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Hand posture, but not vision of the hand, affects tactile spatial resolution in the grating orientation discrimination task

French, Blandine; Di Chiaro, Nunzia Valentina; Holmes, N. P.


Nunzia Valentina Di Chiaro

N. P. Holmes


The grating orientation discrimination task (GOT) is a sensitive and reliable measure of tactile spatial resolution, or acuity. We used the GOT in three experiments to investigate the effects of hand posture and hand visibility on spatial acuity. Participant sex and experimental design were also manipulated. Healthy adult participants received brief touches to their index fingertips of grated, domed objects. Their task was to decide whether the gratings ran 'along' or 'across' their finger. Measures of the smallest grating width for which participants could reliably discriminate between orientations were recorded as threshold. Experiment 1 evaluated the effect of two- versus one-interval discrimination, hand used and participant sex. Experiments 2 and 3 evaluated the effects of hand visibility (visible or covered) and hand posture (in front or to the side). Females were better than males; the two-interval task resulted in lower thresholds than the one-interval task; and left and right hand thresholds were not significantly different. Most importantly, while hand visibility did not have a significant effect on the task, thresholds were affected by hand posture—worse when the hand was oriented to the side of the body than in front. These results replicate previously reported effects of sex (or finger size), but failed to replicate the so-called ‘visual enhancement of touch’ (VET) effect. We also report a meta-analysis of 27 VET studies, finding a significant effect of ‘non-informative’ vision on tactile perception. Our novel finding is that hand posture affects tactile acuity.


French, B., Di Chiaro, N. V., & Holmes, N. P. (2022). Hand posture, but not vision of the hand, affects tactile spatial resolution in the grating orientation discrimination task. Experimental Brain Research, 240, 2715-2723.

Journal Article Type Article
Acceptance Date Aug 24, 2022
Online Publication Date Sep 8, 2022
Publication Date 2022-10
Deposit Date Aug 24, 2022
Publicly Available Date Sep 9, 2023
Journal Experimental Brain Research
Print ISSN 0014-4819
Electronic ISSN 1432-1106
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 240
Pages 2715-2723
Keywords General Neuroscience
Public URL
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