Lateral masking: Limitations of the feature interaction account

Abstract

Recognition performance for a target letter embedded in a string of characters is worse than that for targets presented in isolation. This lateral masking (LM) effect is known to depend on target eccentricity and spacing between target and flankers (Bouma, 1970),indicating that LM arises in early visual processing due to interactions among visual features. The feature interaction account would predict that flankers consisting of similar features produce similar LM effects and that differences in LM produced by different types of flanker diminish with increasing target eccentricity and decreasing spacing. However, in a series of six experiments, this prediction was shown not to be true. Flankers that did not access a higher level code (e.g., pseudoletters or rotated letters) produced more LM than standard letter flankers. Moreover,effects of different flanker types were most pronounced for medium target eccentricities and medium spacings for which recognition performance scores ranged between 400A> and 600A>.

On the relations between crowding and visual masking

“…Also, crowding effects depend on the kinds of flankers/masks (Bouma, 1970;Huckauf, Heller, & Nazir, 1999;Styles & Allport, 1986). One example is that letter-like nonletter flankers produce more crowding than letter flankers do (Huckauf et al, 1999). This so-called letter superiority effect seems paradoxical, since one would expect a facilitation when presenting flanking characters of a set different from the target.…”

“…For example, masks consisting of letter segments, letters, or words produce different recognition performances for the same target letters (e.g., Massaro & Cohen, 1994;Taylor & Chabot, 1978;Turvey, 1973). Also, crowding effects depend on the kinds of flankers/masks (Bouma, 1970;Huckauf, Heller, & Nazir, 1999;Styles & Allport, 1986). One example is that letter-like nonletter flankers produce more crowding than letter flankers do (Huckauf et al, 1999).…”

Contrasting effects of sensory limits and capacity limits in visual selective attention

“…These nontarget letters were response neutral, so that the manipulation of set size did not vary the number of response alternatives. Moreover, we ensured that the spacing between individual letters in the circle was sufficient to preclude effects of lateral masking or crowding (Huckauf, Heller, & Nazir, 1999;Strasburger, Harvey, & Rentschler, 1991; see also Wolford & Chambers, 1983). In the condition of low perceptual load with degraded targets, the target letter was approximately half the size that it was in the other conditions, and the contrast intensity of the target stimulus was substantially reduced.…”

The relative benefit of word context is a constant proportion of letter identification time

“…The impact of lateral masking and visual crowding are reduced when the flanking stimuli are moved farther from the target stimulus (Flom, 1991;Flom et al, 1963;Huckauf et al, 1999;Kooi, Toet, Tripathy, & Levi, 1994;Loomis, 1978;Toet & Levi, 1992;Wolford & Chambers, 1983). In addition, as spacing increases, positional uncertainty should decrease.…”

“…Specifically, do manipulations that are known to change the degree of visual crowding similarly change the benefit of word context. Although visual crowding can occur at the fovea (see Flom, Weymouth, &Kahneman, 1963, andJacobs, 1979, among others), it has a far greater impact at the retinal periphery (Flom, 1991;Flom et al, 1963;Huckauf, Heller, & Nazir, 1999;Jacobs, 1979;Latham & Whitaker, 1996;Nazir, 1992;Strasburger, Harvey, & Rentschler, 1991). In the study mentioned above (Fine, 2001), changes in letter identification accuracy were looked at only at the periphery, where visual crowding is more pronounced.…”