Detour Experiments with Split-brain Octopuses

Octopuses will make detours down an opaque corridor in order to reach crabs initially visible but not directly accessible to them (Wells, 1964). The situation can be used to investigate the function of parts of the brain in short-term learning and in interocular transfer. In a previous account the effects of removing the vertical lobe were considered. If this lobe is removed from the visual learning system, the proportion of errors (the octopus makes an error if it turns the wrong way at the end of the corridor—see Fig. 1) is increased. The effect is negligible if the octopus completes the detour within about 30 s, but rises sharply if runs take longer as a result of selfimposed or operator-imposed delays (see method below). Runs taking up to 2 min were usually made correctly by controls, while the operated animals made chance scores in detours taking longer than 1 min (Wells, 1967). The present account is of a further series of experiments extending the work on the visual system by using animals in which one side of the supraoesophageal brain was partly or wholly separated from the other by a longitudinal vertical cut. This technique allows one to draw conclusions about the function of the optic commissures and other structures in learning and in interocular transfer.