INTERMANUAL TRANSFER OF SOMATESTHETIC INFORMATION - A 2-POINT DISCRIMINATION EXPERIMENT

Twenty-four men and 24 women, all university students, judged whether two-point aesthesiometric applications, either both to the same palm ( intramanual condition) or one to each palm (intermanual condition) wer e of the ''same'' or ''different'' spans. The main question was to det ermine the extent to which there is a loss of accuracy during interman ual comparisons, and by inference, interhemispheric relay. A second qu estion, the extent to which this loss is a function of the difficulty of the task, was to be answered by the inclusion of span-differences a bove, at, and below threshold. Difficult trials were associated with a highly significant intramanual advantage of 4.74%, and easy trials wi th a non-significant intramanual advantage of 1.16%. For both intra- a nd intermanual conditions, subjects made more errors aa function of de creasing ''span-difference''. The two hands performed equally well, an d the order of stimulation between the two hands made no difference in the results. The intramanual advantage could not be construed as an e ffect of response set (i.e., an artefact of subject's inherent bias fo r ''same'' or ''different'' judgements), nor as a scaling effect (e.g. , of span scales relating to receptive field properties, relating in t urn to interhemispheric relay). There was no evidence of a sex differe nce in basic ability, nor in the cost of hemispheric relay. It was con cluded that there is a loss of precision in interhemispheric relay of somaesthetic discrimination, but this can only be detected close to th reshold. Copyright (C) 1996 Elsevier Science Ltd.