A SIMPLE LABORATORY DEMONSTRATION OF SUBCEPTION

A simple, replicable demonstration of subception is described, using a discriminatory response as the independent variable. Stimuli were exposed to thirty‐six subjects in a tachistoscope until they were able to report the perception of a black line, appearing in the centre of a white field. The subjects were then asked to choose one of two geometrical figures from six pairings of four figures, each pair shown separately. The tachistoscope projections, presented in a counterbalanced design, consisted of one of the figures to be discriminated drawn in red, divided by a 3 cm black line. The black line, having a stronger contrast, was perceived before the red figure, defining the supraliminal and subliminal thresholds as the contrast relation between red and black lines. A significant tendency was found for selection of the projected figures, without verbal report of the subliminal stimulus. In a second part of the experiment one figure was to be chosen, after each projection, from the finite population of four figures; the results did not differ from chance expectation. The use of a perceptual discriminatory response for the recovery of a subliminal stimulus was discussed, and the plausibility of a threshold for intensity relations was demonstrated.