Figure 2.

A time-dependent preference for opaque internal corners. (A). An arena was constructed with two intersecting walls that generated four internal corners. (B). The mean time spent in the 4-cm² sector in the center of the arena was determined with four combinations of opaque internal and external vertical surfaces. In each case, the flies spend more time in the center zone in the arena with internal corners than the control open arena of the same size. When the outer wall was clear and the internal walls were opaque, the flies spent even more time in the center. (C). Only in this last experiment with the opaque internal corners, there was a significant interaction between mean percentage of time spent in the center and time in the arena (F₉₆₂₀ = 2.380, P = 0.012). This time dependence leads to an inverse relationship between amount of specific exploration and percentage of time spent in the corner. n = 32 for each arena.