Visual information processing of sequentially presented inputs: III. Further effects of list length and interstimulus interval values on sub-span storage and retrieval mechanisms

Two experiments were carried out, employing a computer-based cathode-ray tube display system, to study further the effects of sub-span Hst length, i.e., two, three, four, and five decimal digits, and relatively small interstimulus interval (ISI) values, i.e., 20, 40, 60, 80, and 100 msec, on visual information processing, storage, and retrieval mechanisms. The results of the first experiment confirmed the compttcated intenctions found in two earlier studies between Hst length and ISI values, but with much smaller ISI values than employed preriousfy. The results of the second experiment, in which unequal ISI values were employed within the same length input string, showed little effect resulting from this parameter, but it was suggested that a wider distribution of different ISI values within the same length input string would produce very strong effects.     

Differential payoff and locus of selectivity in a visual memory task

Two experiments were run to investigate the locus of selectivity in a visual memory task involving differential payoff for letters correctly recalled: Major variables consisted of value instructions given before or after the exposure of a display, the ratio of high to low value, and exposure duration. The results showed that Ss make more correct reports of higher value than of lesser value, whether value instructions are given before or after the display. Furthermore, overall performance and extent of selectivity increase with increasing exposure time, but more for the before than the after conditions of instruction. These results suggest that selectivity occurs both during perception and retention and during recall.     

Schematic concept formation: Feature measures and constraint redundancy as predictors

Constraint redundancy (R_c) was varied in order to manipulate the statistical structure of sets of patterns. Measures of pattern features and R_c were related to the categorization by Ss who had experienced different types of preexposure to sets of patterns from the same stimulus domain. Both R_c and pattern measures were related to the categories produced by Ss in a schematic-concept-formation (SCF) task.     

Psychophysical methodology IV: Phi gamma hypothesis and the method of limits

Assuming the phi-gamma hypothesis, deductions concerning the method of limits (ML) are derived. For a given step size, the selection of the initial stimulus for ascending series or for descending series has little effect on the summary statistical measures of the ML. Estimates of ML statistics are derived for different step sizes, and these estimates are used to estimate the mean and standard deviation of the phi-gamma hypothesis. Also considered are how summary statistical measures of the ML are influenced by extremely large and small step sizes and by the definition of a ML threshold.     

On the detectability of straight lines in visual noise: An extension of French’s paradigm into the millisecond domain

We report the results of a study that investigated the effects of four experimental parameters on the tachistoscopic detectability of dotted lines in a noisy background consisting of dynamic patterns of identical dots. Characteristics of the lines that were explored included dot spacing, dot numerosity, and line orientation. Dot spacing was shown to be the most powerful parameter in determining the masking effect: the closer the dots, the more easily the line was detected. Increasing the number of the dots was also effective in increasing the detectability of a line, but only up to a limit of five dots. The orientation of the line, on the other hand, did not alter its detectability. Increasing the density of the visual masking noise monotonically reduced the detectability of the line. These studies are an extension of French’s (1953, 1954) work, differing mainly in the fact that the stimulus material was presented tachistoscopically rather than in a mode that allowed prolonged (up to 5 sec) examination of the figures. Thus, they put the results in a domain in which physiological interpretations may be more critically evaluated. A comparison of the results suggests that essentially the same sorts of cognitive mechanisms are operating in the millisecond domain as in the longer exposures. This suggests that simple neurological models utilizing the concept of feature filters or detectors may be being prematurely applied to relatively complex perceptual processes.     

A Systems Dilemma

The current shift of interest, reflected in public policy, from the production of goods to the provision of services, has caused a major re-examination of the nature of the services the individual can expect from his society. This re-examination is producing a number of insights, some of them shocking. In particular, we are learning that many of the systems we have created to deliver services are, in the name of “progress” and “civilization,” contributing to the conditions of human distress they were designed to alleviate. Much has been written lately about how service systems of one kind or another subvert their announced goals—how a welfare system perpetuates poverty, or how the medical profession creates iatrogenic illness. There has not been very much written, however, about how several systems inadvertently combine in their day to day operations in such a way as to frustrate each others' activities, and how, in so doing, they destroy in varying degrees the lives of people, or render it difficult for them to improve their lives. We have all been much too tightly locked in our own niches by training, experience, and various types of private interest to see this kind of interlock. It comes into sharp perspective only when one studies the problems of a single person in terms of his total life space, his “ecology.” This paper represents an effort to describe one such situation in a family as viewed from a community health services program designed to approach human crises as ecological phenomena, and to explore and respond to them within this framework. We have found that the best way to organize our view of the environmental field people move in is according to the diverse systems which make it up, so we have labeled our theoretical base “ecological systems theory.” ( 1 ) What is of particular interest to the behavioral scientist in the situation described is that neither individual nor family diagnosis, nor the contributions of the larger systems (in this case a housing system and a system of medical care) will, if viewed separately, explain the state of the man in question. Only when the contributions of all of these systems are made clear, and their interrelationships explored, do the origins of the phenomena described begin to emerge.