Fig. 1 Effects of hypothalamic lesions in hooded rats on threshold of defence behaviour in the shock box (a) and the persistence of territorial behaviour in home cage (b). Defence behaviour was defined as defensive upright posture and boxing by both members of pairs of lesioned rats. Territorial fighting was defined as the presence of offensive side posture or full attack posture with biting, and it was quantified by the number of minutes during a test session in which one or the other behaviour was exhibited by the rat in his home cage against an intruder. Pre-operative data were not obtained in the shock box because of an interaction between the shock box and territorial testing procedures. One set of data was obtained from normal animals and is shown on the top line, together with post-operative data from sham-lesion rats. Closed circles - Pre-operative testing; open circles - post-operative testing.