Analysis of distributions reveals real differences on dichotic listening scores between left- and right-handers

Abstract

About 95% of right-handers and 70% of left-handers have a left-hemispheric specialization for language. Dichotic listening is often used as an indirect measure of this language asymmetry. However, while it reliably produces a right-ear advantage (REA), corresponding to the left-hemispheric specialization of language, it paradoxically often fails to obtain statistical evidence of mean differences between left- and right-handers. We hypothesized that non-normality of the underlying distributions might be in part responsible for the similarities in means. Here, we compare the mean ear advantage scores, and also contrast the distributions at multiple quantiles, in two large independent samples (Ns = 1358 and 1042) of right-handers and left-handers. Right-handers had an increased mean REA, and a larger proportion had a REA than in the left-handers. We also found that more left-handers are represented in the left-eared end of the distribution. These data suggest that subtle shifts in the distributions of DL scores for right- and left-handers may be at least partially responsible for the unreliability of significantly reduced mean REA in left-handers.

Handedness in schizophrenia and affective disorders: a large-scale cross-disorder study

“…In our study, negative effect sizes were found for the scales "Hallucination" and for "Positive formal thought disorder", indicating higher symptom severity in schizophrenia patients with an increased tendency towards left-handedness. Since left-handed individuals are more likely to show atypical right-sided language lateralization [69], this finding suggests that handedness may be a relevant factor for the relation of schizophrenia and language lateralization that should be considered in future studies.…”

Dichotic listening and interhemispheric integration after callosotomy: a systematic review

“…1). Instructed to report the stimulus heard best, participants typically report the right-ear stimulus more frequently than the leftear stimulus when a verbal stimulus material like words or syllables is used (e.g., Bless et al, 2015;Karlsson, Hugdahl, Hirnstein, & Carey, 2023;Parker, Woodhead, Thompson, & Bishop, 2021). This right-ear advantage (REA) is traditionally interpreted to reflect the dominance of the left cerebral hemispheres for speech and language processing (e.g., Bryden, 1988;Carey & Johnstone, 2014;Hugdahl & Westerhausen, 2016;Kimura, 1967;Westerhausen & Kompus, 2018;Wexler, 1988).…”