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.