Biomedical subjects

Vincent Di Lollo

Publications and source records attributed to Vincent Di Lollo.

9 recordsLinked to original sources

PubMed1992

Inverse duration effects in partial report.

In partial-report experiments, an array of stimuli is displayed briefly, followed by a probe indicating the items to be reported. When exposure duration of the array is increased, 2 contrasting outcomes have been found: Some experiments find that performance improves (direct-duration effect); others find that it deteriorates (inverse-duration effect). The objective here was to identify the reasons for the discrepant results. This was done by investigating the roles played by 5 factors that differed between the 2 sets of contrasting studies. An inverse-duration effect was obtained in each of 6 experiments; its magnitude was affected by retinal eccentricity and by the number of items denoted by the probe. The effect was independent of array configuration and of number of items in the array. The direct-duration effect was shown to arise from a confounding of exposure duration and brightness.

Adult↗

PubMed1990

On the relation between metacontrast masking and suppression of visible persistence.

Does the introduction of additional contours in a display sequence (an operation known to reduce the strength of suppression in metacontrast) also reduce suppression of visible persistence? In three experiments, duration of visible persistence was estimated by a method in which successful performance depends on the temporal integration of a pattern whose elements are displayed in two successive frames. In this procedure, the arrival of the trailing frame is known to exert a suppressive influence on the visible persistence of the leading frame. Embedding the elements of the leading frame within additional contours (a line grid) reduced the degree of suppression exerted by the trailing frame. This did not occur when the grid was part of the trailing display. We conclude that suppression of visible persistence and metacontrast masking belong to the same class of events.

Adult↗

PubMed1988

Two forms of persistence in visual information processing.

Iconic memory, which was initially regarded as a unitary phenomenon, has since been subdivided into several components. In the present work we examined the joint effects of two such components (visible persistence and the visual analog representation) on performance in a partial report task. The display consisted of 15 alphabetic characters arranged around the perimeter of an imaginary circle on the face of an oscilloscope. The observer named the character singled out by a bar-probe. Two factors were varied: exposure duration of the array (10, 50, 100, 150, 200, 300, 400 or 500 ms) and duration of blank period (interstimulus interval, ISI) between the termination of the array and the onset of the probe (0, 50, 100, 150, or 200 ms). Performance was progressively impaired as both exposure duration and ISI were increased. The results were explained in terms of a probabilistic combinatorial model in which the timecourses of visible persistence and of the visual analog representation are regarded as time-locked to the onset and to the end of stimulation, respectively. The impairing effect of exposure duration was attributed to the relatively high spatial demands of the task that could be met optimally by information in visible persistence (which declines as a function of exposure duration), but less adequately by information in the visual analog representation. A second experiment, employing a task with lesser spatial demands, confirmed this interpretation.

Afterimage↗

PubMed1985

Suppression of visible persistence.

Five experiments were conducted to examine duration of visible persistence in sequences of stimuli. The basic display consisted of a point that stepped around a circular path on the face of an oscilloscope. Observers estimated the number of points seen simultaneously. Results were compared with a control condition in which the points were plotted in random order rather than sequentially. It was found that visible persistence of a point is suppressed if other points are shown nearby and after an appropriate delay. The degree of suppression depended on the spatial proximity of successive points. It was also found that both duration of visible persistence and degree of suppression increase with eccentricity in the visual field. The results are discussed in terms of two independent processes, persistence and suppression, that operate in a hierarchically antithetical relation.

Figural Aftereffect↗

PubMed1984

On the relationship between stimulus intensity and duration of visible persistence.

Stimulus intensity and duration of visible persistence have been found to vary directly in some studies but inversely in others. Hawkins and Shulman (1979) have proposed that this inconsistency can be resolved by separating the studies that employed a decrement-threshold measure of persistence (Type I measure) from those that measured the total duration of persistence (Type II measure). They suggested that Type I measures yield an inverse relationship, whereas Type II measures yield a direct relationship between intensity and persistence. Hawkins and Shulman's model is incomplete in ways that are easily remedied. However, the model is totally contradicted by the experimental evidence. A new resolution of the inconsistent results is proposed in terms of retinal afterimages.

Attention↗

PubMed1983

Initial stages of visual information processing in dyslexia.

