Choice in a Variable Environment: Effects of Unequal Reinforcer Distributions

Abstract

Six pigeons were trained in a procedure in which sessions included seven unsignaled components, each offering two pecking keys, and each providing a potentially different reinforcer ratio between the two keys. Across conditions, various combinations of reinforcer ratios and reinforcer-magnitude ratios were used to create unequal reinforcer distributions between the two alternatives when averaged across a session. The results extended previous research using the same basic procedure that had included only reinforcer distributions symmetrical around 1:1. Data analyses suggested that the variables controlling choice operated at a number of levels: First, individual reinforcers had local effects on choice; second, sequences of successive reinforcers obtained at the same alternative (continuations) had cumulative effects; and, third, when these sequences themselves occurred with greater frequency, their effects further cumulated. A reinforcer obtained at the other alternative following a sequence of continuations (a discontinuation) had a large effect and apparently reset choice to levels approximating the sessional reinforcer ratio.

Global undernutrition during gestation influences learning during adult life

“…As in previous research using this procedure (Davison & Baum, 2000;Landon & Davison, 2001;Landon et al, 2003), data from the last 35 sessions of each condition were used in the analyses.…”

“…This pulse is followed by a movement toward indifference, at least when the overall sessional numbers of reinforcers are the same on both alternatives (as in the present experiment; cf. Landon et al, 2003).…”

“…Previous research using this procedure has highlighted the particular importance of sequences of reinforcers obtained at the same alternative (Davison & Baum, 2000Landon & Davison, 2001;Landon et al, 2003). In order to provide an overall measure of preference for the alternative at which the reinforcer was just obtained, log response ratios after right-alternative reinforcers were multiplied by 1 and then averaged with log response ratios after left-alternative reinforcers.…”

“…In the present research, we used a concurrent-schedule procedure introduced and reported on extensively by colleagues (e.g., Davison &Baum, 2000, 2002;Landon & Davison, 2001;Landon, Davison, & Elliffe, 2003). This procedure has been used to examine the speed of learning in pigeons under a range of variable environments.…”

Examining the Discriminative and Strengthening Effects of Reinforcers in Concurrent Schedules

“…One often‐obtained regularity is the preference pulse . immediately after a reinforcer, choice tends to favor the just‐productive alternative before settling at a level representative of the overall distribution of reinforcers (Davison & Baum, 2002; Landon, Davison, & Elliffe, 2003; Menlove, 1975). This short‐lived postreinforcer preference (both its magnitude and its duration) varies in subtle and informative ways related to experimental manipulations (Elliffe, 2006).…”