E-Readers Are More Effective than Paper for Some with Dyslexia
Figure 5
A proposed explanation: Short lines guide attention to the uncrowded span.
(A) Crowding is easily demonstrated. Fixating on the red line, most of the characters in the word “visual” can be identified, while those in the adjacent word “covert” (say, the letter “r”), viewed peripherally, are difficult to discern. However, when peripheral letters are viewed in isolation (the “r” to the right), the uncluttered text is more readily identified. This peripheral interaction phenomenon is referred to as crowding [67]. (B) Crowding increases with angle from fixation, as suggested schematically by the stippling. Given this, only the word closest to fixation (“visual”) falls within the “uncrowded span” [10] that is easily read. (C) Therefore, as the gaze shifts during reading, attention (here suggested using a radial blur) must track the uncrowded span as fixations advance. (D) However, for those with attention deficits, attention shifting is sluggish [53], and we suggest that this causes attention to be slow to disengage from the previously fixated word (“covert”) as the gaze advances. Attention is therefore over-emphasized in the periphery (left of fixation), where words are subject to crowding and difficult to discern. We propose that these factors conspire to make reading difficult in some people with attentional forms of dyslexia. (E) Short lines ameliorate such deficits by guiding attention to the uncrowded span, while minimizing confusion caused by the presence of crowded text to the left of fixation.