Degree of Handedness, but not Direction, is a Systematic Predictor of Cognitive Performance

Abstract

A growing body of evidence is reviewed showing that degree of handedness (consistent versus inconsistent) is a more powerful and appropriate way to classify handedness than the traditional one based on direction (right versus left). Experimental studies from the domains of episodic memory retrieval, belief updating/cognitive flexibility, risk perception, and more are described. These results suggest that inconsistent handedness is associated with increased interhemispheric interaction and increased access to processes localized to the right cerebral hemisphere.

Handedness and behavioural inhibition system/behavioural activation system (BIS/BAS) scores: A replication and extension of Wright, Hardie, and Wilson (2009)

“…Our findings, therefore, do not support the arguments put forward by Prichard et al (2013) that handedness effects are related more to consistency or degree than to direction of hand preference. In their view (p.1), "a major reason why previous research has failed to clearly determine individual differences in handedness effects on behavior is because the measure used to define handedness has heretofore been incorrect.…”

“…First, it suggests that the relationship is artefactual, arising from a tendency of some respondents to endorse extreme scores on both the handedness and the anxiety questionnaires. Second, Christman and his colleagues have argued that it is not so much direction, but rather degree, of handedness that is the important variable in assessing the relationship between laterality and cognitive and personality dimensions of behaviour (see Prichard, Propper & Christman, 2013).…”

“…Certainly we found no effect of strength of handedness when considered without regard to direction. Hardie and Wright (2014), using the type of classification scheme advocated by Prichard et al (2013) and a number of different cut-off values to define consistent versus inconsistent handedness, found small but statistically significant effects of consistency or strength of handedness for their sample (N=689) as a whole (consistently handed individuals had higher BIS scores than those of inconsistent handedness). However, when they looked separately at right-handers and lefthanders an effect was apparent among the 202 left-handers but not among 481 right-handers.…”

The contributions of handedness and working memory to episodic memory

“…Christman and colleagues (Christman & Propper, 2010;Prichard, Propper, & Christman, 2013) theorize that inconsistent-handers are at an advantage during episodic memory retrieval because, compared to consistent-handers, inconsistent-handers have relatively greater access to the right hemisphere and possess greater interhemispheric communication. The theory is supported by neurological findings, such as the involvement of the left prefrontal areas during encoding of verbal information and right prefrontal areas during retrieval of the same information (Tulving, Kapur, Craik, Moscovitch, & Houle, 1994), and studies showing a negative correlation between degree of handedness and volume of the corpus callosum, indicating significantly larger callosal volumes with increasing inconsistent-handedness (Habib et al, 1991;Luders et al, 2010;Witelson, 1985;Witelson & Goldsmith, 1991).…”

Lateralization and cognitive systems

“…In addition to animal research, several studies examined how lateralization impacts the functioning of different cognitive systems in the human brain. For example, it was investigated how handedness is related to other brain functions such as language lateralization (Carey and Johnstone, 2014), approach/avoidance motivation (Hardie and Wright, 2014), perceptual asymmetries (Marzoli et al, 2014), semantic priming (Fagard et al, 2014), response speed in the orthogonal Simon task (Iani et al, 2014) and cognitive performance in general (Prichard et al, 2013;Scharoun and Bryden, 2014). These studies are complemented by a review article investigating how twin studies could be useful in the quest to understand the complex interrelations of lateralization and cognitive systems (Ooki, 2014) as well as by a large-scale anatomical work investigating the effect of handedness on the structure of the cerebral cortex (Guadalupe et al, 2014).…”