In terms of 'educational success', the results indicated that success was lowest in the most sinistral group and rose with increasing dextrality across the remaining three groups.
The primary purpose of the present study was to test the hypothesis that degree of dextrality, as defined by Annett's hand preference classes, would be negatively related to visuospatial ability.
This indicates that dextrality was associated with better visuospatial performance in males.
This hypothesis predicts that cognitive scores will increase as a function of decreasing dextrality when the latter is indexed by Annett's hand preference classes (Annett, 1970, 1993) or by peg moving asymmetries.
In the light of this model, relatively small differences imply very large effects for the rs + gene which is presumed to be responsible for the shift to dextrality.
Spatial ability appears to be at risk in the presence of bias to dextrality in left-handers and in right-handers (Annett, 1992b).
Predictions about which abilities should show linear trends (positive or negative) or quadratic trends with increasing bias to dextrality will become clearer as the hypothesis of a BP + HA is further developed.
Right handers with the weakest bias to dextrality (class 4, who were outstanding for spatial ability in children and students) had more left-handed children than right-handers with the strongest bias to dextrality (class 2, who had the lowest scores for spatial ability) (Annett, 1992d, in press).
A double dissociation between specific deficits for auditory versus visual memory for words and the absence of the shift to dextrality versus its strong presence.