Persistent preference in concurrent-chain schedules.

Abstract

Twelve pigeons, eight naïve and four with a history of choice between different variable interval Schedules were exposed to concurrent-chains schedules to examine the effect of history on choice patterns. The initial links were always fixed-interval (FI) 3s schedules, and the terminal links were 5-valued variable-ratio (VR) schedules that varied by condition. During baseline, terminal link requirements were identical VR 60 schedules (equal alternative conditions) for both the red and white keys, producing indifference in all but one instance. Preferences were established by making the response requirements larger or smaller (depending on the condition) on the red key alternative (unequal alternative conditions). After preferences were established, 4 subjects were exposed to the equal alternative conditions, and 8 subjects were exposed to forced choice sessions with the same equal response requirements as during baseline before exposure to the equal alternative conditions. It was found that 10 of the 12 pigeons showed preferences that persisted during returns to baseline that were primarily influenced by either the immediately preceding unequal alternative condition or another particular unequal alternative condition. Two of the pigeons with prior histories did not show any shifts in preference with changes in terminal link response requirements.