A Further Study of the Pendulum Phenomenon

A first series of experiments had demonstrated certain conditions eliciting or inhibiting a “pendulum” phenomenon in the visual perception of apparent movement. The present study consists of five further variations designed to show more clearly conditions of occurrence and non-occurrence of this type of movement. The main findings are: (1) Altering the axis of display to vertical significantly reduces the frequency of pendular-movement perception; (2) Altering the position of metronome from behind to the side of the visual display, gives results almost identical with those where the metronome was inaudible, but, when the metronome is illuminated in this position, all forms of movement perception are reduced, and no pendular movement is reported. The results for all the ten conditions, including the five of the first series are summarized, and the following possible factors are discussed: past experience, physiological nystagmus, and intervening adaptation. All three may be required to account for the perceptual phenomena under investigation and the dichotomizing of explanations into “experiential,” or “physiological,” appears to be arbitrary and inconsistent with the complexity of the observed facts.