Response-contingent variation in visual recall: evidence of a dynamic memory trace.

Sixty-six subjects learned responses to four ellipses (eccentrically 0.52) which varied orthogonally in area (two large: 994 mm2; two small: 671 mm2) and orientation (two with major axis vertical, two with major axis horizontal). Correct responses were contingent on either the area or the orientation of the ellipses. After learning the correct responses, subjects recalled the ellipses by drawing them. Recall was either immediately, 1 day, or 2 weeks after learning the responses. The recall drawings were measured for area and for orientation (ratio of the length of the vertical to the horizontal axis). Differences among the recall drawings increased on the dimension (area or orientation) which was associated with correct responses during the learning task. The differences on the associated dimension were large when recall was tested immediately after the response learning task, small when recall was tested 1 day after learning, and large again when recall was tested 2 weeks after learning the responses. This experiment eliminated one potential source of uncontrolled variability in earlier results. The results are consistent with previous experiments and suggest an active two-phase memory consolidation process extended over time.