Silberberg, A., & Fujita, K. (1996).
Pointing at smaller food amounts in an analogue of Boysen and Berntson's (1995) procedure.
Journal of the Experimental Analysis of Behavior,
66, 143-147.
Boysen and Berntson (1995) showed that apes could not learn to
point to a small amount of candy in order to get a larger amount
when pointing to the larger amount was reinforced by receipt of
the alterna te, smaller amount. They explained this result as an
unlearned predisposition to reach for higher value foods that
overrides the effects of reinforcement. This report tests their
thesis. In the first condition, 3 monkeys chose between one
raisin held in one hand by the experimenter and four raisins held
in the other hand. If a monkey pointed at four raisins, it
received one. If it pointed at one, it received four. Over ten
20-trial sessions, no monkey learned to point at the one-raisin
alternative, a result similar to that of Boysen and Berntson. In
the second condition, pointing at one raisin still produced four;
however, pointing at four raisins now produced no reinforcement.
In five 20-trial sessions, all monkeys learned to point at one
raisin in order to get four. This finding demonstrates that at
least in monkeys there is no predisposition to reach for higher
value foods that cannot be readily overridden by reinforcement
contingencies, and casts doubt on Boysen and Berntson's claim to
have demonstrated such a process in apes.
Key words: choice, maximizing, differential reinforcement,
monkeys