Schizotypy is increased in mixed-handers, especially right-handed writers who use the left hand for primary actions

Abstract

Associations between schizotypy and handedness were examined in 733 undergraduates for the Sta and Unex scales of the O-Life inventory and several measures derived from the Annett hand preference questionnaire. Higher schizotypy scores were found for mixed-handers defined in various ways, including inconsistent preference for any item of the questionnaire and also the presence of either hand responses. There was a marked elevation of schizotypy scores (p < .001) for righthanded writers who prefer the left hand for other 'primary' actions (throwing, racket, match, hammer, toothbrush and scissors). This observation was replicated in 182 students assessed on the Rust Scale of Schizotypal Cognitions. Several findings agree that inconsistent hand preference is associated with a raised probability of schizotypal thinking.

Psychotic-like symptoms and positive schizotypy are associated with mixed and ambiguous handedness in an adolescent community sample

“…Annett's 7-and 3-way classifications showed that lefthanders did not differ significantly from other groups. Contrary to previous findings Moran, 2006 andShaw et al, 2001), the pure left-handed group did not differ from the mixed-or right-handed groups. In our study, Annett's 7-way right-handers with strong/moderate left tendencies (i.e., mixed handed) were more psychosis-prone than pure right-handed subjects.…”

“…Some of our findings are consistent with previously reported studies on the association of handedness with psychosis-proneness in nonclinical samples (e.g., Somers et al, 2009, Chapman et al, 2011and Hori et al, 2012. Corroborating previous findings (Shaw et al, 2001, Gregory et al, 2003and Annett and Moran, 2006, writing hand alone was not associated with psychosis-proneness. Annett's 7-and 3-way classifications showed that lefthanders did not differ significantly from other groups.…”

“…Moreover, as in the study by Shaw et al (2001), this association appeared particularly dependent on subjects who used "either" hand for less commonly ambiguous actions. Similarly, Annett and Moran (2006) found that the highest schizotypy scores corresponded to right-handed writers who perform other primary actions with the left hand. These authors suggested that discordance for primary actions is not a general risk for both right-and left-handed writers, but only for the former, suggesting that the classification of mixed-handedness should be further refined to examine the specific subgroup of right-handed writers who perform other primary actions with the left hand.…”

“…Consistent with previous research in this area (e.g. Claridge et al, 1998, Shaw et al, 2001and Annett and Moran, 2006, we follow Annett's (1985) scoring revision with the original group 5 (Right-strong Left) being re-classified into either three or four, maintaining the original numbering of the remaining groups.…”

“…Similarly, several studies in nonclinical subjects have found that psychosis-proneness is associated with mixed handedness (Chapman and Chapman, 1987, Kim et al, 1992, Poreh, 1994, Richardson, 1994, Claridge et al, 1998, Shaw et al, 2001, Gregory et al, 2003, Annett and Moran, 2006, Schürhoff et al, 2008and Chapman et al, 2011, although some studies have found associations with both left and mixed handedness (Kelley andCoursey, 1992 andPoreh et al, 1997).…”