Perceptual learning eases crowding by reducing recognition errors but not position errors

Abstract

When an observer reports a letter flanked by additional letters in the visual periphery, the response errors (the crowding effect) may result from failure to recognize the target letter (recognition errors), from mislocating a correctly recognized target letter at a flanker location (target misplacement errors), or from reporting a flanker as the target letter (flanker substitution errors). Crowding can be reduced through perceptual learning. However, it is not known how perceptual learning operates to reduce crowding. In this study we trained observers with a partial-report task (Experiment 1), in which they reported the central target letter of a three-letter string presented in the visual periphery, or a whole-report task (Experiment 2), in which they reported all three letters in order. We then assessed the impact of training on recognition of both unflanked and flanked targets, with particular attention to how perceptual learning affected the types of errors. Our results show that training improved target recognition but not single-letter recognition, indicating that training indeed affected crowding. However, training did not reduce target misplacement errors or flanker substitution errors. This dissociation between target recognition and flanker substitution errors supports the view that flanker substitution may be more likely a by-product (due to response bias), rather than a cause, of crowding. Moreover, the dissociation is not consistent with hypothesized mechanisms of crowding that would predict reduced positional errors.

Two-stage perceptual learning to break visual crowding

“…It is well known that training can improve performance for many visual tasks (Sagi, 2011;Watanabe & Sasaki, 2015). Consistent with this, several previous studies (Chung, 2007;Huckauf & Nazir, 2007;Hussain et al, 2012;Sun et al, 2010;Xiong et al, 2015) trained human subjects on a crowded letter identification task and found that crowding could be ameliorated by training. Performance improvements ranged from 30% to 88%, depending on the amount of training.…”

“…One might ask whether training could reduce crowding and improve peripheral vision. Recent studies (Chung, 2007;Huckauf & Nazir, 2007;Hussain, Webb, Astle, & McGraw, 2012;Sun, Chung, & Tjan, 2010;Xiong, Yu, & Zhang, 2015) have demonstrated that, following training, the accuracy of crowded letter identification and the spatial extent of crowding could be significantly reduced. This finding not only is theoretically interesting because it opens a new window to understand the mechanisms of visual crowding from a perspective of perceptual learning but also provides a new noninvasive treatment for children and adults with amblyopia.…”

Perceptual Learning of Visual Span Improves Chinese Reading Speed

“…[36][37][38] However, recently, researchers have found that the effects of perceptual learning can be generalized to different stimulus locations and orientations. [39][40][41][42] Importantly, some studies have documented that low-level training paradigms can improve high-level cognitive processes such as attention, reading fluency, and working memory recall ability. 8,9,11,14,15,43 These results imply that high-level cognitive functions, such as reading, can be improved by basic perceptual learning.…”

Visual crowding involves delayed frontoparietal response and enhanced top‐down modulation

“…When a peripherally presented target, which is easily recognized on its own, is surrounded by nearby flankers, its recognition performance is often largely disrupted (Levi, ; Whitney & Levi, ). This phenomenon, referred to as crowding, is not only a well‐established effect in spatial vision which occurs under a wide range of conditions and tasks but also a basic property of peripheral vision that sets the limit for peripheral perception (Anderson, Dakin, Schwarzkopf, Rees, & Greenwood, ; Chen et al., ; Chicherov & Herzog, ; Chicherov, Plomp, & Herzog, ; Greenwood, Sayim, & Cavanagh, ; Herzog, Sayim, Chicherov, & Manassi, ; Levi, ; Manassi, Sayim, & Herzog, ; Ronconi, Bertoni, & Marotti, ; Shin, Chung, & Tjan, ; Whitney & Levi, ; Xiong, Yu, & Zhang, ; Zhang, Zhang, Liu, & Yu, ). It is of vital importance to study crowding and its underlying neural mechanism, as it would advance our understandings of conscious vision and object recognition.…”

“…2015; Levi, 2008;Manassi, Sayim, & Herzog, 2012;Ronconi, Bertoni, & Marotti, 2016;Shin, Chung, & Tjan, 2017;Whitney & Levi, 2011;Xiong, Yu, & Zhang, 2015;Zhang, Zhang, Liu, & Yu, 2012). It is of vital importance to study crowding and its underlying neural mechanism, as it would advance our understandings of conscious vision and object recognition.…”