A correction and a comment on Craig and Lyle (2001)

In a recent paper, Craig and Lyle (2001) measured tactile spatial acuity on the palm and compared these results with the results from similar measures on the fingertip. The changes in sensitivity between the two sites appeared to be consistent with estimates of the relative density of innervation between the two sites. Rather than compare their results with changes in the density of innervation, Craig and Lyle should have compared them with changes in the spacing between receptors. On this basis, psychophysical performance is much poorer on the palm than one would predict on the basis of the spacing between receptors. Some possible reasons are offered for the difference between the psychophysical results and the predictions based on receptor spacing.