CRT screens may give rise to biased estimates of interhemispheric transmission time in the Poffenberger paradigm.

It has been shown that computer video-display units do not emit luminance uniformly over the entire screen, but emit more light on the right hand side than on the left hand side. The present study investigates whether this luminance asymmetry has implications for the manual and vocal estimates of interhemispheric transmission time (IHTT) in the Poffenberger paradigm. In particular, it is shown that previous reports of right visual-field advantages for vocal responses are an artifact of the luminance asymmetry of computer screens and that this asymmetry also has implications for estimates of differences in transmission time from the right to the left hemisphere in manual responses. In addition, we examined the impact of stimulus intensity and dark adaptation to the IHTT estimates and found that neither had an effect. This is in line with previous evidence that interhemispheric transfer in the Poffenberger paradigm does not depend on the transfer of visual information.