The effects of varying the interreinforcement interval on appetitive contextual conditioning

Abstract

Appetitive contextual conditioning in rats and ringdoves was investigated in six experiments. In Experiment 1, differential contextual training produced greater anticipatory activity in rats in the presence of a context paired with food than it did in rats in the presence of a different context in which food was never presented. Furthermore, the rats showed a preference for the context associated with food when they were given a simultaneous choice test between contexts. In Experiment 2, rats were more active in and preferred a context associated with a variabletime 30·sec (VT30) schedule as opposed to a VT180 schedule. Experiment 3 was a between-subjects replication ofthe previous experiment. As expected, rats exhibited significantly more anticipatory activity in a context in which food had been presented on a VT30 schedule than they did in a context in which food had been presented on a VT180 schedule. Experiment 4 showed that anticipatory activity was a reflection of context-US associations in ringdoves, and in Experiments 5 and 6, ringdoves also exhibited an inverse relationship between the amount of anticipatory activity and the length of the interreinforcement interval (lRI). These results reveal a relation between IRI and contextual conditioning opposite from that obtained in studies of aversive conditioning.Temporal variables exert a strong influence on associative learning (Gibbon & Balsam, 1981;Gormezano & Kehoe, 1981). Perhaps the best known example is the trial-spacing effect, in which aequisition of an association between a conditioned stimulus (CS) and an unconditioned stimulus (US) is facilitated by lengthening the intertrial intervals (lTIs; see Gormezano & Moore, 1969). Several different underlying mechanisms have been proposed to account for the trial-spacing effect.Variation in ITI may influenee aequisition by affecting US processing or effectiveness. The repeated presentation of the US may result in habituation, and sinee there is greater short-term habituation with shorter intervals between stimuli (Davis, 1970), the US may be relatively less effective when trials are massed rather than more widely spaeed. Yet even as this general predietion follows from aU theories of habituation, more specifie predie- tions ean be derived from partieular theories about how the effectiveness of a stimulus ehanges with repeated presentations. Solomon and Corbit (1974) suggest that reception of a US generates two opponent processes. For exarnple, an electrie shock releases a short-latency, rapid-decay primary process (the a process) of an aversive nature. The primary process gives rise to a long-latency, slow-decay secondary process (the b process) that opposes the aversive state. The effective motivational state of the subject is a function ofthe difference between the two processes. Since the secondary process is slow to decay, when I'I'ls are relatively short, the secondary process indueed on trial n -1 may decrease the motivational properties of the US presented on trial n. Assuming that the rapid-decay ...

Intertrial interval effects in pavlovian serial feature positive discriminations

“…For example, some authors (e.g., Mustaca, Gabelli, Papini, & Balsam, 1991) have suggested that shorter ITIs and, hence, higher rates of US presentation encourage greater context conditioning, which might in turn influence the effectiveness of various trial types in generating discrimination learning or performance. In opposite significance (e.g., Grant, 1975;Hogan et al, 1981;Pontecorvo, 1983) or generated a response that was incorrect for the present trial (e.g., Roitb1at & Scopatz, 1983).…”

Time to rethink the neural mechanisms of learning and memory

“…First, if a light comes on and remains on for a long time before the grain, the bird does not peck at it. Instead the bird becomes hyperactive and paces back and forth in the chamber(Mustaca, Gabelli et al 1991; Silva and Timberlake 2005). Thus a long CS does not result in a failure of learning; the learning is intact, but the way it is expressed changes based on the duration of the CS (see also(Holland 1980)).…”

Chemosensory conditioning in molluscs: II. A critical review

“…From this perspective, the conditioning paradigm may be construed as consisting of several extended "simultaneous" conditioning trials in which illumination and turbulence overlap (albeit their onsets were delayed by 7-8 sec). Although Talk et al justified their use of short US interstimulus intervals (ISIs) on the basis of findings with vertebrates that contextual conditioning is facilitated for massed versus distributed USs, the USs used in those studies (electric shock in Williams, Frame, & LoLordo, 1991; small rat chow pellets that were immediately consumed or 4-sec pigeon grain presentations in Mustaca, Gabelli, Papini, & Balsam, 1991) were brief and probably lasted little longer than their nominal presentation durations.…”