Aspects of phonological processing in sub-groups of left and right handedness
thesisposted on 15.12.2014, 10:46 by Pamela. Smythe
This thesis was begun with two intentions. The first was to test a hypothesis of the Annett Right Shift Theory (1972, 1985) that people with poor phonology are less biased to right-handedness than the general population. The second was to establish whether to reduced bias to dextrality applies to deficits in all types of phonological processing.;Evidence for an association between poor phonological processing and reduced dextrality was demonstrated in an age cohort of schoolchildren and in two large undergraduate samples. Cases of 'pathological' handedness are unlikely to have caused the association as, in children, the differences increased when those with slow hand skill and poor vocabularies were removed. Support for a genetic influence upon phonological processing was found when groups of children and undergraduates with varying phonological ability also varied for their relatives' handedness.;Although, as expected, undergraduates with problems with nonword rhyme were more often left-handed and had more left handed relatives, against predictions, those with phoneme discrimination difficulties were much more dextral in handedness and had fewer left handed relatives. These interesting results were further investigated and poor ability in either phonological production/segmentation or rhyme/awareness was found to be associated with a reduced shift to dextrality. Finally an atypical pattern in dichotic listening (equal errors at each ear) was associated with phonological awareness difficulties, as was the atypical pattern of absence of shift to dextrality in handedness.;The findings suggest that poor phonological awareness or phonological production/segmentation could be a risk in the rs - genotype and minor phoneme perception problems could be a disadvantage for the rs++ genotype. It is also suggested that the latter could be part of a multi-sensory problem (Stein and Walsh, 1997). These questions are discussed further and the contributions, limitations and implications of the work are reviewed.