Second-order texture contrast resolves ambiguous apparent motion.

When a black and a white square on a grey surround exchange places, it was previously shown that on a dark surround it is the white square, and on a light surround it is the black square, that is seen in apparent motion (AM). Thus the higher-contrast square carries the AM. We now show that the same is true for second-order AM of texture-defined squares. Squares were defined by four different textures: by anisotropy (horizontal versus vertical random dashes), by alpha numeric letters, by hash marks, or by dot size. The result was that the square that differed more from the surround in texture properties carried the second-order AM. Judgments of texture salience revealed a high correlation between salience and apparent motion. In a third experiment, crossover AM between dissimilar textures was investigated, and it was found that the more salient textures carried the AM. Results cannot be explained by the concept of "texture activity', but instead indicate that the system extracts a measure of "texture contrast' prior to analysis of salience and apparent motion.