No association between adult sex steroids and hand preference in humans

Abstract

Background: There is ongoing debate about the effects of hormones on the lateralization of the developing brain. In humans, there are conflicting theories of how testosterone during development should affect lateralization. Empirical studies linking prenatal and postnatal testosterone levels to hand preference (a proxy for lateralization) are similarly mixed. Links between hand preference and health may also suggest a mediating role of steroid hormones such as testosterone and estradiol. Studies to date of adult steroid hormones and handedness have been hindered by samples that contain small numbers of non-righthanders.Results: In the largest study of the phenomenon to date, I find that the testosterone (n = 7290) and estradiol (n = 3700) levels of left-and mixed-handed adults are no different to those of right-handers. All Bayesian 95% highest density intervals contained 0.Discussion and conclusions: The results have implications for studies that show elevated risk of hormonal-related mental and physical disorders in lefthanded individuals.

Development of laterality: Asymmetrical human behaviors and perceptual biases

“…The delay in the development of the left hemisphere will result in a compensatory growth of the right hemisphere's homolog regions, increasing the incidence of left-handedness (Beking et al, 2018;Geschwind & Galaburda, 1985). Although this theory has been challenged (e.g., Bryden et al, 1994;Richards, Medland et al, 2021;Richardson, 2022), there is some evidence supporting testosterone's influence on lateralization. For example, Lust et al (2011) found that a high level of prenatal testosterone is related to a weaker handedness and stronger cerebral dominance for language among 6-year-old children.…”

“…Although it remains unclear how sex hormones can be involved in functional lateralization, it is hypothesized that they may influence interhemispheric connection affecting the interaction/inhibition between the two hemispheres (for review see Hausmann, 2017). It is noteworthy that recent evidence showed an absence of an association between female sex hormones and hand preference (Richardson, 2022).…”