Behavioral contrast redux

Abstract

Contrastis a ubiquitousconceptin experimental psychology. Most well known are contrast effects with respect to sensory systems, exemplified by color and brightness contrast. In other areas of psychology, the concept of adaptation level has wide applicability. In all of these domains, the effect of a given stimulus value seemingly involves a comparison process such that the psychological impact of a stimulus is due not solely to its absolute value, but also to its value relative to that of other stimuli presented either in the same context or in the past. Although the empirical phenomenon of contrast is pervasive, whether it is regarded as a basic psychological process or, instead, is to be explained in terms of more fundamental mechanisms varies widely across different areas of psychology. REINFORCEMENT CONTRAST:A BRIEF HISTORYThe concept of contrast has played a major role in reinforcement theory, both in generating voluminous research and in posing theoretical challenges. There are two major classes of contrast, with relatively separate experimental literatures. Successivecontrast is said to occur when the level of behavior maintained by a given reward outcome varies with the nature of the reward outcome previouslypresented. The most well known example was reported by Crespi (1942). The running speeds in a straight alley of rats maintained on a constant level of reward amount were compared with those of other rats for which the same amount of reward was presented either after experience with a smaller reward or after experience with a larger reward. Subjects shifted from a smaller amount ran faster than subjects with the constant amount throughout, which Crespi labeled an elation effect, whereas rats shifted from a larger amount ran slower than those with the constant amount throughout, which was labeled a depression effect. As a result of these and similar findings, Hullian learning theory modified the concept of incentive(the K parameter) to become a performance variable, which ultimately made it difficult to distinguish the Hullian account from other competing accounts explicitly cognitive in nature. Successive contrast effects have continued to be investigated widely even with the decline in influence of Hullian learning theory, often in the context of physiological manipulations to assess their underlying basis. Because Flaherty (1996) has provided a comprehensive review of this literature, no further account will be provided here.The second type of contrast procedure is when the behavior produced by a constant reward payoff is affected by the reward conditionsthat are alternately presented for the same response under different stimulus conditions. This procedure is sometimes labeled simultaneouscontrast, a misnomer because the different reward conditions are not simultaneously present. However, the different conditions do occur in close temporal proximity, whereas in the successive contrast procedure the different reward conditions are often experienced with significant temporal separations. Although sim...

Failure to obtain value enhancement by within-trial contrast in simultaneous and successive discriminations

“…This view provides an intuitively appealing account of a wide range of phenomena known collectively as contrast effects (Flaherty, 1996;Williams, 2002). For example, a stimulus that is correlated with a given rate of reinforcement will maintain a higher response rate when the reinforcement rate correlated with an alternative stimulus is relatively low than when it is relatively high (Reynolds, 1961;Williams, 1983).…”

On the determinants of induction in responding for sucrose when food pellet reinforcement is upcoming

“…Second, because the procedure in which it is observed shares similarities with procedures that produce contrast, understanding why it occurs has the potential to shed light on the phenomenon of contrast. For example, if the inductionlike increase in responding occurs through Pavlovian processes, support would be provided for the view that contrast occurs despite, not because of, Pavlovian influences (Williams & McDevitt,2001; and see Williams, 2002).…”

“…Although it is possible that the increase in responding for sucrose occurs because of prospective factors (i.e., food pellets will be available later in the session), it is also possible that it occurs because of retrospective ones (i.e., food pellets were obtained in the previous session). Williams (1983Williams ( , 2002 has argued that steady-state behavioral contrast is largely, if not completely, controlled by prospective factors. Thus, if induction is also prospective, it is possible that contrast or induction occurs because of deviations in the same causal mechanism.…”

“…Much research has been conducted to determine under what conditions contrast will occur (see McSweeney & Weatherly, 1998). Beyond basic empirical findings, numerous theoretical accounts have been put forward in an attempt to explain when and why contrast occurs (see, e.g., Williams, 2002, for a review).…”

“…The first attributes the occurrence of contrast to procedural variations between conditions (e.g., McSweeney & Weatherly, 1998), the second attempts to identify general mechanisms that could lead to contrast (e.g., Hinson & Staddon, 1978), and the third invokes cognitive processes (see Williams, 2002, for a discussion of each type of explanation). Yet contrast remains intriguing for several reasons.…”