Incubation benefits only after people have been misdirected.

Incubation refers to the popular idea that stopping work on a problem may, at times, be a more efficient means by which to reach a solution than continuing to work. Empirical studies of incubation have used few participants and have provided ambiguous and discrepant results. We investigated three potential accounts of incubation in retrieval and search problems (subconscious work, spreading activation, and fixation forgetting) with the help of a large Internet-based participant pool. The amount of time allotted for explicit work on each of 12 problems was controlled, while the distribution of that time was manipulated in several incubation conditions. When problems were presented by themselves, none of the incubation conditions aided in the solution of either anagram or remote associate test problems. However, incubation benefits arose when participants were given misdirecting clues (probably because time delays facilitated forgetting of these clues).

Role of a circle's center in visual interpolation.

Basic geometric patterns like straight lines and circles seem fundamental to human perception and mental imagery. In this study we examined subjects' ability to interpolate circular curves-to derive the whole circle from an arc of 180 degrees or less. Specifically, we tested how the center point is utilized during such visual interpolation. Naturally, a mechanism that interpolates by extending the curvature of the visible arc will be unaffected by the presence or absence of the center point. On the other hand, a mechanism that achieves the same end by completing the circle from estimates of the center and radius will be significantly aided by the presence of the center. We found that when the visible arc was long (180 degrees), presenting the circle's center did not affect the precision with which subjects localized the invisible section. However, when the visible arc was relatively short (90 degrees or 45 degrees), displaying the center point significantly increased spatial precision. Thus, both computational mechanisms appear to exist.