Backward Pattern Masking Research Articles

Psychophysical "blinding" methods reveal a functional hierarchy of unconscious visual processing.

Numerous non-invasive experimental "blinding" methods exist for suppressing the phenomenal awareness of visual stimuli. Not all of these suppressive methods occur at, and thus index, the same level of unconscious visual processing. This suggests that a functional hierarchy of unconscious visual processing can in principle be established. The empirical results of extant studies that have used a number of different methods and additional reasonable theoretical considerations suggest the following tentative hierarchy. At the highest levels in this hierarchy is unconscious processing indexed by object-substitution masking. The functional levels indexed by crowding, the attentional blink (and other attentional blinding methods), backward pattern masking, metacontrast masking, continuous flash suppression, sandwich masking, and single-flash interocular suppression, fall at progressively lower levels, while unconscious processing at the lowest levels is indexed by eye-based binocular-rivalry suppression. Although unconscious processing levels indexed by additional blinding methods is yet to be determined, a tentative placement at lower levels in the hierarchy is also given for unconscious processing indexed by Troxler fading and adaptation-induced blindness, and at higher levels in the hierarchy indexed by attentional blinding effects in addition to the level indexed by the attentional blink. The full mapping of levels in the functional hierarchy onto cortical activation sites and levels is yet to be determined. The existence of such a hierarchy bears importantly on the search for, and the distinctions between, neural correlates of conscious and unconscious vision.

Perceptual identification across the life span: a dissociation of early gains and late losses

The age-correlated gains and losses in visual identification under backward pattern masking were studied in a representative sample of 226 individuals ranging from 6 to 88 years of age. Participants identified masked symbols at leisure under high and low stimulus quality and at varying Stimulus Onset Asynchronies. Performance increased from childhood to early adulthood and then decreased, describing the common inverted U-shaped function. However, measures of general processing speed accounted for the gains in childhood and adolescence but not for losses in older age. This asymmetry between child development and aging is inconsistent with general-factor lifespan theories of cognitive development and suggests that specific mechanisms underlying visual identification during child development and aging are different.

Visual attention and the mechanism of metacontrast

The U-shaped metacontrast function may result from the superimposition of two monotonic components which reflect the effects of mechanisms similar to the peripheral and central processes suggested for backward pattern masking by Turvey (Psychol Rev 80:1-52, 1973). In an experiment using the disc-ring paradigm, it was demonstrated that the decreasing and increasing branches of the metacontrast function are differently affected by the exposure duration of the mask and a task-irrelevant stimulus (distractor) appearing in the contralateral visual hemifield. The phenomenal representation of masking is different for the two parts of the curve. It is suggested that masking in the second part of the masking function, but not in the first, is related to the control of visual attention.

Perceptual learning in visual backward pattern masking.

The present study examined the practice effect of backward pattern masking in the context of recent researches on perceptual learning. On the discrimination task, thresholds decreased substantially with practice. In addition, the practice effect was specific to the mask pattern. In contrast, it cannot reasonably be assumed that the practice effect was specific to the eye and the retinal position. These findings suggest that practice diminished the interruption of processing in capacity-limited processing. In addition, the specificity of the practice effect to the mask pattern suggests that participants learned to filter out the specific type of mask from capacity-limited processing. On the detection task, thresholds decreased with practice. But the improvement was smaller on the detection task than on the discrimination task. It may be assumed that the practice effect on the detection task does not involve a decrease in the effect of the interruption in capacity-limited processing.

Modulation of backward pattern masking by focal visual attention

The effect of focal visual attention on backward pattern masking was investigated using an orientation discrimination task. The results show that attention reduces primarily the effect of interruption masking, the later component of pattern masking, which occurs when the delay between the target and mask onset is about 50-150 ms. The strongest spatial cueing effect, i.e. the strongest reduction of the orientation discrimination threshold due to focal attention, was observed at intermediate (approximately 100 ms) target-to-mask stimulus onset asynchrony (SOA). There was a weak effect of cueing at shorter SOAs, and no or a very weak attentional effect was present at longer target-to-mask SOAs, where the pattern masking effect is absent. The dynamics of attentional modulation of backward pattern masking correlates closely with the dynamics of the attentional modulation of neuronal responses in the early visual cortex.

Backward Pattern Masking of Familiar and Unfamiliar Materials in Disabled and Normal Readers

A discrimination task involving backward pattern masking was designed to investigate differences between disabled and normal readers in text perception. Masking was observed for both groups with unfamiliar Japanese materials, but disabled readers were less sensitive in discriminating than were normal readers. The same result was obtained with Roman letters, despite the high familiarity of materials to both groups, and with nonwords and words. A significant interaction between group and stimulus onset asynchrony, indicating that disabled readers recovered from masking at a slower rate than normal readers, was found only with nonwords. Visual factors alone could not have mediated group differences. A subgroup of disabled readers, formed on the basis of susceptiblity to masking, showed evidence of a deficit in rate of visual processing. The results are likely due to differences in the quality of representations of visual information used in discrimination and in word recognition.

