Testing the effect of report modality on psychophysical sensitivity yields inconclusive results

In the study of perception, motoric reports are the principal means by which subjective experience is experimentally inferred. A widely held and implicit assumption in such experiments is that the motor action conveys, but does not tamper with, perceptual experience. In a cross-over repeated measures design, we tested nine observers on a luminance detection task. In separate conditions, observers reported their detection via movements of either their hands or eyes. Using Bayesian statistics we found only anecdotal evidence for any modality-dependent difference in psychophysical sensitivity. In the context of several reports suggesting the existence of report-dependent perceptual effects, the anecdotal evidence offered here, unfortunately, does not shift credence in either direction. Thus more extensive sampling of this putative phenomenon is needed and encouraged.