Non-Random Sequences in Visual Threshold Experiments

Abstract

Responses (i.e. “seen” or “not seen”) to a repeated stimulus of constant intensity are shown to be grouped in runs of the same response. It is suggested that there are only two possible explanations of this non-randomness: spontaneous fluctuations of threshold and the direct influence of a response on succeeding responses. Experiments designed to distinguish between these two explanations have shown that the latter is the more important and that a response affects directly, though with diminishing intensity, the three immediately following responses.