Hybrid visual and memory search for scenes and objects with variable viewpoints.

In hybrid search, observers search visual arrays for any of several target types held in memory. The key finding in hybrid search is that response times (RTs) increase as a linear function of the number of items in a display (visual set size), but RTs increase linearly with the log of the memory set size. Previous experiments have shown this result for specific targets (find exactly this picture of a boot on a blank background) and for broad categorical targets (find any animal). Arguably, these are rather unnatural situations. In the real world, objects are parts of scenes and are seen from multiple viewpoints. The present experiments generalize the hybrid search findings to scenes (Experiment 1) and multiple viewpoints (Experiment 2). The results replicated the basic pattern of hybrid search results: RTs increased logarithmically with the number of scene photos/categories held in memory. Experiment 3 controls the experiment for which viewpoints were seen in an initial learning phase. The results replicate the findings of Experiment 2. Experiment 4 compares hybrid search for specific viewpoints, variable viewpoints, and categorical targets. Search difficulty increases from specific viewpoints to variable viewpoints and then to categorical targets. The results of the four experiments show the generality of logarithmic search through memory in hybrid search.