Phenomenal Simultaneity and the Perceptual Moment Hypothesis

Successive brief visual stimuli falling within a critical time interval are phenomenally simultaneous. This paper examines two models of perceptual sampling which purport to account for phenomenal simultaneity. The first is Stroud's (1955) theory that the sensory input is quantized into successive, discrete summation periods or ‘moments’ (the Discrete Moment Hypothesis). An alternative model which has not generally been considered represents the ‘moment’ as a continuous, running sample of the input (the Travelling Moment Hypothesis). Two experiments on phenomenal simultaneity are reported which provide a critical test between these two hypotheses. The results were entirely incompatible with the discrete moment model, which is therefore rejected. The travelling moment model accounted well for the results. These also suggest a possible relation between the limits of phenomenal simultaneity and the critical duration of brightness summation.