Masking of alphabetic character recognition by dynamic visual noise (DVN)

The recognition of alphabetic characters composed of dot patterns is interfered with by dynamic visual noise (DVN) composed of similar dots randomly plotted over the character field. In this study we examine the general ability of the visual system to defect test characters as the level of this DVN varies. Three experiments are performed. The first deals with the effect of the DVN when the characters are embedded in continuous bursts of the noise, while the second and third examine the effects of leading and trading bursts of the DVN on character recognizability. Though the applicability of this paradigm to psychological questions is very brood, we concentrate on the problems of the channel capacity of the visual system and the persistence of the effects. The time course of the psychological instant is also considered.     

Masking of alphabetic character recognition by ultrahigh-density dynamic visual noise

In this paper the results of an experiment measuring the masking effects of ultrahigh-density dynamic visual noise (DVN) on character recognition are reported. It is shown that the period in which DVN acts as a mask is not extended beyond that measured with less dense DVN, even when the interval between the DVN dots is as small as 32 μsee. This result permits the rejection of the notion that there are sub threshold “tails” to the period of persistence of the visual store of the DVN dots. These results thus confirm the measurements made with less dense DVN of the duration of the period of persistence that allows confusion between sequential stimulus and mask dots to occur.     

Interaction of forward and backward visual masking

An investigation was conducted into the interaction of the forward and backward masking effects of unpatterned visual stimuli. It was found that detection of a test spot was easier under conditions that should have provided both forward and backward masking than under either forward masking or backward masking alone. The implications for an integration theory of masking are discussed, and the findings are contrasted with findings on the interaction of forward and backward masking by dynamic visual noise.     

Vibrotactile frequency recognition: forward and backward masking effects

Forward and backward vibrotactile recognition masking was investigated in 4 subjects with 240-Hz and 160-Hz targets of 20 ms duration and four 200-Hz masks, using interstimulus intervals (ISIs) ranging from -500 to 500 ms. Two of the masks (short) were 20 ms and two (long) were 200 ms in duration. One of each set of masks was matched in subjective intensity to the targets, but the others were more intense. The range of ISIs over which masking was obtained was comparable to that found by Massaro (1970) with auditory stimuli. Both short masks produced more masking than either long mask except at short ISIs. Larger mask intensities increased masking only at very short ISIs, and longer mask durations increased backward but not forward masking.     

Vowel recognition: Inferences from studies of forward and backward masking

The recognition of brief vowels was studied in forward and backward masking tasks. In a series of experiments in which both target and mask parameters were systematically varied, two populations of subjects were identified. The majority (Nonmaskers) evidenced little masking at any interstimulus interval, while relatively fewer subjects (Maskers) evidenced backward masking (but not forward masking) over a 100-200 ms interval. Increasing target set size systematically increased masking for the Maskers but not for the Nonmaskers. Adding white noise to the targets increased the extent of masking for both groups. These results suggest (1) that masking does not impose a substantive constraint on vowel perception in running speech, and (2) that multiple strategies may exist for vowel recognition.     

The speed of visual processing in children and adults: Effects of backward and forward masking

Children, 4-5 and 9-10 years old, and college-age adults were tested on two visual masking tasks. The first task required the Ss to identify whether a tachistoscopically presented bar was horizontal or vertical The second task, also using tachistoscopic presentation of stimuli, required Ss to locate a horizontal (or vertical) bar in a matrix of vertical (or horizontal) bars. In both tasks, backward masking produced greater disruption than did forward masking, and the amount of disruption induced by both backward and forward masking decreased as age increased. An Age by Masking Condition interaction was found only in the location task and reflected a much greater difference between backward- and forward-masking conditions for the youngest group than for the older groups. On the basis of these findings and other considerations, it was concluded that only in the location task, which presumably required visual search, was the speed of visual processing slower in the younger group.     

Age effects in backward visual masking (Crawford paradigm)

Fifteen Ss in each of four age groups (5-, 10-, 16-, and 22–23-years old) received backward visual masking. Group effects occurred at longer ISIs indicating slower prerecognition processing for younger Ss. In a second experiment 19-, 35-, and 55-year-old Ss were administered backward visual masking under the identical procedures of Exp. 1. The oldest Ss performed significantly worse than 19- and 35-year-old Ss, which did not differ significantly from each other. The general methodological features of both studies, as well as the obtained relationships were discussed.     

Orthographic and phonological computation in visual word recognition: Evidence from backward masking in Hebrew

We employed the backward masking paradigm to map the early computation involved in the perception of printed words in Hebrew. By independently manipulating orthographic and phonological overlap between targets and masks, we examined whether orthographic and phonological structure imposes late or early constraints on lexical access. The results demonstrated that the probability of reinstating a masked target depended on both the orthographic and the phonological overlap between the target and the mask. However, whereas phonemic structure seems to constrain lexical access only at short exposure durations, orthographic overlap also exerts its influence at longer durations.     

The effect of masker duration on forward and backward masking

Temporal masking of clicks by noise was investigated using forward and backward masking paradigms. Both the noise duration and the temporal separation, ΔT, between the click and noise were varied. For very brief ΔTs (100 microsec) and for very long ΔTs (100 msec), the duration of the masker did not greatly affect the click threshold. However, for intermediate ΔTs (3 msec), the threshold increased by as much as 44 dB as the noise duration increased from 0.1 to 100 msec. Temporal weighting functions, which describe the relative effectiveness of the noise as a function of ΔT, were computed from these data.     

