Some exposure duration effects in simple reaction time

Studied simple reaction time (RT) as a function of exposure duration in 3 successive conditions using 4 trained university students: (a) foveal stimulation-target luminance constant, (b) nonfoveal stimulation-target luminance constant, and (c) foveal stimulation-target luminance randomly but slightly varying. Evidence was found for a critical duration beyond which RT increased with exposure duration in both foveal conditions. Within the critical duration, RT tended to obey Bloch's Law (intensity-time reciprocity). Increase in RT past the critical duration is analogous to the Broca-Sulzer effect noted in brightness and detection studies. Critical duration was greater when luminance was varied rather than held constant. With nonfoveal stimulation, RT was a monotonic function of exposure duration, i.e., no critical duration nor Broca-Sulzer effect was obtained. However, the failure to obtain the latter 2 effects may have been an artifact of the greater spatial uncertainty in the nonfoveal condition and not retinal locus per se. (PsycINFO Database Record (c) 2006 APA, all rights reserved).