Ensemble size and selective response times with a constant signal rate

Using a selective response task in which subjects were required to respond only to one of a number of alternative digits, although signal rate was held constant, the latency of selective responses was found to lengthen as the number of alternatives increased. This finding does not support the inference drawn from the work of Mowbray (1960) that, with signal rate held constant, there should be no significant lengthening of reaction times as the ensemble of digits increases.