Metacontrast

Alpern, Mathew

doi:10.1364/josa.43.000648

Cited by 337 publications

(244 citation statements)

References 16 publications

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“…The first ingredient in the sensory explanation, then, is that spaces are more effective in the periphery. Alpern (1953) postulated that there was increased contour interaction in the periphery. A space in the periphery, then.…”

Section: Resultsmentioning

confidence: 99%

Lateral masking in visual information processing

Wolford

Hollingsworth

1974

Perception & Psychophysics

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When unrelated letter strings are presented tachistoscopically, the end letters are reported more often than their neighbors; and when spaces are inserted into strings, performance on certain adjacent letters is superior to performance on those letters when no spaces were present. An experiment was conducted to determine the nature of those spacing effects. Letter strings were presented at a variety of retinal locations, and spaces were inserted into different positions in the instructed left-right processing order. The space effect was unrelated to processing order, but it was dependent on retinal location. To account for the various asymmetries, it was necessary to postulate that letters tend to interact with adjacent letters and that the interaction was not spatially symmetric. Furthermore, it was found that spaces had greater effects on "right-hand" letters than on symmetric letters. It was therefore concluded that letters interact at the feature level.When a string of letters is presented tachistoscopically in the right visual field (RVF), the probability of identifying one of the letters as a function of serial position is usually U-shaped (see, e.g., Estes & Wolford, 1971). Variables which contribute to the correct identification of a letter include retinal location, report order, and the number and position of surrounding letters. The space following the last letter is of particular interest as none of the other three variables predict an upturn at the end of a string in the RVF. Compared to the penultimate letter, the last letter is both further from the center of the fovea and later in the instructed processing and report orders. It is possible that the last letter is aided by the absence of contour interaction on one of its sides.There is evidence in the literature that the presence of a space in a string can have a marked effect on performance. Shaw (1969) introduced spaces into the middle of letter strings and found that a space which followed a letter in the instructed processing order (postspace) increased performance on that letter. A prespace, however, had little or no effect on the identification of that letter. A question of some importance in the understanding of visual information processing is whether that space effect is sensory in nature (due to lessened contour interaction) or cognitive (based on considerations of processing and memory). Shaw asserted that the asymmetry .The project reported herein was performed pursuant to a grant from the U.S. Office of Education, Department of Health, Education and Welfare. The opinions expressed herein, however, do not necessarily reflect the position or policy of the U.S. Office of Education, and no official endorsement by the U.S. Office of Education should be inferred. This article was written while the senior author was visiting the Center for Human Information Processing at the University of California, San Diego, The center (under partial support from NIMH Grant MH-15828) was generous in its assistance. implied a cognitive effect because of its...

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Section: Resultsmentioning

confidence: 99%

Lateral masking in visual information processing

Wolford

Hollingsworth

1974

Perception & Psychophysics

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“…As set size is increased, the mask representation is assumed to become stronger whereas the target representation remains the same. We believe this modeling of attention to be inappropriate.It has long been known that the strength of metacontrast masking is directly related to mask intensity (Alpern, 1953). It is, therefore, unsurprising that weakening the mask reduces the metacontrast effect in all extant models.…”

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confidence: 99%

Object substitution without reentry?

