Response independent habituation of territorial aggression in the three-spined stickleback (gasterosteus aculeatus).

Territorial sticklebacks were habituated to a male conspecific confined to a clear glass tube in a two stage experiment. In the first stage, one group was allowed complete access to a stimulus tube containing a live, male conspecific and the number of bites directed at the stimulus was recorded. A second group was prevented from biting at the stimulus fish by placing a glass barrier between the territorial resident and stimulus tube. A third group was treated the same as the second but without a stimulus fish present. During the second stage of the experiment, which followed a 15 min rest, all groups were allowed access to the stimulus tube and confined conspecific. A typical habituation curve resulted across both sessions for the first group. The second group, which was characterized by very infrequent attempts to bite during state 1, showed behavior during stage 2 identical to that of group 1. During the second stage, the third group demonstrated typical initial habituation behavior (parallel to that of group 1 during the first stage). These results are interpreted as evidence that habituation proceeds as a function of exposure to a stimulus and is independent of whether or not a response is made.