Quantitative Assessment of Five Behavioural Laterality Measures: Distributions of Scores and Intercorrelations Among Right-handers

Abstract

Five behavioural laterality measures (degree of right-handedness, ear dominance, ocular dominance, line bisection performance, and lateral preference as assessed by preferred direction of conjugate lateral eye movem ents) were analysed in 1171 right-handers by merging data from 15 different samples. All laterality aspects were assessed quantitatively by using well controlled performance measures instead of questionnaires. The distributions and intercorrelations of the measures as well as their test±retest reliabilities were examined. Results show moderately high reliabilities for all m easures, and clearly demonstrate considerable variability am ong dextrals in the direction and m agnitude of the obtained behavioural laterality m easures. Most importantly, independence of the different measures questions some common assumptions in laterality research. It seems unlikely, for instance, that handedness and other aspects of laterality may be a product of one single underlying m echanism of brain lateralisation. INTRODUCTIONIn laterality research, various behavioural assessment methods have been applied in order to measure asym m etries in hemisphere functions. The most frequently investigated aspect of behavioural laterality is handedness. In agreem ent with a tradition in early laterality research, many authors implicitly or explicitly proceeded on the assumption that handedn ess (or other asymm etry measures) m ay be an indicator of a single fundam ental left±right dimension that unde rlies all hem isphere asym metries. This supposition is manifest in the LAT ERALITY, 1999, 4 (4), 345±362Requests for reprints should be sent to Dr.

What does the dominant eye dominate? A brief and somewhat contentious review

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