Relative reward effects on operant behavior: Incentive contrast, induction and variety effects

Abstract

Comparing different rewards automatically produces dynamic relative outcome effects on behavior. Each new outcome exposure is to an updated version evaluated relative to alternatives. Relative reward effects include incentive contrast, positive induction and variety effects. The present study utilized a novel behavioral design to examine relative reward effects on a chain of operant behavior using auditory cues. Incentive contrast is the most often examined effect and focuses on increases or decreases in behavioral performance after value upshifts (positive) or downshifts (negative) relative to another outcome. We examined the impact of comparing two reward outcomes in a repeated measures design with three sessions: a single outcome and a mixed outcome and a final single outcome session. Relative reward effects should be apparent when comparing trials for the identical outcome between the single and mixed session types. An auditory cue triggered a series of operant responses (nosepoke-leverpress-food retrieval), and we measured possible contrast effects for different reward magnitude combinations. We found positive contrast for trials with the greatest magnitude differential but positive induction or variety effects in other combinations. This behavioral task could be useful for analyzing environmental or neurobiological factors involved in reward comparisons, decision-making and choice during instrumental, goal-directed action.

Striatal Activity and Reward Relativity: Neural Signals Encoding Dynamic Outcome Valuation

“…This result is exactly what was predicted for positive contrast, with faster response times in the mixed session compared with the single-outcome session. As found in previous work (Webber et al, 2015), we also had significantly shorter latencies for the alternative outcome during the mixed session in all three positive-contrast session types [low outcome (vs high), z = −2.201, p = 0.028; medium outcome (vs high), z = −2.19, p = 0.02); and medium outcome (vs low), z = −2.27, p = 0.01]. This latter effect could depend upon outcome generalization within the mixed session, leading to faster responses for each outcome during this testing period.…”

“…We obtained diverse relative reward effects on behavior. Positive and negative-contrast effects were obtained as well as other incentive value relations (Webber et al, 2015). …”

“…We have used the term “variety” to describe context-dependent activity and found that this form of activity did appear selectively during the mixed-outcome sessions (Webber et al, 2015). Most dramatically, the activity appears as uniform responses that are selective for the mixed session.…”

“…Variety effects can involve dishabituation and contrast to reduce sensory-specific satiety, and invigorate food consumption and operant responding for food (Bouton et al, 2013; Thrailkill et al, 2015). Another generalization effect on behavior was obtained that appeared as a transfer of value from one outcome to another (Webber et al, 2015). This process is similar to an effect-labeled induction, which is typically seen as an increase in responding for a less valued relative outcome and the degree of change is directly related to the relative value of the paired alternative higher valued outcome (Segal, 1972; Weatherly et al, 2001).…”

“…An example of general context effects would be variety influences, with possible incentive value shifts depending upon more or less variety within a situation (Webber et al, 2015). Variety effects are defined as enhanced responding when animals are exposed to diverse sets of alternatives compared with exposure to repetitive identical items (Thrailkill et al, 2015).…”