The Influence of Preoperational Training On the Performance of Octopuses Following Vertical Lobe Removal

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Abstract
Blind octopuses were trained to discriminate between two objects by touch by taking one and rejecting the other. When they had learned to do this their vertical lobes were removed and postoperational survival of the effects of preoperational training was tested, either by continuation of training or by means of retention tests. When training was continued after vertical lobe removal animals pretrained at a rate of 8 trials per day for 48 or 96 trials reverted to taking both of the objects to be discriminated (as at the start of training), but subsequently relearned to dis-criminate between them with an accuracy approaching that of controls. They took fewer trials to learn after operation than animals that had not been pretrained. Animals pretrained at a rate of 40 trials per day for 120 trials showed little or no disturbance of learned responses as a result of the same operation. In retention tests carried out immediately after operation, animals pretrained for a similar number of trials at rates of 8 and 40 trials per day made more errors than controls, but showed, nevertheless, that the effects of pretraining by either method were not entirely lost as a result of the operation. These results are discussed in relation to the general problem of the interpretation of discrimination experiments which force animals to react ‘positively’ or ‘negatively’ in an all-or-nothing manner and thereby conceal differences in the degree to which memories are established. It is concluded that the effect of vertical lobe removal can be attributed to a reduction in the amount of tissue available for memory retention.