The Role of Illumination Level in the Strength of Subjective Contours

Warm, Joel S.; Dember, William N.; Padich, Robert; Beckner, John; Jones, Scott B.

doi:10.1007/978-1-4612-4760-9_19

Cited by 10 publications

(9 citation statements)

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“…Dumais and Bradley (1976) initially found that contour clarity increased with decreasing ambient illumination of a Kanizsa figure, a finding supported by Brussel et al (1977). However, these results have been cast into doubt by Warm, Dember, Padich, Beckner, and Jones (1987), Spillman et al (1984), and others (Parks & Marks, 1983;Watanabe & Oyama, 1988). Warm et al found that the clarity of a Kanizsa figure decreased with decreasing illumination, while Spillman et al (1984) discovered the same relation between illusory brightness and illumination in an Ehrenstein configuration.…”

Section: Low-level Determinantsmentioning

confidence: 94%

Illusory contours: Toward a neurally based perceptual theory

Lesher

1995

Psychon Bull Rev

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Although illusory contours were first described nearly a century ago, researchers have only recently begun to approach a consensus on the processes underlying their formation. Neurophysiological and psychophysical evidence indicate that neural mechanisms of the early visual cortex subserve illusory contour generation, although cognitive factors play important roles in determining the fmal percept. I summarize experiments concerning the determinants of illusory contour strength and form, concentrating on findings particularly relevant to modeling. After establishing arguments for the early generation of illusory contours, I provide an overview of formation theories, culminating with descriptions of neural models. The constraints that experimental data place on models are outlined, and neural models are evaluated with respect to these constraints. Throughout the review,I indicate where further experimental and modeling research are critical.Schumann introduced the first illusory contour, depicted in Figure 1a, in 1900, noting that a central "white rectangle with sharply defined contours appears, which objectively are not there." Schumann had discovered and noted two salient features of illusory figures: sharp edges in regions of homogeneous luminance, and a brightening within the figure. Perhaps because this stimulus failed to yield particularly convincing illusory contours, it was not until more than 50 years later that illusory contours became a topic for activeresearch. Although Ehrenstein (1941) demonstrated stimuli with salient illusory contours, it is remarkable that he failed to note their existence in the text of his article explicitly, commenting instead only on illusory brightening effects. Kanizsa's (1955) stunning figures, examples of which are depicted in Figures Iband 1c, produced extremely sharp, salient contours along with obvious brightening, initiating a wave of research.Although there have been a number ofexcellent illusory contour review papers Meyer & Petry, 1987;Parks, 1984), research advances in the psychophysical, neurophysiological, and modeling domains have been more than sufficient to mandate a new summary ofthe literature. Inthis review, I will not only present more recent data, but also employ an approach to the summaries that is markedly different from those previously taken. At the time of the earlier reviews, determination of the locus of formation of illusory contours was the central issue in illusory contour research, a fact reflected in the structure of the review papers. Experimental results were presented primarily in the historical context of supporting or refut-I would like to thank Ennio Mmgolla of Boston University for generously providing many helpful comments and suggestions during the development ofthis review.

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Section: Low-level Determinantsmentioning

confidence: 94%

Illusory contours: Toward a neurally based perceptual theory

Lesher

1995

Psychon Bull Rev

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“…on phenomenal measures (e.g. rating the strength of the subjective ®gure, as in Warm, Dember, Padich, Beckner, & Jones, 1987; though see Dresp & Bonnet, 1995;Rubin, Nakayama, & Shapley, 1996, for more objective measures). Moreover, most studies have taken such phenomenal measures while presenting just a single subjective ®gure display to the observer, often for unspeeded visual inspection and self-rating.…”

Section: Phenomenology and Its Limits Once Againmentioning

confidence: 99%

Segmentation, attention and phenomenal visual objects

et al. 2001

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Issues concerning selective attention provoke new questions about visual segmentation, and vice-versa. We illustrate this by describing our recent work on grouping under conditions of inattention, on change blindness for background events and the residual processing of undetected background changes, on modal versus amodal completion in visual search, and the differential effects of these two forms of completion on attentional processes, and on attentional modulation of lateral interactions thought to arise in early visual cortex. Many of these results indicate that segmentation processes substantially constrain attentional processes, but the reverse in¯uence is also apparent, suggesting an interactive architecture. We discuss how the`proto-objects' revealed by studies of segmentation and attention (i.e. the segmented perceptual units which constrain selectivity) may relate to other object-based notions in cognitive science, and we wrestle with their relation to phenomenal visual awareness. q

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“…There are some exceptions, however. Inducing-area contrast and target luminance, both previously found to have a strong influence upon the salience of subjective contours (Brigner & Gallagher, 1974;Gregory, 1977;Jory & Day, 1979;Warm et al, 1987), had only minimal effects upon perceptual stability. The absence of strong luminance effects was surprising, since this factor plays a critical role in the perceived sharpness and clarity of subjective contours (Dumais & Bradley, 1976;Parks & Marks, 1983, 1985Ronchi & Mori, 1959;Warm et aI., 1987).…”

Section: Discussionmentioning

confidence: 71%

“…For example, geometric illusions and reversible figures can be perceived with subjective contours, they are subject to figural aftereffects, they can be placed in apparent motion, and they are susceptible to kinetic depth information (cf. Warm, Dember, Padich, Beckner, & Jones, 1987).…”

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confidence: 99%

“…Several studies have shown that contour clarity and depth stratification vary inversely with target luminance (Bradley & Dumais, 1984;Parks & Marks, 1983, 1985. In addition, contour clarity and apparent brightness vary directly with the contrast between inducing areas and their background (Warm et al, 1987), and the apparent brightness of subjective figures also varies directly with the size of their inducing areas (Brigner & Gallagher, 1974). Moreover, the visibility of subjective contours is enhanced when the contours lie along cardinal as opposed to oblique coordinates (Vogels & Orban, 1987), a result reminiscent of the oblique ef feet in the perception of real contours (Appelle, 1972).…”

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confidence: 99%

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Determinants of stability in the perception of subjective contour

Laurie

Warm

Dember

et al. 1994

Perception & Psychophysics

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The present study constituted an initial experimental effort to examine the fragmentation characteristics of subjective contours within the photopic and upper scotopic ranges of illumination. Four stimulus factors known to influence the visibility of subjective contours-target luminance, inducing area size and contrast, and contour orientation-were examined. Results indicated that subjective contours are indeed unstable perceptual phenomena. On the average, fragmentation or fading occurred after only 15 sec of observation, and some form of stimulus outage was present for 28 % of the viewing time of each stimulus. Fragmentation latency was significantly shorter and total time in fragmentation longer for diamond than for square contours, and total time in fragmentation varied inversely with inducing-area size. Fragmentation tended to occur in whole units rather than in isolated elements, a result reminiscent of the fading of real contours under impoverished viewing conditions.

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The Role of Illumination Level in the Strength of Subjective Contours

Cited by 10 publications

References 0 publications

Illusory contours: Toward a neurally based perceptual theory

Illusory contours: Toward a neurally based perceptual theory

Segmentation, attention and phenomenal visual objects

Determinants of stability in the perception of subjective contour

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