Persistent preference in concurrent-chain schedules.

Abstract

Twelve pigeons, eight naive 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. Keywords: choice, persistence, preference, concurrent-chains schedules, pigeons ********** Given two response alternatives where one reinforcement rate is higher (rich) relative to the other (lean), behavior is allocated toward the richer alternative (Hernstein, 1970). That is, behavior is allocated between concurrently available sources of reinforcement so as to match the relative rates of reinforcement obtained from those alternatives. In addition, it has been shown that preference exists for variable over fixed schedules or reinforcement (Ahearn, Hineline, & David, 1992; Field, Tonneaau, Ahearn, & Hineline, 1996), and for the smaller ratio in concurrent variable-ratio (VR) schedules (Hernstein and Loveland, 1975; MacDonall, 1988; McMillan, Hardwick & Li, 2002). There is considerable evidence suggesting that prior conditions effect later performance. Using human subjects, Weiner (1964, 1969) found that responding under identical FI schedules differed as a function of previous schedule exposure. Specifically, response rates during a FI condition were similar to either a low or high response rate previously produced by either a fixed-ratio (FR) schedule or differential-reinforcement-of-low-rate (DRL) schedule. Additionally, research conducted by LeFrancois and Metzger (1993) provided further support for the influence of history on later responding. They trained rats to lever press under a DRL schedule before changing to a FI schedule of reinforcement. With a second group of rats, lever presses were trained first under a DRL schedule and later shifted to a FR schedule, before a FI schedule was put in place. Low rates of responding during the FI condition were only found with the first group of rats where the DRL immediately preceded the FI condition, suggesting that immediate history had more of a direct influence on FI responding than remote history in this case. Similar effects of schedule history can be found in research by Cohen, Perdersen, Kinney & Myers (1994), Urbain, Poling, Millam, & Thompson, (1978), Freeman & Lattal (1992), and Wanchisen, Tatham, & Mooney. (1989). An important question involves persistence after changes in reinforcement schedules. Research by Poppen (1982) with young adult university students involved lever pressing producing points programmed on a concurrent schedule. After training with one set of concurrent schedules, all subjects were shifted to a second schedule with different response requirements. The investigations showed that for many of the schedules, naive subjects performed differently than subjects with prior histories. …