Abstract
Using a concurrent-chains procedure, the present study examined preference of monkeys between forced-choice and free-choice with multiple alternatives. The forced-choice was followed by the reinforcer with a probability of .8. The free-choice was between reinforcement alternatives of high probability (p = .8) and low probability (p = .5) in which the monkeys mostly chose the former. The number of keys with each kind of alternative in the free-choice was manipulated under four conditions. Preference for free-choice increased with the number of keys for the preferred alternative. However, the number of keys for the less-preferred alternative had no influence on preference. Effects of the less-preferred alternative on preference were inconsistent with previous studies using pigeons.
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