The same binding in contour integration and crowding

Abstract

Binding of features helps object recognition in contour integration, but hinders it in crowding. In contour integration, aligned adjacent objects group together to form a path. In crowding, flanking objects make the target unidentifiable. But, to date, the two tasks have only been studied separately. May and Hess (2007) suggested that the same binding mediates both tasks. To test this idea, we ask observers to perform two different tasks with the same stimulus. We present oriented grating patches that form a “snake letter” in the periphery. Observers report either the identity of the whole letter (contour integration task) or the phase of one of the grating patches (crowding task). We manipulate the strength of binding between gratings by varying the alignment between them, i.e. the Gestalt goodness of continuation, measured as “wiggle”. We find that better alignment strengthens binding, which improves contour integration and worsens crowding. Observers show equal sensitivity to alignment in these two very different tasks, suggesting that the same binding mechanism underlies both phenomena. It has been claimed that grouping among flankers reduces their crowding of the target. Instead, we find that these published cases of weak crowding are due to weak binding resulting from target-flanker misalignment. We conclude that crowding is mediated solely by the grouping of flankers with the target and is independent of grouping among flankers.

Grouping, pooling, and when bigger is better in visual crowding

“…Livne and Sagi (2007) proposed that flanker-flanker grouping determines crowding (see also Livne & Sagi, 2010). With the same set of stimuli, but in different configurations, Chakravarthi and Pelli (2011) showed evidence that only local target-flanker binding matters, i.e., the global flanker-flanker configuration does not matter-an interpretation countered by Livne and Sagi (2011). Our results with vernier stimuli favor an explanation in terms of global target-flanker grouping because adding flankers can weaken crowding, and good Gestalt and regularity matter (Figures 1, 3, and 4; Malania et al, 2007;Saarela et al, 2009;Sayim et al, 2010; but see Felisberti et al, 2005).…”

Detecting distortions of peripherally presented letter stimuli under crowded conditions

“…The results from our second experiment show that distorted targets do not pop out from undistorted flankers (and vice versa). This is interesting in light of the extensively documented effects of target-flanker similarity in crowding (Estes, 1982;Wilkinson et al, 1997;Kooi et al, 1994;Bernard & Chung, 2011;Chung et al, 2001;Chakravarthi & Pelli, 2011;Glen & Dakin, 2013;Livne & Sagi, 2007;2010;Herzog et al, 2015;Manassi et al, 2013;Saarela et al, 2009;Sayim & Cavanagh, 2013). If we define "similarity" at the level of "distortedness", then in Experiment 1 the distorted target becomes less similar to the undistorted flankers as distortion amplitude increases.…”

“…As mentioned above, there is strong evidence from a number of studies that local orientation processing is impaired by crowding. Sensitivity to local position (Dakin et al, 2010;Greenwood et al, 2009;, spatial frequency (Wilkinson et al, 1997), curvature (Kramer & Fahle, 1996), and contour alignment (Robol et al, 2012;Dakin & Baruch, 2009;May & Hess, 2007;Chakravarthi & Pelli, 2011) is also impaired by flanking elements. Some or all of these potential cues could therefore be related to the effects we observe.…”

Chinese-character crowding—I. Effects of structural similarity

“…Contour alignment was found to modulate crowding strength (Chakravarthi & Pelli, 2011;Glen & Dakin, 2013) and might contribute to the weakened crowding in the scrambled-character crowded condition. Rotation was involved when we scrambled the characters and could have made alignment of strokes from target and from flankers less likely.…”