1. Octopuses from which either the median superior frontal or the vertical lobes have been removed show reduced capacity to learn to attack an unfamiliar figure.
2. The duration of the increased tendency to attack after feeding is reduced by both operations. This suggests that the failure to learn is due to interruption of a self-re-exciting circuit.
3. Although these operated animals would not attack rectangles they continued to attack crabs for much longer than controls, in spite of shocks. They also retained signs of this inhibition less well.
4. When the median superior frontal lobe alone had been removed the remaining vertical lobe was able to exercise considerable restraint by virtue of its input from below.
5. This shows that the effect of this lobe in preventing attack at a particular figure cannot be wholly due to pre-synaptic inhibition, since the effect can appear when the relevant pre-synaptic fibres are absent. The ‘pain’ fibres are therefore able to activate the vertical lobe to produce inhibition of the system that produces attack at a particular shape.