U-shaped masking functions in visual backward masking: Effects of target configuration and retinal position

Printed letters were found to become increasingly susceptible to visual backward masking when presented to one side of the point of fixation: All masking was found to be a u-shaped function of the time interval separating the offset of the target from the onset of the masking figure. The interval at which maximum masking was observed, as well as the amount of masking observed, varied with the target-mask configuration studied. More masking was found when the ISI field was lighted than when it was not.     

Spatial effectiveness of the mask: Lateral inhibition in visual backward masking

Introducing a figure into a masking flash results in visual backward masking under conditions where a homogeneous masking flash does not suppress target detection. It is possible to analyze the spatial effects of such a masking figure in terms of lateral inhibition. It is hypothesized that incorporating a figure into the masking flash changes the inhibitory pattern the mask produces in the visual system. The interaction between the firing pattern produced by the mask and the residual inhibition from the preceding target presentation results in a phenomenal representation different from that produced by either the target or the mask alone.     

The crossmodal facilitation of visual object representations by sound: evidence from the backward masking paradigm

We report a series of experiments designed to demonstrate that the presentation of a sound can facilitate the identification of a concomitantly presented visual target letter in the backward masking paradigm. Two visual letters, serving as the target and its mask, were presented successively at various interstimulus intervals (ISIs). The results demonstrate that the crossmodal facilitation of participants' visual identification performance elicited by the presentation of a simultaneous sound occurs over a very narrow range of ISIs. This critical time-window lies just beyond the interval needed for participants to differentiate the target and mask as constituting two distinct perceptual events (Experiment 1) and can be dissociated from any facilitation elicited by making the visual target physically brighter (Experiment 2). When the sound is presented at the same time as the mask, a facilitatory, rather than an inhibitory effect on visual target identification performance is still observed (Experiment 3). We further demonstrate that the crossmodal facilitation of the visual target by the sound depends on the establishment of a reliable temporally coincident relationship between the two stimuli (Experiment 4); however, by contrast, spatial coincidence is not necessary (Experiment 5). We suggest that when visual and auditory stimuli are always presented synchronously, a better-consolidated object representation is likely to be constructed (than that resulting from unimodal visual stimulation).     

Effects of test-mask similarity on forward and backward masking of patterns by patterns

Summary Effects of test-mask similarity on the masking function were examined in two experiments. In Experiment 1, random bar patterns were used as test and mask stimuli. Bars were oriented in 135° oblique direction in test stimuli, and in 135° or 45° oblique direction in mask stimuli. The SOA was varied from 0 to 100 ms (backward masking). In Experiment 2, red and blue random dot patterns were used as both test and mask stimuli, with SOAs of –100 to 100 ms (forward and backward masking). The subject was asked to report the number of bars or dots as quickly as possible. The results of four subjects in one experiment and five in the other indicated that masking effects were generally greater when the test and mask stimuli were the same in orientation or color than when they were different. Slightly asymmetrical U-shaped functions were obtained both in the same and in different (orientation or color) conditions. A two-factor model with a similarity-related symmetrical integration process and a similarity-unrelated asymmetrical interuption process was considered.Experiment 1 was conducted by the first and third authors at Chiba University, and Experiment 2 was performed by the first and second authors at the University of Tokyo     

The influence of forward and backward associative strength on false recognition

In an experiment, I examined the influence of 2 associative factors on false memory in the Deese-Roediger-McDermott paradigm (Deese, 1959; Roediger & McDermott, 1995): the strength of the association from studied items to unstudied lure items (backward associative strength, or BAS) and the strength of the association from unstudied lure items to studied items (forward associative strength, or FAS). BAS and FAS were manipulated, and participants were asked to respond rapidly at retrieval or were allowed to respond in a self-paced manner in order to examine the contributions of automatic and controlled memory processes to lure errors. The results of this study demonstrated that both BAS and FAS influenced lure errors under speeded retrieval conditions and under self-paced retrieval conditions, as well as that lure errors generally increased when retrieval time increased. These results favor the explanation of false memory offered by global-matching models over those of activation-monitoring theory and fuzzy-trace theory.     

Recent models and findings in visual backward masking: a comparison, review, and update

Visual backward masking not only is an empirically rich and theoretically interesting phenomenon but also has found increasing application as a powerful methodological tool in studies of visual information processing and as a useful instrument for investigating visual function in a variety of specific subject populations. Since the dual-channel, sustained-transient approach to visual masking was introduced about two decades ago, several new models of backward masking and metacontrast have been proposed as alternative approaches to visual masking. In this article, we outline, review, and evaluate three such approaches: an extension of the dual-channel approach as realized in the neural network model of retino-cortical dynamics (Ogmen, 1993), the perceptual retouch theory (Bachmann, 1984, 1994), and the boundary contour system (Francis, 1997; Grossberg & Mingolla, 1985b). Recent psychophysical and electrophysiological findings relevant to backward masking are reviewed and, whenever possible, are related to the aforementioned models. Besides noting the positive aspects of these models, we also list their problems and suggest changes that may improve them and experiments that can empirically test them.