Lollo

Enns

Rensink

2002

Journal of Experimental Psychology: General

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(2002) used computer simulations to claim that many current models of metacontrast masking can account for the findings of V. Di Lollo, J. T. Enns, and R. A. Rensink (2000). They also claimed that notions of reentrant processing are not necessary because all of V. Di Lollo et al. 's data can be explained by feed-forward models. The authors show that G. Francis and F. Hermens's claims are vitiated by inappropriate modeling of attention and by ignoring important aspects of V. Di Lollo et al. 's results.We note with interest Francis and Hermens's (2002) article, which purports to show that the findings reported by Di Lollo, Enns, and Rensink (2000) can be explained by other models of metacontrast masking. To buttress their claim, Francis and Hermens reported computer simulations showing that some of our results can be modeled by the theories of Bridgeman (1978), Francis (2000) and Weisstein (1968). This claim has a good deal of surface appeal because it is parsimonious. It argues that our results can be explained without recourse to the new concept of object substitution. Parsimony, however, is achieved at the cost of inappropriate modeling of attention and modeling an incomplete portion of our masking data. Here, we reiterate our original claim that reentrant modeling is necessary for explaining our findings. We do so by showing that a plausible case for the sufficiency of feed-forward processes has not been made by Francis and Hermens. Modeling of AttentionModeling of the effects of attention in Di Lollo et al. 's (2000) study was based on the large literature on set-size effects in visual perception (Duncan & Humphreys, 1989; Eriksen,1995;Sperling, 1960;Treisman & Gelade, 1980). Accordingly, set size was modeled as though it influenced the time required for attention to be deployed to the location of the target. The larger the set size, the longer it takes to find the target.Current models of masking do not encompass attentional effects. This is one reason why they cannot account for Di Lollo et al. 's (2000) data. Francis and Hermens (2002) modeling attention as affecting the intensity of the mask. As set size is increased, the mask representation is assumed to become stronger whereas the target representation remains the same. We believe this modeling of attention to be inappropriate.It has long been known that the strength of metacontrast masking is directly related to mask intensity (Alpern, 1953). It is, therefore, unsurprising that weakening the mask reduces the metacontrast effect in all extant models. There is no need to expand current models along these lines because they already include the effect of mask intensity. The question that Francis and Hermens (2002) did not address is why anyone should model attention in terms of mask intensity unless they were aware of Di Lollo et al. 's (2000) results and did not have any other convenient mechanism for reducing the magnitude of the metacontrast effect. In more general terms, there is a substantial difference between claiming that current models can a...

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“…This procedure assured that, except for onset and offset, the mask as well as the target were activating only sustained channels. However, under these conditions, neither of the observers reported any disappearance or decrease in the visi- (Alpern, 1953;Kolers & Rosner, 1960;Weisstein & Growney, 1969). The interaction between target-mask spatial separation and viewing eccentricity was also statistically significant for both observers' results [B.B., F(6,84)=6.5; M.K., F(6,84)=7.8; ps < .005].…”

Section: Resultsmentioning

confidence: 83%

A single-transient masking paradigm

Breitmeyer

Rudd

1981

Perception & Psychophysics

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Visual masking, as typically studied in the twotransient paradigm (Matin, 1975), involves suppression of the visibility of one brief stimulus, the target, by another (spatio-jtemporally contiguous brief stimulus, the mask. Recent neurophysiologically based theories of visual masking rely on the existence, in the higher mammalian visual system, of short-latency, fast transient channels which inhibit longer latency, slower sustained channels (for review, see Breitmeyer & Ganz, 1976). In particular, recent theoretical approachesto visual masking, namely, thoseof Breitmeyer & Ganz (1976) and Weisstein, Ozog, and Szoc (1975), make use of this two-channel, transient-sustained distinction. Both approaches share the assumption that the typical Ll-shaped or type B metacontrast function (Kolers, 1962) is a consequence of the inhibition of the slow, target-activated sustained channels by the faster mask-activated transient channels in the target-mask sequence. The two models are similar in the specification of conditions required to activate the transient channels. For Breitmeyer and Ganz's (1976) and Weisstein et aI.'s (1975) model, it is sufficient that the mask activate fast transient channels, although both models acknowledge that either target or mask can and does activate both transient and sustained channels. The activation of transient channels by the target is not regarded as a necessary condition for obtaining metacontrast masking.However, Matin (1975)proposed a model in which activationof spatiotemporalsequence detectors, termed target-mask, or T-M, neurons, are required to produce type B metacontrast functions. In other words, Matin suggests that transient neurons may be a substrate for the T-M sequence detectors and that, in addition to the activation of mask transient neurons (Breitmeyer & Ganz, 1976;Weisstein et al., 1975), activation of target transient neurons is also necessary for producing metacontrast. The present experiment demonstrates that Matin (1975) may have been misled in her theorizing by the prevailing methodological rather than physiological facts.M. E, Rudd's present address:

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Metacontrast

Cited by 337 publications

References 16 publications

Lateral masking in visual information processing

Lateral masking in visual information processing

Object substitution without reentry?

A single-transient masking paradigm

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