Investigations of closure processes: what source-monitoring judgments suggest about what is "closing"

On many occasions, the perception of an object is based on incomplete information because portions of the object are occluded from view. Nevertheless, people are able to identify an occluded object, suggesting that the identification is mediated by the activation of completion processes which "fill in" the missing information. Although these completion processes are invoked as causal mechanisms for many phenomena, the processes mediating the "completion" have not been specified. The present experiments tested two potential explanations for closure processes. In each experiment, participants were presented with pictures, complete or incomplete in form, and, on a surprise source-monitoring task, they were then asked to remember whether pictures had been presented complete or incomplete in form. Whether viewing pictures of objects, faces, or camouflaged objects, participants showed a pronounced tendency to claim that incomplete pictures were actually presented complete in form. This bias was evident after the participants described functions for objects (Experiments 1, 1A, and 2), after they evaluated properties of faces (Experiment 4), and after they searched for objects hidden in a complex scene (Experiment 5). However, this bias was not evident after they simply named objects portrayed in pictures (Experiment 3). This bias is interpreted as evidence for the activation of implicit imaginal processing. The results of these experiments are informative in their contribution to our understanding of the bases of closure, an intuitively appealing notion frequently invoked to account for object identification, but, as yet, not fully understood.