Generation of random sequences by human subjects: A critical survey of literature.

The subjective concept of randomness is used in many areas of psychological research to explain a variety of experimental results. One method to study randomness is to have subjects generate random series. Unfortunately, few results of the experiments that used this method lend themselves to comparison and synthesis because the investigators employed such a variety of experimental conditions and definitions of mathematical randomness. Some suggestions for future research are made. In many different fields of psychological research, the concepts of subjective chance and subjective randomness have been used almost exclusively to account for unexpected results. Characteristic of subjective chance is that it is not equal to mathematical chance; subjects seem to expect dependencies between successive events in spite of the fact that they know that the events occur independently of each other. Early in this century, psychophysics became interested in this phenomenon or the fact that successive responses of a subject are mutually dependent. In the psychophysical setting, the usual procedure is that a binary choice is made. Particularly experienced subjects are well aware that they are supposed to choose the alternatives in a random order. Even so, the subjective chance phenomenon persists. Hence, one possible explanation of interdependency of responses is that the subject has his own idea of what a random sequence looks like. More recent research on subjective probability, probability learning, and gambling behavior also revealed that successive responses of a subject were mutually dependent in experimental settings where independent responses were expected. Once again the subjective concept of randomness was mentioned as an explanation. In experiments on telepathy the concept was used to account for too many correct predictions of serial events. Clinical psychologists