Necessary considerations for a theory of form perception: a theoretical and empirical reply to Boselie and Leeuwenberg (1986)

Boselie and Leeuwenberg (1986) recently defended their version of the minimum principle, called structural information theory or SIT, against a varied set of criticisms. Two of the most notable of these criticisms are (i) that perceptual organization can proceed as a piecemeal, rather than as a global, process (as demonstrated by partially-biased Necker cubes and 'impossible' figures), and (ii) that perceptual organization is influenced by subjective variables as well as by stimulus variables (Peterson and Hochberg 1983). The second criticism was acknowledged by Boselie and Leeuwenberg but not addressed. The first criticism was addressed by the introduction of two new variables into SIT in order to argue that the perceived organization of partially-biased Necker cubes and impossible figures can be predicted by a global coding scheme, thereby supporting rather than refuting global minimum principles. It is argued here that the criticisms cannot be dismissed by this rebuttal, which is focused narrowly on single examples rather than on the general principles embodied by the demonstrations. The implications of piecemeal perception and subjective mediation are spelled out, and both old and new data showing that the applicability of global minimum principles must be reexamined, not merely defended, are discussed. Finally, the argument for a richer, more interacting, theory of form perception is presented.