"But Masaki has shown the snake might actually speed up the fixation of sinistrality
, suggesting this is a very plausible speciation mechanism," he added.
Some effect of Rh-incompatibility was suggested as a possible cause of sinistrality in a few males.
Corballis (1997) suggests that an infrequent gene with a capacity to increase the rate of sinistrality slightly in sons above that of daughters could be located on the X chromosome and modify the effects of an autosomal handedness gene, as theorized by McManus and Bryden (1992).
122-123) feel that any contribution of pregnancy/birth risk factor influences on handedness would be of very small magnitude, Ashton (1982) concluded that 28 % of left-handed females might owe their sinistrality to such factors, and McKeever, Suter, and Rich (1995), quite independently of Ashton's estimate, suggested that as many as 29 % of sinistral females might owe their sinistrality to maternal age and birth order factors.
In Annett's hand preference classification procedure, the basic decision as to the sinistrality or dextrality of the individual is made on the basis of the hand preferred for writing.
The influence of handedness, sex, familial sinistrality, and androgyny on language laterality, verbal ability, and spatial ability.
The influences of handedness, sex, familial sinistrality
, and androgyny on language laterality, verbal ability and spatial ability.
Many small-scale studies have investigated the relationship between handedness and intelligence (and/or talent), along with sex and familial sinistrality
as moderating variables; in reviewing the topic O'Boyle & Benbow (1990) concluded that 'the variability of |the~ findings speaks to the likelihood of a Type 1 error'.
Within the Kerr/Carr families there should also have been a very specific pattern of increased sinistrality, in which the raised sinistrality would have been present only in male family members who were ancestors or descendants of male Kerrs or Carrs.
However this need not indicate that there is generally a raised incidence of sinistrality in family members.