Short-term learning and interocular transfer in detour experiments with octopuses.

Octopuses will make detours in order to reach prey that is not directly accessible to them. Using the apparatus shown in Fig. 1 Wells (1964) trained octopuses to make detours to reach crabs shown in the feeding compartments flanking the central corridor. Eight out of twenty-nine animals tested completed detours successfully on entering the corridor for the first time at their first trial. The remaining animals nearly all entered the corridor but failed to complete detours until they were shown a crab at the far end of the corridor and were led round into the feeding compartment. Thereafter most of the octopuses made detours reliably without intermediate inducements. Thus in 220 trials carried out with eleven animals, each run for twenty trials beginning with its first completed unled detour, 197 correct responses were made. There were only ten errors (occasions at which the octopus turned into the wrong feeding compartment) and thirteen failures to run (octopus had not reached a feeding compartment within 10 min of the start of the trial). The results from a variety of experiments (Wells, 1964) indicated that the detour was guided visually. Correct performance seemed to depend on the animals' fixating the wall on the goal side when it went into the corridor and searching along this for a gap. Animals trained to run by means of a series of trials all on one side performed correctly first time when tested by showing them a crab in the other feeding compartment, so that there would appear to be no question of their having learned to follow a particular sequence of visual, olfactory or tactile cues in the maze. Normally, a detour took 20 to 30 sec., but individuals varied and the best performers regularly completed their runs within 10 or 20 sec. of entering the corridor. The account that follows deals with the effect of imposed delays, during which the animals were shut into the corridor in the course of their detours. It is also concerned with the effect of removing the vertical lobe from the brain. The vertical lobe is known to be important in visual learning (Young, 1961, 1964) and its removal prevents interocular transfer in some visual discrimination experiments (Muntz, 1961 a-c).