Rotation of mental images and asymmetries in word recognition in disabled readers.

Abstract

Two experiments revealed marked dissimilarities in perceptual coding between impaired and fluent readers. In the first investigation, twenty-six right-handed boys with reading disability (CA = 9 to 11 years) and of average intelligence were compared to twenty-six good readers on a test of visual-spatial, short-term memory. The task required that relative spatial relations between target items be held invariant across 180 degree and 90 degree rotations of the visual field. Both groups performed equally well in their spatial recall on transformed visual fields. However, poor readers coded the test stimuli differently, in a non-analytic and synchronous fashion. In a follow-up experiment, a small group of disabled readers compared with good readers (CA = 10 years) showed a lower right-over left-field advantage when reporting single words presented tachistoscopically. Taken together, the results disconfirm the widely held ideas that poor readers are suffering from spatial disorientation, left-right confusion, mirror-image equivalence or lack of cerebral dominance. Rather, these findings suggest that the perceptual 'anomalies' often linked with reading disability may result from non-pathological variations in the structural operations used to encode visual information. Furthermore, the results suggest tentatively that this difference in the organization of encodings in visual memory may be related to asymmetries in brain functioning.

Does Dyslexia Develop from Learning the Alphabet in the Wrong Hemisphere? A Cognitive Neuroscience Analysis

“…Concordantly, dyslexic children not uncommonly produce semantic substitutions during single word reading (e.g., chicken for duck) (Siegel, 1985;Temple, 1988)-another indicator of RH processing (Coltheart, 1983). They also tend to code holistically even when an analytical approach would be more efficient (Kershner, 1979;Williams & Bologna, 1985) in a manner suggestive of RH rather than LH specialization (Atchley & Atchley, 1998;Doyon & Milner, 1991;Fink et al, 1996) and not dissimilar to a recent finding of gestalt dependence in pure alexia (Sekuler & Behrmann, 1996). Gordon (1980Gordon ( , 1988Gordon ( , 1989 has argued that a majority of those who develop dyslexia-regardless of subtype-have a genetically mediated predisposition for RH processing (see also Symmes & Rapoport, 1972).…”

The Incidence and Nature of Letter Orientation Errors in Reading Disability

“…Early accounts of these errors focused on hemispheric lateralization (e.g., Orton, 1937) and spatial and directional confusion in general as the causes of reading disability (Bender, 1957;Birch, 1962;Frostig & Maslow, 1973). However, claims challenging this spatialdirectional explanation have emerged, suggesting that orientation errors may result from the use of holistic, nonanalytic strategies to encode visual information rather than from spatial confusion (Kershner, 1979). Reversal errors do not appear to constitute an unusual proportion of the errors that children in general make in their reading (Holmes & Peper, 1977;Shake, 1982) and appear to be linguistically rather than perceptually based (Liberman, Shankweiler, Orlando, Harris, & Bell Berti, 1971;Stanovich, 1985;Vellutino, 1979Vellutino, ,1987.…”

Symmetry in Vision

“…Mirror-reversal errors may arise due to different encoding strategies, in particular, a greater reliance on holistic visual coding of the letters or words than on analytic coding of individual features to allow for greater letter discriminability. For example, poor readers also make more errors in memory for relative spatial positions and orientations of objects [89,110]. Learning to read may therefore engage a more analytic form of processing by which individual letters are identified and special attention is paid to the distinguishing features of, for example, mirror-reversible letters [104,111].…”