Cognitive and psychophysiological correlates of handedness and reading ability

Data on handedness and cognitive skills are available from six separate studies of reading development and of developmental dyslexia, compromising a data base on 410 children aged between 7 and 12 years. One hundred and thirty eight of these children have been identified as suffering from dyslexia; the remaining 272 are chronological- or reading age-matched controls. Additional information on cortical lateralisation is available for 186 of these children, via EEG or ERP data. In all cases, handedness has been assessed by use of the Annett pegboard giving a measure of relative left-right hand skill. Phonological processing skills were measured using the simple rhyme awareness task developed by Bryant and Bradley; visuospatial skills were assessed via the WISC Picture completion test, or the Block design and matching of Letter-like forms task from the British Ability scales. EEG measures and ERP measures were obtained with a 28 channel Brain Electrical Activity Mapping system. These data are examined to explore specific hypothesis generated by Annett’s right shift theory:
Do putatively RS-participants show evidence of reduced left hemisphere dominance in language tasks
Do putatively RS-participants show evidence of reduced left hemisphere function?
Do putatively RS + + participants show evidence of strong left hemisphere dominance in language tasks.
Do putatively RS + + participants show evidence of impaired right hemisphere function?
Results indicate strong support for the first two questions. There is some support for the last two, but it is more indirect. These findings are discussed in the context of Annett’s Right Shift Theory.

Abstract from the 8th World Congress of Psychophysiology, Tampere, Finland, 25–29 June, 1996