Four experimental tasks were employed to explore the initial stages of visual information processing in a group of dyslexic boys and in a group of normal control subjects ranging in age from 8 to 14 years. Two tasks involved visual backward masking; the other two were temporal integration tasks. The backward-masking tasks yielded evidence of slower rates of visual information processing in dyslexic children; the temporal-integration tasks yielded evidence of longer duration of visible persistence in dyslexic children. This effect was most evident in situations in which sequential stimuli impinged on the same retinal location. Some age trends in the development of these effects are noted. It is suggested that the dyslexic visual system may take an unusually long period of time to recover from the aftereffects of neural activity evoked by an inducing stimulus.

Adolescent↗

PubMed1982

Age-related changes in rate of visual information processing.

Each of four groups of 12 subjects performed four psychophysical tasks. The age ranges of the four groups were 19-31, 45-57, 58-70, and 71-83 years, respectively. All four tasks required some form of visual information processing: Two were backward-masking tasks; two were temporal-integration tasks. In all four tasks increasing temporal functions over age were obtained, suggesting slower processing rates as age increased. The results support an active processing model of visual perception that interprets duration of visible persistence and duration of interval in which backward masking is effective as indices of the time course of early stages in the processing of stimulus features. The evidences also suggests that backward masking and visible persistence may be mediated by distinct mechanisms that are affected differently by aging processes. A model that conceptualizes the visual system as a multichannel processor is proposed as an explanation for some of the findings.

Adult↗

PubMed1981

Duration of visible persistence in relation to range of spatial frequencies.

Five experiments examined the relationship between range of spatial frequencies contained in a visual display and duration of visible persistence. The high spatial frequency contents of the display were reduced by defocusing the image at the retina. Duration of visible persistence was measured by a task that required perceptual integration of a pattern whose parts were displayed sequentially in time. Experiments 1 and 2 showed that progressive reductions in the high-frequency contents of the display produced corresponding decrements in the duration of visible persistence. Experiments 3, 4, 5 showed that decrements in the duration of visible persistence could not be attributed to changes in the apparent size or in the brightness of the display brought about by defocusing. The results were interpreted in terms of the temporal response properties of perceptual mechanisms attuned to separate ranges of spatial frequencies. Strong parallels were drawn with the multichannel theory of visual information processing proposed by Breitmeyer and Ganz.

Discrimination Learning↗

PubMed1980

Temporal integration in visual memory.

Iconic memory has often been likened to a sensory store whose contents drain away rapidly as soon as the inducing stimulus is turned off. Instances of short-lived visible persistence have been explained in terms of the decaying contents of iconic store. A fundamental requirement of this storage model is that strength of persistence should be a decreasing function of time elapsed since the cessation--not since the onset--of the inducing stimulation. That is, strength of visible persistence may be directly related--but not inversely related--to the duration of the inducing stimulus. Two complementary paradigms were utilized in the present studies. In the first paradigm performance was facilitated by visible persistence in that the task required the bridging of a temporal gap between two successive displays. In the second paradigm (forward visual masking by pattern), performance was impaired lingering visible persistence of the temporally leading mask. Both paradigms yielded evidence of an inverse relationship between duration of inducing stimulus and duration of visible persistence. More specifically, in a task requiring temporal integration of a pattern displayed briefly in two successive portions, performance was severely impaired if the duration of the leading part exceeded about 100 msec. This suggests an inverse relationship between duration of inducing stimulus and duration of sensory persistence and allows the inference that visual persistence may be identified more fittingly with ongoing neural processes than with the decaying contents of an iconic store. In keeping with this suggestion, two experiments disconfirmed the conjecture that lack of temporal integration following long induced stimuli could be ascribed to emergence of unitary form separately in the two portions of the display or to the triggering of some sort of discontinuity detection mechanism within the visual system. In added support of a "processing" model, two further studies showed that the severity of forward masking by pattern declines sharply as the duration of the leading mask is increased. This pattern of results is equally unsupportive of a storage theory of iconic persistence as a perceptual moment theory in any of its versions. This is so because both theories regard interstimulus interval rather than stimulus-onset asynchrony as the crucial factor in temporal integration. Neither can the results be explained in terms of receptor adaptation or of metacontrast suppression. The theory of inhibitory channel interactions can encompass the more prominent aspects of the results but fails to account for foveal suppression and for some crucial temporal effects.

Discrimination Learning↗