The depth and breadth of multiple perceptual asymmetries in right handers and non-right handers

ABSTRACT

Several non-verbal perceptual and attentional processes have been linked with specialization of the right cerebral hemisphere. Given that most people have a left hemispheric specialization for language, it is tempting to assume that functions of these two classes of dominance are related. Unfortunately, such models of complementarity are notoriously hard to test. Here we suggest a method which compares frequency of a particular perceptual asymmetry with known frequencies of left hemispheric language dominance in right-handed and non-right handed groups. We illustrate this idea using the greyscales and colourscales tasks, chimeric faces, emotional dichotic listening, and a consonant–vowel dichotic listening task. Results show a substantial “breadth” of leftward bias on the right hemispheric tasks and rightward bias on verbal dichotic listening. Right handers and non-right handers did not differ in terms of proportions of people who were left biased for greyscales/colourscales. Support for reduced typical biases in non-right handers was found for chimeric faces and for CV dichotic listening. Results are discussed in terms of complementary theories of cerebral asymmetries, and how this type of method could be used to create a taxonomy of lateralized functions, each categorized as related to speech and language dominance, or not.

KEYWORDS:

• Handedness
• cerebral dominance
• dichotic listening
• chimeric faces
• greyscales

Acknowledgements

We are extremely grateful to all the authors who provided us with LIs for their individual participants: Abdul Alzahrani, David Boles, Xiaohua Cao, Rodrigo Cardenas, Jiaqing Chen, Harry Chung, Michael Corballis, Lorin Elias, Michael English, Trista Friedrich, Gina Grimshaw, Melita Giummarra, Lauren Harris, Markus Hausmann, Bobby Innes, Michal Lavidor, Gemma Learmonth, Chenglin Li, Jason Mattingley, Mike Nicholls, Matthias Niemeier, Sebastian Ocklenburg, Ayelet Sapir, Mark Tant, Nicole Thomas, Rachel Tomer, Daniel Voyer, and Laure Zago. Llewelyn Morris, Elfyn Roberts, David Robinson, and David McKiernan constructed the bespoke rear-projection short throw projector system used in Experiment 1. We are happy to share our colourscales stimuli and our emotional dichotic listening stimuli as executable scripts: interested parties please email [email protected] or [email protected]. Emma Karlsson was supported by a Bangor University School of Psychology PhD Scholarship. Leah Johnstone was supported by a Bangor University 125 Anniversary Scholarship. This research has been supported in part by a Leverhulme Trust research grant (RPG-2019-102) to D.P.C.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

David P. Carey http://orcid.org/0000-0001-8860-9731

Additional information

Funding

This work was supported by Leverhulme Trust [grant number RPG-2019-102].