Position cues and reward memories as compatible components of serial learning

Rats were runway trained on three-trial series of different reward events, plain pellets (P), sucrose pellets (S), and nonreward (N). The series were constructed so that the position of the N event was always a valid cue for N. The relative validity of the P and S events, and their respective memories as cues, was manipulated by holding the reward kind constant, PSN or SPN (Experiment 1) and SNS and PNS, or SNP and PNP (Experiment 2), or by varying the reward kind from series to series (PSN, SSN, PPN, and SPN; Experiment 1). In both experiments, transfer tests to series with equivalent numbers of nonreward trials (NNN) or reward trials (SSS or PPP) showed that the pattern of approach, fast on P and S trials and slow on N, that developed under all training conditions was retained in the transfer tests. The transfer results implicate control by position cues under conditions that might otherwise have been interpreted only by reference to reward memories. (C) 2000 Academic Press.