Preference for free choice over forced choice in pigeons.
In a six-key chamber variable-interval initial links of concurrent-chain schedules operated on two lower white keys. Terminal links operated on four upper keys; green keys were correlated with fixed-interval reinforcement and red keys with extinction. Free-choice terminal links arranged three green keys and one red key; forced-choice terminal links arranged one green key and three red keys. Thus, terminal links were equivalent in number, variety, and information value (in bits) of the keylights. Preferences (relative initial-link rates) were studied both with location of the odd key color varying over successive terminal links and with the odd color fixed at key locations that had controlled either relatively high or relatively low terminal-link response rates. Free choice was consistently preferred to forced choice. Magnitude of preference did not vary systematically with terminal-link response rate or stimulus control by green and red keys. The origins of free-choice preference could be ontogenic or phylogenic: organisms may learn that momentarily preferred alternatives are more often available in free than in forced choice, and evolutionary contingencies may favor the survival of organisms that prefer free to forced choice.