Peripheral area-intensity interaction in scotopic visual reaction time

Two observers performed simple reaction-time responses to peripheral stimuli of varying intensity (-2.5 to +1.0 log td) and angular subtense (10 to 210 min). The area-intensity combinations that produced each of three scotopic reaction-time criteria were calculated. Analysis of these combinations showed that the area-intensity reciprocity could not be predicted by traditional theories of spatial summation. Like earlier findings for peripheral photopic reaction-time criteria, the results indicated that for small stimulus sizes, area has a greater effect than intensity in determining the scotopic reaction-time responses.