FREE-CHOICE PREFERENCE WHEN ONE ALTERNATIVE IS RARELY OR NEVER CHOSEN

Abstract

In free choice, two or more responses eligible for reinforcement are concurrently available, as when a pigeon’s pecks on either of two keys can produce fixed-interval (FI) reinforcers. In forced choice, only one eligible response is available, as when pecks on one key can produce FI reinforcers but extinction (EXT) is arranged for pecks on a second key. Free choice is typically preferred when pitted against forced choice in terminal links of concurrent-chain or multiple concurrent-chain schedules. When multiple concurrent-chain schedules arrange conditions A and B respectively for left and right terminal links during one initial-link stimulus but their reversal during a second initiallink stimulus, preferences can be determined within sessions as differences between relative initial-link rates. The experimental question was whether free-choice preference is demonstrable even with one free-choice alternative rarely or never chosen. A history of multiple concurrent-chains with equal single-FI terminal links was followed by training, independent of initial links, of FI 20-s (green key), FI 40-s (yellow key), and EXT (red key). Multiple concurrent chain schedules then pitted free-choice terminal links with green (FI 20-s) and yellow (FI 40-s) keys against forced choice terminal links with green (FI 20-s) and red (EXT) keys. These terminal links maintained responding almost exclusively on the green key whether the other key was yellow or red, and all reinforcers were produced by green-key responding. Even with reinforcers equal and with the yellow alternative rarely or never chosen, the green-yellow terminal link (free choice) was preferred to the green-red (forced choice) terminal link.