Abstract
When humans forage for multiple targets in the succession of ‘patches,’ the optimal strategy is to leave the patch when the instantaneous rate of return falls below the average rate of return (Marginal Value Theory: Charnov, 1976). Human behavior has been shown to be, on average, near optimal in basic foraging tasks. Suppose, however, that foragers are allowed to return to previously foraged patches. What strategy would the foragers take when they revisit patches that they left previously, either compulsorily or voluntarily? Our computer-screen patches contained “ripe” and “unripe” berries, each defined by overlapping color distributions (d’ = 2.5). Observers attempted to collect ripe berries as fast as possible. One group of observers was forced to leave each patch after 10 seconds and then brought back to forage those patches for an additional 5 minutes. A second group foraged and moved to new patches when they wished to, before being brought back to pick the “leftovers” for 5 minutes. A control group foraged at will with no revisiting. The observers who were forced to leave the patches behaved like control observers, continuing where they left off when brought back to the patch and ending at about the same rate. Observers who had already voluntarily left a patch did continue to pick when brought back to the patch. However, the patches having been depleted, that picking was less productive. There appeared to be a small jump in the rate of foraging when these observers returned to their patches. It would be interesting to see if those observers would have bothered to pick on the second visit if they were not required to do so.