The dark-interval threshold as a function of age

Abstract

The threshold for the dark interval between two flaslles was illl'estigated ill 100 elementary school children, age 6-IU. It was foulld that Ille threshold decreased with chrollological age, 'a findillg altribllted to physiological agillg of Ille I'isual receptor system producillg diminished persistence of tile illitial stimulus.Pollack (\ 968) has put forth a two-process theory to ex plain age changrs in visual perception_ One of these processes. nondevelopmental in nature. involves a progressive loss in receptor sensitivity due to physiological aging_ The other process is "developmental" in that age changes are related to central cognitive functions and abilities which are hierarchically organized. Within the framework of this theory, those phenomena which show non developmental age changes (Type I) are not correlated with intellectual ability. but appear to be related directly to receptor efficiency and various stimulus variables such as intensity, duration, contrast, and orientation. Those phenomena showing developmental age changes (Type II) are correlated with intellectual ability and do not depend as much upon classical stimulus variation. Presentation of such phenomena usually involves a sequence of discrete stimulus events, registered by the S as traces, which are then centrally compared and contrasted.It is assumed that in making judgments about two stimuli presented in rapid succession, the individual early in life makes use of the physical persistence of the initial stimulus to make what is virtually a simultaneous comparison. As this stimulus persistence weakens as a function of aging in the receptor system, comparison comes to be based upon the higher-order cognitive function of comparing the trace of the vanished initial stimulus ...,ith the second stimulus. This transition was demonstrated by Pollack (1966) in a study dealing with apparent movement. The temporal range of apparent movement decreased between the ages of 6 and 9, but increased again beyond the age of 9. Correlation with IQ was nonsignificant for the 6-to 9-year-olds, but positive and significant for the 10-and Il-year-olds. The pattern of results obtained in this experiment was very similar to that obtained in an earlier study by Pollack (1960), concerning the frequency of occurrence of figural aftereffects following brief inspection.The present experiment was designed to test further the hypothesis that stimulus persistence declines with age. The dark-interval threshold (Din can be thought of as a simplified version of the critical flicker frequency (CFF), in which two flashes of light are presented in quick temporal succession with a varying interflash interval. The S is simply asked to report whether he can detect a dark interval between the flashes. At the present time, data on the DIT are very scarce. In general, results from studies of CFF have shown a decrease in CFF (poorer performance) beyond the age of 14. Cross (1963) performed a study of CFF with an age range of 6 to 12 years. She found a significant increase in CFF (bet...

The effects of age and intelligence on the dark-interval threshold

“…The flash intensity level used was 8.84 ft-c, as measured by a Macbeth Illuminometer at the eyepiece. A preliminary experiment (Pollack, Carter, & Ptashne, 1968) had shown no differences due to brightness. It was decided, therefore, to use the maximum brightness permitted by the tachistoscope.…”

Cross-cultural study of age-related differences in perceptual acuity.

“…Piaget (1961) has attributed the reduction in susceptibility to illusions such as the verticalhorizontal (Type I illusion) to the growing child's improved ability to direct and hence decenter his attention in any visual display. The increase in susceptibility to Type II illusions (e.g., the Ponzo illusion) may have something to do with a decline in the efficiency of the visual system (Pollack, Ptashne, & Carter, 1968).…”