Effects of early common features on form perception.

Recognizing forms may involve a contingency in which later processing is modified, depending on the results of early analyses. This hypothesis can be distinguished from feature models, in which features (including early global features) accumulate over time. In four experiments, shape primes were presented briefly, followed immediately and in the same location by a similarly or differently shaped target, and then a mask. Accuracy was measured with a two-alternative forced-choice discrimination. The primes facilitated discriminations between a similarly shaped target and differently shaped foil, as would be expected. More important is that the primes also facilitated discriminations between similarly shaped targets and similarly shaped foils, even though the primes contained only features common to the alternatives and thus provided no discrimination-relevant information. The facilitation effect was constant over variations in the size of the target set, the type of mask, and the type of baseline condition. This result is consistent with the idea of early-to-late contingencies in processing but was not predicted by feature models.