Reaction time and critical duration for lines' detection and identification of their orientation

Reaction time (RT) and duration of complete temporal summation (tc) were studied for both detection of lines and identification of their orientation. The RT was studied as a function of stimulus intensity, number of orientations and angular difference between them. The temporal summation was studied for detection and identification at several angular differences. It was found that the intensity-dependent part of RT for identification at angular difference of 22 degrees equaled that for detection but considerably lengthened at smaller angular differences (10 degrees). The intensity-independent part of RT was minimal for detection and maximal for identification with eight alternatives. The tc increased from 30 msec for detection and identification with the accuracy of 22 degrees to 100 msec for identification with the accuracy of 5 degrees. The results support the conclusion that detection and coarse identification differ only in their later stages and that accurate identification involves additional processes with longer time-constants compared to coarse identification.