Reversal of cubic and cylindric figures

Spontaneous figure reversal of ambiguous patterns was analyzed in humans by presenting "Necker-cube"-like, or "drum"-like figures having square or round shaped "front" and "rear" surfaces, and either large or small "depth". The figures were perceived alternately according to one or the other of two possible mental orientation-interpretations. The subjects signalled the instant of subjective pattern-reversals. Results: perceptual intervals corresponding to both interpretations of "drum" were longer than those of "cube"; the perceived "depth" of the figures was less relevant for reversal timing ("deeper" figures reversed only slightly more slowly and the corresponding intervals were somewhat longer). Although the shape of "front" and "rear" surfaces was not a crucial geometrical feature for representing the three-dimensional nature of the patterns on the two-dimensional stimulus plane, it markedly influenced the timing of figure reversals. More, or longer information processing steps should needed for perceptual-cognitive representations of curvilinear patterns in comparison with rectangular ones.