Effects of car window tinting on visual performance: a comparison of elderly and young drivers

A major concern in allowing the tinting of car front side windows to 35% visible light transmittance (VLT) is that tasks performed through these windows often require the rapid detection of low-contrast, unilluminated targets. If the tinting interferes with detection of targets then road safety may be compromized. Speed of cognitive and visual processing declines with age; performance on backward pattern masking tasks can indicate this slowing in processing speed. Two experiments compared performance of the young and elderly adult on two backward pattern masking tasks with levels of VLT from 100 to 20%. The first experiment found a decrement in performance for the elderly at 63% VLT and for all participants at 20% VLT. The second experiment found a decrement in performance for the elderly at 35% VLT. It was concluded that road safety may be compromized if the front side windows of cars are tinted to 35% VLT.

Interpreting inspection time as a measure of the speed of sensory processing

White (1993) provided a number of theoretical reasons to justify the replacement of the original inspection time (IT) rationale (Vickers, Nettelbeck & Willson, 1972) which locates the IT delay at the postsensory level, by the integration theory of backward pattern masking which locates the IT delay at the sensory level. This theoretical paper explores the consequences of adopting a sensory theory of IT. Two similarities between the sensory and post-sensory theories are described; and six implications of adopting the sensory approach are discussed. The similarities are that both theories view IT as a measure of the speed of making figural discriminations independent of differences in the ability to deploy attention or to adopt particular cognitive strategies; and that both see the exploitation of apparent movement/flicker cues as a challenge to the validity of IT measures. The first implication of adopting the sensory theory is that IT must now be seen as a measure of the speed of making sequential discriminations between the target and mask, rather than simultaneous discriminations between the alternative targets. The second and third are that the use of only two alternative targets, and the use of an accuracy criterion of 100% (or similar), should be seen as arbitrary restrictions. The fourth is that the existence is to be expected of small positive SOAs at which chance levels of performance are obtained. The fifth is that the backward masking procedure should be seen as only one of two very different procedures that can be used to measure ‘integration time’ —The other being the ‘form integration’ procedure. The sixth is that, because integration times are measures of ‘processing speed’, the form integration and backward masking tasks should prove to be useful tools for the investigation of aging and psychometric intelligence.

Visual Dysfunction Predicts Cognitive Deficits in Alzheimer??s Disease

Deficits in basic visual capacities are prevalent in Alzheimer's disease (AD), raising the question of their impact on cognitive function. We examined the relation between vision and cognition in 72 patients with AD. Vision tests assessed color discrimination, stereoacuity, contrast sensitivity, and backward pattern masking. For cognitive tests of object recognition, at least 25% (up to 50%) of score variance was predicted by performance on a vision test. For tests of spatial localization, only 2 to 11% of the variance was predicted by performance on a vision test. The results indicated that: (1) visual dysfunction was a significant predictor of cognitive dysfunction in AD, and (2) visual deficits in AD may have a strong functional impact on performance in specific cognitive domains.

Prevalence of visual deficits in Alzheimer's disease.

This study addressed the issue of prevalence and pattern of visual deficits in 77 subjects with Alzheimer's disease (AD) and 111 healthy control subjects. We defined cutoff scores that would be expected from only 1 control subject of 100 (p = 0.01). The percentage of AD subjects who performed at or worse than this level varied across the 16 visual tests from a high of 58% to a low of 0%. The distribution of impairment across tests suggests a high vulnerability in AD of pattern vision, moderate vulnerability of spatial vision, and low vulnerability of motion and flicker perception. We found evidence for heterogeneity in the AD subject group: a subgroup (N = 14) emerged that was characterized by poor performance on the Backward Pattern Masking test, relatively young age, and relatively short duration of AD. Overall, the results indicate that visual dysfunction, especially on Backward Masking, is a common sign of AD.

Theoretical implications of the mnemonic benefits of perceptual interference.

