Figure 4.

Histograms of the mean time spent by the fish in each of three areas in the focal compartment of the experimental tank for each experimental condition. Error bars refer to the s.e. Means not sharing a common superscript are significantly different (Fisher's PLSD, p < 0.05). We note that for O, the ‘robot’ region refers to the left side of the tank and that such condition is not part of the statistics due to the arbitrariness in the selection of the juxtaposed stimuli. See the end of §2.5 for a description of experimental conditions. (Online version in colour.)