self-report data from supervisors and managers in a public welfare setting provide strong support. More broadly, these findings suggest that the impact of “macro” variables on the individual is at least partially mediated by “micro” variables. Specific associations between aspects of structure/process and stressors and between stressors and dimensions of burnout are also examined.     

Similarities and differences between MMPI and MMPI-2 applications to the assessment of posttraumatic stress disorder

The purpose of this study was to address the question: Is the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) comparable to the original MMPI in its applicability to the assessment of posttraumatic stress disorder (PTSD) among Vietnam combat veterans? The question was addressed by administering both the original MMPI and MMPI-2 to 29 subjects classified as meeting Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.; DSM-III-R) criteria for PTSD and comparing MMPI and MMPI-2 scores in terms of: degree of association, code-type congruence, diagnostic hit rates (when compared to two other clinical samples, and one normal sample), and congruence of the Keane PTSD Scale (PK). Results reveal highly significant correlations between MMPI and MMPI-2 basic scales for the PTSD sample as well as congruence in 2-point codes comparable to previous studies. The MMPI-2 was found to identify effectively PTSD subjects from the other groups. Results also showed a high degree of association between the MMPI and MMPI-2 in regard to PK scores, although minor differences were found in PK raw scores between the two tests. Overall, the findings suggest a high degree of comparability between the MMPI and MMPI-2 in the assessment of PTSD.     

The interplay between stereopsis and structure from motion

In a series of psychophysical experiments, an adaptation paradigm was employed to study the influence of stereopsis on perception of rotation in an ambiguous kinetic depth (KD) display. Without prior adaptation or stereopsis, a rotating globe undergoes spontaneous reversals in perceived direction of rotation, with successive durations of perceived rotation being random variables. Following 90 sec of viewing a stereoscopic globe undergoing unambiguous rotation, the KD globe appeared to rotate in a direction opposite that experienced during the stereoscopic adaptation period. This adaptation aftereffect was short-lived, and it occurred only when the adaptation and test figures stimulated the same retinal areas, and only when the adaptation and test figures rotated about the same axis. The aftereffect was just as strong when the test and adaptation figures had different shapes, as long as the adaptation figure contained multiple directions of motion imaged at different retinal disparities. Nonstereoscopic adaptation figures had no effect on the perceived direction of rotation of the ambiguous KD figure. These results imply that stereopsis and motion strongly interact in the specification of structure from motion, a result that complements earlier work on this problem.     

Developmental change in visual information processing under backward masking

Four-year-olds, eight-year-olds, and college students were compared with respect to their speed and strategy for processing form information in a pointing-recognition task. The target form arrays, varying in size from one to four forms, were presented tachistoscopically, followed by a masking array at varying intervals. No age differences in processing speed were found on single-item arrays, but four-year-olds were progressively slower as array size increased. A selective processing condition resulted in longer processing times for all Ss but was differentially more difficult for four-year-olds. Under the full report conditions, all Ss showed a parallel independent processing strategy as array size increased from one to two items, but four-year-olds did not apply this strategy as efficiently as older Ss. As array size increased from two to four items, only adults and eight-year-olds continued to show parallel independent processing, up to a limit. This age difference in processing strategv for the largest arrays may underlie age differences that have been found in short-term memory capacity.     

Recognition vs recall of visually vs acoustically confusable letter matrices

In an attempt to separate auditory and visual components in short-term memory, five subjects were exposed to letter matrices composed of six visually confusable letters, six acoustically confusable letters, or a mixture of the two, under two response conditions: recognition and recall. A 50-msec stimulus presentation was followed by a variable dark interval of 1, 250, 1,000, or 3,000 msec. In the recall condition, the interval was followed by a buzzer which signaled the subject to recall, in any order, as many letters as possible. In the recognition condition, the variable interval was followed by a second letter matrix which was either identical to the first matrix or differed from is by one letter. Subjects responded either "same" or "different." The results support the notion that the auditory component plays a major role in recall, whereas the visual component dominates in recognition.