Strength of visual interpolation depends on the ratio of physically specified to total edge length

Abstract

We report four experiments in which the strength of edge interpolation in illusory figure displays was tested. In Experiment 1, we investigated the relative contributions of the lengths of luminance-specified edges and the gaps between them to perceived boundary clarity as measured by using a magnitude estimation procedure. The contributions of these variables were found to be best characterized by a ratio of the length of luminance-specified contour to the length of the entire edge (specified plus interpolated edge). Experiment 2 showed that this ratio predicts boundary clarity for a wide range of ratio values and display sizes. There was no evidence that illusory figure boundaries are clearer in displays with small gaps than they are in displays with larger gaps and equivalent ratios. In Experiment 3, using a more sensitive pairwise comparison paradigm, we again found no such effect. Implications for boundary interpolation in general, including perception of partially occluded objects, are discussed. The dependence of interpolation on the ratio of physically specified edges to total edge length has the desirable ecological consequence that unit formation will not change with variations in viewing distance.In a world of discrete surfaces and objects, the distance between points will necessarily be related to the likelihood that those points are part of the same surface or object. Such a relationship would also hold for points in the projections of surfaces and objects. However, when spatial gaps are projected to observers, the projected distance between two points depends on viewing distance.

Effects of stimulus synchrony on mechanisms of perceptual organization

“…Interestingly, one additional implication of these findings is that manipulation of the size of the premask-display crosses does not influence figure-ground segmentation and/or Gestalt coding. This seems somewhat counterintuitive considering other findings (i.e, Shipley & Kelman, 1992) that show the "goodness" of Kanizsa-types figures is largely due to the separation between inducer elements. It may be that, in this instance the collinear line segments do not encourage illusory contour formation (see, e.g., Gurnsey, Poirier, & Gascon, 1996) with the result that activity across the prime, although representing the square-arrangement of the synchronous premask elements, may not be considered in the same terms as the "subjective experience" of an illusory Kanizsa square (which is directly supported by perception of the illusory contours).…”

“…Junction elements in the target display (Figure 1a) subtended 26', 51', and 1°17' of visual angle and were separated horizontally and vertically by between 2°39'-3°30', 1°48'-3°30', or 57'-3°30', for 20%, 40%, and 60% target-inducer specification conditions. These variations produced Kanizsa-type figures representing "square" figures with probabilities of .1, .45, and .71, respectively (see Shipley & Kelman, 1992). The target displays subtended between 6°59'-7°51' × 6°59'-7°51', 6°59'-8°42' × 6°59'-8°42', or 6°59'-9°33' × 6°59'-9°33', respectively.…”

“…In the present experiment, the specification of the premask and target display stimuli was systematically varied by independently and factorially varying the length of the line segments making up the crosses (premask display) and corner junctions (target display). With regard to the target display, this effectively produced a variation of the "goodness" of the Kanizsa-type square target, which, according to Shipley and Kelman (1992), is a function of the ratio of the physically specified length of the collinear inducer (junction) segments to the total edge length of the Kanizsa-type square. The ratios introduced in the experiment were 20% ("poor" square), 40%, or 60% ("good" square) (with 20% being the ratio used in previous studies).…”

Illusory contours: a window onto the neurophysiology of constructing perception

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 [95]. Shipley and Kellmann [96] independently varied inducer size, inducer spacing, and overall stimulus size of Kanizsa figures.…”

Spectral completion of partially masked sounds

“…3b, comparing conditions iii, iv, and v]. This manipulation increases the relative extent over which completion must occur and is reminiscent of the effect of the ''support ratio'' of illusory contours in the visual domain (15). Lower support ratios result in weaker illusory contours, and a similar effect may be at work in the auditory domain.…”