How should interfering with the perception of items during study affect memory for those items? Recent research by Nairne (1988) and Hirshman and Mulligan (1991) has demonstrated that backward pattern masking during study enhances later memory. This article examines whether traditional explanations of encoding benefits, including rehearsal, visual distinctiveness, and encoding effort, can account for this result. No evidence was found for any of these hypotheses. An explanation that focuses on the compensatory processing of higher level perceptual representations is proposed. This explanation provides a plausible explanation of the results of 7 experiments. The article concludes with a discussion of the implications of the explanation for perceptual priming and other manipulations of perceptual interference. How does interfering with the perception of items during study affect memory for those items? Nairne (1988) and Hirshman and Mulligan (1991) recently investigated this question using visual masking. These investigators examined memory performance on items presented in two study conditions. In the control or intact condition items were presented for 2.5 s. In the experimental or interference condition items were presented briefly (i.e., 100 ms) and then followed with a backward pattern mask (i.e., a row of Xs) presented for 2.4 s. The mask obscures the visual features of the study item, interfering with its perception. Surprisingly, these studies have demonstrated that interfering with perception using visual masking can actually improve memory performance. Nairne (1988) reported an advantage for the interference condition in recognition memory. Hirshman and Mulligan (1991) replicated Nairne's recognition memory results and demonstrated that this effect also occurs in free recall.1 These results seem surprising from several perspectives. First, many classical (Atkinson & Shiffrin, 1968; Waugh &

Susceptibility to Type A backward pattern masking among hypothetically psychosis-prone college students.

Susceptibility to Type A backward pattern masking among hypothetically psychosis-prone college students.

Susceptibility to type A backward pattern masking among hypothetically psychosis-prone college students.

Susceptibility to type A backward pattern masking among hypothetically psychosis-prone college students.

Role of contrast, lettercase, and viewing conditions in a lateralized word-naming task.

Because of the asymmetric functional organization of the brain, the process of naming a visually presented word necessarily engages, in its end stage, the structures of the left anterior hemisphere, forcing information received by the right hemisphere to be transferred across the corpus callosum. On the basis of this functional organization, a task requiring speeded naming of a laterally presented word was designed to examine the nature of the information transferred from the right to the left hemisphere and the type of process initially performed by the right hemisphere before transfer. Three categories of variables, each affecting particular components of the stimulus were manipulated in a within-subject design: (1) the viewing conditions, with the target word presented under flicker masking, which desensitizes the transient low-frequency channels while increasing the sensitivity of the low-frequency sustained channels, with backward pattern masking, which interferes with the integration of high spatial frequencies, or without masking; (2) the contrast of the word stimulus, which determines stimulus energy; and (3) the lettercases, which influence the relative salience of the component and configural properties of the word. Analysis of latencies showed a right-visual-field main effect and interactions between visual field and contrast and between visual field and lettercase. Right visual field superiority increased with a reduction in stimulus energy, and the right hemisphere benefited more than the left hemisphere from the additional information provided by the configural property of the lowercase word. The viewing conditions influenced the strength of these effects but did not modify their general pattern. The results are discussed with respect to interhemispheric transfer of visual information and the processing competence of the cerebral hemispheres.

Backward pattern masking can vary as a nonmonotonic function of target duration: on the influence of intratraget metacontrast.

The magnitude of backward masking is usually found to vary inversely with the amount of information about a target that is made available to the visual system. Contrary to these findings, we report a nonmonotonic relation between the magnitude of backward pattern masking and target duration. Specifically, masking decreased as target duration was increased to about 8 msec and, then, became more severe as target duration was further increased to a value of at least 40 msec. The occurrence of the nonmonotonic function depended on (a) the degree of definition of the target's edges, (b) the luminance levels within the target stimulus, and (c) the state of adaptation of the eye. It is hypothesized that the source of the nonmonotonic function was metacontrast interference that originated from within the target stimulus configuration. This hypothesis was supported by data that indicated that in the absence of any mask presentations, the apparent contrast between the target and its immediate background varied as a nonmonotonic function of target duration.

Backward pattern masking can vary as a nonmonotonic function of target duration: On the influence of intratarget metacontrast.

Backward pattern masking can vary as a nonmonotonic function of target duration: On the influence of intratarget metacontrast.

Predictions of U-Shaped Backward Pattern Masking from Considerations of the Spatio-Temporal Frequency Response

The threshold detectability of a briefly presented target stimulus consisting of a vertical sinusoidal grating was affected not only by the spatial frequency content of an equally briefly presented, two-octave-wide masking noise, but also by the time interval separating the onsets of the target and its mask. Over a range of stimulus onset asynchronies, in which the mask onset either preceded, coincided with, or followed the target onset, a mask with a low spatial frequency content had its greatest masking effect on a high spatial frequency target grating when the mask followed the target by 120–180 ms. When the mask had a high spatial frequency content and the target was of low spatial frequency, or when the target was entered on the mask frequency band, optimal masking effects occurred when the onsets of the mask and target coincided. The results are discussed in relation to previous masking studies, particuarly those in which U-shaped backward pattern masking functions are obtained.

Conduction velocity in pathways from retina to superior colliculus in the cat: a correlation with receptive-field properties.

Conduction velocity in pathways from retina to superior colliculus in the cat: a correlation with receptive-field properties.