The psychophysical inquiry into binocular summation

Experiments that compare monocular and binocular visual performance of human psychophysical Os on a variety of visual tasks are reviewed. The review attempts to include all experiments published in English in this century, excluding work on stereopsis, rivalry, and evoked potentials. The concept of probability summation as a baseline for assessing the presence of neural summation is discussed, and the assumptions of several models for estimating probability summation are considered. Experiments are classified in terms of visual task, major categories being increment detection, flicker fusion, brightness magnitude, and contour resolution. A major conclusion is that binocular performance is superior for essentially all task categories and in most cases by a magnitude greater than that predicted by appropriate probability summation models.     

Increment detection thresholds during binocular rivalry suppression

In two experiments, two-choice forced-choice duration thresholds for increment test flashes were estimated during phases of rivalry suppression and nonsuppression and for a nonrivalry monocular control condition. In both experiments thresholds of both eyes of each S were measured and, to maximize correct detections, feedback was given after every trial and Ss were relieved of the task of continually reporting changes in rivalry phases. Results of both experiments support the conclusion that suppression constitutes an elevation in threshold, on the order of .5 log units relative to thresholds found during nonsuppression and monocular conditions. These data, in concert with others, reinforce the general conclusion that rivalry suppression is an inhibitory state that nonselectively attenuates all classes of inputs falling within the spatial boundaries of the suppressed target.     

The sense-making approach for audience assessment of adolescents

The purpose of the research was to test the methodology used to identify how adolescents approach their nutrition concerns and questions. The methodology was based on Dervin's sense-making theory. Using a time-line interview technique, 305 adolescents 14 to 16 years of age detailed a situation involving their most important nutrition concerns. Other pertinent information was obtained. Cluster analysis was chosen as the appropriate analysis to identify groups of adolescents who responded similarly to the technique. Discriminant analysis was then used to determine which variables maximally separated the groups. Four groups were identified, two of which described action-oriented approaches to dealing with nutrition situations and differed in terms of how much outside help they wanted. The remaining two groups perceived barriers to dealing with situations and also differed in how much help they wanted. A fifth group indicated no nutrition concerns or questions. The results will be used to develop and test the effectiveness of nutrition education when it is focused on the different approaches.     

Binocular detection of positive and negative flashes

Binocular forced-choice detection rates were measured under conditions where both eyes received positive flashes, both eyes received negative flashes, and one eye received a positive flash while the other received a negative flash. When both eyes received the same kind of flash, both positive or both negative, detection rates were,greater than probability summation. When one eye received a positive flash while the other received a negative flash, detection rates were near a level expected on the basis of probability summation. It is concluded that, at the level of forced-choice detection. positive and negative flashes are detected as though they were separate, independent events.     

Free association,free recall,and stimulated recall compared

Three primary methods of recall (free association, free recall, stimulated recall) and two modifications of them (modified free association, modified stimulated recall) were defined by use of three variables: (a) presence or absence of prior laboratory training, (b) presence or absence of E controlled test stimulation, and (c) test instructions to free associate or to recall Data obtained from approximately 300 Ss and an earlier set of 600 revealed the differential effectiveness of all three primary methods in recall and misrecall.