Reaction Time

Reaction Time

Reaction speeds are timed using a computerized visual stimulus generator for the letter A for the visual choice and the letters A and S for the two-choice as previously described (1,2), from the appearance of the letter to cancellation. Touching the corresponding key on an A and S keypad (Neuro-Test Inc., Pasadena, CA) stops the clock. Subjects are seated comfortably before a 65 cm tall table with eye to screen and keypad distances of 55 and 50 cm in a room at 22( C with subdued lighting. The computer clock recorded the time from flashing the letter on the screen until a key pressed. Pseudorandom numbers determined the stimulus order for choice (visual two-choice) reaction time and latency between succeeding letters which varied from 3-9 seconds. The 0.8 cm high 14x6 cm keypad instrument yields slightly faster measurements than those from an earlier computer keyboard version (1,2).

Two blocks of 20 trials for simple reaction time (SRT) permitted 13 practice trials the median of the final 7 trials as SRT for each subject is scored. After a brief rest, two 20 response trials are made for choice reaction time (CRT). The lowest median of the last 7 from the two trials is reported as the natural logarithm (Lg). Thus, irrespective of sequence, the fastest median (minimal time) is chosen.

Reference Notes:

1. Miller JA, Cohen GS, Warshaw R, Thornton JC and Kilburn KH: Choice (CRT) and simple reaction times (SRT) in laboratory technicians factors influencing reaction times and a predictive model. Am J Ind Med 1989;15:687-697.
2. Kilburn KH, Warshaw RH and Thornton JC: An examination of factors that could affect choice reaction time in histology technicians. Am J Ind Med 1989;15:679-686.