Article

Difficulties in visual attention are increasingly being linked to dyslexia. To
date, the majority of studies have inferred functionality of attention from
response times to stimuli presented for an indefinite duration. However, in
paradigms that use reaction times to investigate the ability to orient attention,
a delayed reaction time could also indicate difficulties in signal enhancement or
noise exclusion once oriented. Thus, in order to investigate attention modulation
and visual crowding effects in dyslexia, this study measured stimulus
discrimination accuracy to rapidly presented displays. Adults with dyslexia (AwD)
and controls discriminated the orientation of a target in an array of different
numbers of - and differently spaced - vertically orientated distractors. Results
showed that AwD: were disproportionately impacted by (i) close spacing and (ii)
increased numbers of stimuli, (iii) did use pre-cues to modulate attention, but
(iv) used cues less successfully to counter effects of increasing numbers of
distractors. A greater dependence on pre-cues, larger effects of crowding and the
impact of increased numbers of distractors all correlated significantly with
measures of literacy. These findings extend previous studies of visual crowding
of letters in dyslexia to non-complex stimuli. Overall, AwD do not use cues less,
but they do use cues less successfully. We conclude that visual attention is an
important factor to consider in the aetiology of dyslexia. The results challenge
existing theoretical accounts of visual attention deficits, which alone are
unable to comprehensively explain the pattern of findings demonstrated here.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS