Priming impossible figures in the object decision test: The critical importance of perceived stimulus complexity.

Previous research showed that object decision priming was found for possible, but not impossible, three-dimensional objects (e.g., Schacter, Cooper, & Delaney, 1990; Schacter, Cooper, Delaney, Peterson, & Tharan, 1991). We tested those objects and found that the impossible objects were subjectively more complex than the possible objects. We then constructed two sets of possible and impossible objects-one set that was equated for complexity, and one set that differed- for use in the object decision test. The results showed that when impossible objects were high in complexity and possible objects were low in complexity, priming was found only for possible objects; when possible and impossible objects were equated at a moderate level of complexity, priming was observed for both object types. These findings indicate that perceived object complexity, more than object possibility-impossibility, determined priming in the object decision test. The demonstration of object decision priming for possible and impossible objects calls for a reformulation of the structural description system explanation.