Fig. 1.

Illustration of the experimental (left) and control (right) conditions in Experiment 1. Both conditions began with two orientation trials (a), during which a box moved back and forth at the center of the apparatus floor. During the four familiarization trials (b), a cone stood near the right side of the apparatus, and a cylinder stood near the left side (in the control condition, only the cone was present). The box moved toward the cone, stopped against it, and remained in that position until the trial ended. Prior to the static display trial (c), the positions of the cone and cylinder were reversed (in the control condition, the cone was moved to the left side of the apparatus, and the cylinder was added on the right side); the box was absent during this trial. Two test trials followed. In the new-goal event (d), the box moved to the right and stopped against the cylinder; in the old-goal event (e), the box moved to the left and stopped against the cone.