  A model of the mechanisms underlying exploratory behaviour, based on
empirical research and refined using a computer simulation, is presented. The
behaviour of killifish from two lakes, one with killifish predators and one
without, was compared in the laboratory. Plotting average activity in a novel
environment versus time resulted in an inverted-U-shaped curve for both groups;
however, the curve for killifish from the lake without predators was (1)
steeper, (2) reached a peak value earlier, (S) reached a higher peak value, and
(4) subsumed less area than the curve for killifish from the lake with
predators. We hypothesize that the shape of the exploration curve reflects a
competition between motivational subsystems that excite and inhibit exploratory
behaviour in a way that is tuned to match the affordance probabilities of the
animal's environment. A computer implementation of this model produced curves
which differed along the same four dimensions as differentiate the two
killifish curves. All four differences were reproduced in the model by tuning a
single parameter: the time-dependent component of the decay-rate of the
exploration-inhibiting subsystem.
