Developmental instability and right shift theory hypotheses concerning correlates of familial sinistrality: negative...

Both the right shift (Annett, 1985) and developmental instability (Yeo & Gangestad, 1993) theories of handedness predict that familial sinistrality (FS) should relate to hand skill asymmetries (HSA) on peg-moving tasks. Annett also hypothesises that both HSA and a procedure she derived for classifying individuals according to the pattern of their hand preferences for different manual activities can index the genotypes posited in her theory, i.e. she believes these variables are highly correlated. These hypotheses were tested in a sample of 280 dextral college students. Results failed to support the finding of Gangestad and Yeo (1994) that subjects showing greater hand skill asymmetry deviations from typical asymmetry had a greater probability of having a left-handed parent. There was also no support for Annett's finding that greater dextrality, as defined by her hand preference classification system, was negatively associated with familial sinistrality. Additionally, the relationship between HSA and Annett's hand preference classes was found to be exceedingly weak, contrary to Annett's theorising. These and other failures to find highly replicable differences between FS- and FS+ dextrals cast doubt on the validity of genetic or partial-genetic theories of handedness that posit a ''penetrance'' of a recessive non-dextrality-favouring gene that causes presumed dextral heterozygotic persons to differ from presumed homozygotic dominant persons in cognitive or manual skills.