Cue competition as a retrieval deficit

Abstract

Four experiments using rats as subjects investigated the claim of Williams (1996) that cue competition results from an associative acquisition deficit, rather than a performance deficit. In Experiment 1, extinction of an overshadowing stimulus following overshadowing treatment increased responding to the overshadowed stimulus, thereby replicating prior observations with new parameters. In Experiment 2, an overshadowed stimulus failed to support second-order conditioning unless the overshadowing stimulus received prior extinction treatment. Experiment 3 replicated the recovery from overshadowing effect seen in Experiment 1 using a sensory preconditioning procedure. Most important, in Experiment 4 an overshadowed stimulus failed to block conditioned responding to a novel CS, but blocking by the overshadowed cue was observed following posttraining extinction of the overshadowing stimulus. These results, as well as those of Williams, are discussed in terms of traditional and more recent acquisition-focused models as well as an extension of the comparator hypothesis ( Denniston, Savastano, & Miller, 2001). CUE COMPETITION AS A RETRIEVAL DEFICITStudents of associative learning have long been interested in the conditions under which conditioned stimuli (CSs) trained together will compete with one another for behavioral control. One example of cue competition is the so-called "blocking" effect (Kamin, 1968). In a typical blocking experiment, a CS (A) is paired with an unconditioned stimulus (US) in Phase 1 (i.e., A→US); then in Phase 2, CS A and another stimulus (CS X) are paired with the US (i.e., AX→US). Blocking is evidenced by reduced behavioral control by CS X relative to subjects that received Phase 1 training with an irrelevant stimulus (i.e., B→US). Most contemporary theories of learning explain blocking and other forms of cue competition as a deficit in acquiring an X-US association. For example, Rescorla and Wagner (1972) explained blocking as a result of CS A accruing much of the associative value supportable by the US during Phase 1. This strong A-US association leaves less potential associative strength to the US available for assignment during Phase 2 than if both A and X were novel at the time of Phase 2 training.

When more is less: Extending training of the blocking association following compound training attenuates the blocking effect

“…The present results might be viewed as closely related to the prevention of blocking that is achieved by the blocking CS being, in turn, overshadowed (e.g., Denniston, Savastano, Blaisdell, & Miller, 2003). Specifically, Denniston et al (2003) found that AX-O trials prior to XY-O trials prevented X from overshadowing the target CS (i.e., CS Y).…”

“…Specifically, Denniston et al (2003) found that AX-O trials prior to XY-O trials prevented X from overshadowing the target CS (i.e., CS Y). In their Experiment 4, as in the present experiments, the potential of the first-order comparator (i.e., CS X in Denniston et al's [2003] experiment and CS A in our experiments) as a down-modulator of responding to the target CS (i.e., CS Y in Denniston et al's [2003] experiment and CS X in our experiments) was impaired by the second-order comparator (i.e., CS A in Denniston et al's [2003] experiment and the context in our experiments).…”

Overshadowing as a function of trial number: Dynamics of first- and second-order comparator effects

“…To the extent that Links 2 and 3 have robust comparator stimuli themselves, their potential to down-modulate responding supported by Link 1 is attenuated, and net responding elicited by the target CS should be increased. As is true of first-order comparator stimuli, second-order comparator stimuli can be discrete (e.g., Denniston, Savastano, Blaisdell, & Miller, 2003), or they can be contextual (e.g., Blaisdell, Bristol, Gunther, & Miller, 1998). Importantly, each stimulus other than the target cue and outcome can function both as a first-order comparator stimulus (which may be down modulated by second-order comparator stimuli) and as a second-order comparator stimulus (which may downmodulate other first-order comparator stimuli).…”

Challenges Facing Contemporary Associative Approaches to Acquired Behavior

“…Such phenomena are collectively called retrospective revaluation. Increases in responding to the target cue as a result of posttraining deflation of a companion stimulus are relatively easy to obtain (e.g., Denniston, Savastano, Blaisdell, & Miller, 2003), but a few failures to obtain the effect have been reported (e.g., Holland, 1999) suggesting that this effect like most effects is parameter dependent (Shevill & Hall, 2004). In contrast, decreases in responding to a target cue as a result of posttraining inflation of a companion stimulus is rarely observed when the target cue signals a biologically significant outcome such as food or footshock (e.g., Grahame, Barnet, & Miller, 1992;Miller, Hallam, & Grahame, 1990), but can be observed if the procedure is embedded in a sensory preconditioning procedure so that the target cue does not have the opportunity to control behavior until after the inflation treatment is complete.…”