Holistic processing of Chinese characters in college students with dyslexia

Abstract

Expert face recognition has long been marked by holistic processing. Hence, due to the many visual properties shared between face perception and Chinese characters, it has been suggested that Chinese character recognition may induce stronger holistic processing in expert readers than in novices. However, there have been different viewpoints presented about Chinese character recognition, one of which suggests that expertise in this skill involved reduced holistic processing which may be modulated by writing experiences/performances. In this study we examined holistic processing in Chinese character recognition in adults with and without dyslexia, using the complete composite paradigm. Our results showed that the adults with dyslexia recognized Chinese characters with a stronger holistic processing effect than the typical controls. It seems that those with dyslexia relied overly on the visual spatial information of characters and showed deficits in attending selectively to their components when processing Chinese characters, which hindered the development of expert reading and writing skills. This effect was in contrast to previous perceptual expertise studies in which reduced holistic processing marked deficits in face/visual object recognition. This study is also the first to show that Chinese adults with dyslexia had persistent below average performances in Chinese literacy.

Figure 1

Complete composite paradigm to measure holistic processing. In each trial, participants were cued to attend to the top or bottom half of each stimulus pair and judged whether the attended halves were the same or different (attended halves shaded in grey in the figure). Holistic processing was demonstrated by a lower performance level in the incongruent condition than in the congruent condition, induced by the interference of the irrelevant halves. This paradigm has been widely adopted to measure for holistic processing in face recognition.

Figure 2

A′ and Response Time (shown in congruent and incongruent trials in both aligned and misaligned conditions) in dyslexics (top) and typically developing readers (bottom).

Figure 3

Centralized Residuals of A′ (left) and response time (right) as computed with regression method.

Figure 4

(a) Regression between residuals of A′ and centralized literacy scores; (b,c) regression between residuals of response time and centralized literacy and dictation scores.

Figure 5

Illustration of stimulus pairs in the complete composite paradigm (a) and trial sequences (b). In (a), the four conditions used in the paradigm are shown; the attended components are shaded in grey. In (b), a 1000 ms central fixation cross precedes each trial, followed by a cue either below or above the cross, or to the left or right of it, to indicate which halves (top or bottom/left or right) of the characters the participant should attend to in the subsequent display.

Figure 6

Example of the stimulus pairs in aligned and misaligned conditions.