Reducing Pausing at Rich-to-Lean Schedule Transitions: Effects of Variable-Ratio Schedules and Noncontingent Timeouts

Transitions from relatively rich to lean conditions of reinforcement often produce extended pausing because this transition is relatively more aversive than other transition types (e.g., rich-rich, lean-lean, and lean-rich). In applied settings, aversive rich-lean transitions may underlie maladaptive aberrant behavior (e.g., self-injury, aggression, and severe stereotypy). Reducing the aversiveness of this critical transition is of basic and applied interest. The length of the pause may be used as an index of the aversive stimulation at rich-lean transitions and as an analog measure of aberrant behavior in clinical settings. Experiment 1 investigated the effects of arranging rich-lean transitions between variable-ratio (VR) schedules or random-ratio (RR) schedules on pausing at rich-lean transitions in four pigeons. Variable- and random-ratio schedules were equally effective at reducing pausing at rich-lean transitions. These results suggest that the aversive stimulation at rich-lean transitions was reduced with variable schedules. The applied implication is that aberrant behavior should be less likely to occur at rich-lean transitions when variable schedules are arranged. In Experiment 2, four transitions were separated by a timeout period imposed between the end of the reinforcer and before the start of the next multiple-schedule component. During the timeout, the response key was darkened and the reinforcement schedule was suspended until the timeout interval had elapsed. Across different timeout durations, ratio sizes, and probes, the timeout produced inconsistent within- and between-subject results. Inconsistent results may be attributable to the timeout reducing the number of transitions completed, performance failing to meet the quantitative and qualitative stability criteria, and insufficient reinforcement in the lean-schedule component. An interesting possibility raised by Experiment 2 is that the multiple schedule may have "chain-like" features (e.g., access to a rich-schedule component), which may maintain responding in the lean component when there is insufficient reinforcement

Aversive properties of negative incentive shifts in Fischer 344 and Lewis rats

Research on incentive contrast highlights that reward value is not absolute but rather is based upon comparisons we make to rewards we have received and expect to receive. Both human and nonhuman studies on incentive contrast show that shifting from a larger more-valued reward to a smaller less-valued reward is associated with long periods of nonresponding—a negative contrast effect. In this investigation, we used two different genetic rat strains, Fischer 344 and Lewis rats that putatively differ in their sensitivity to aversive stimulation, to assess the aversive properties of large-to-small reward shifts (negative incentive shifts). Additionally, we examined the extent to which increasing cost (fixed-ratio requirements) modulates negative contrast effects. In the presence of a cue that signaled the upcoming reward magnitude, lever pressing was reinforced with one of two different magnitudes of food (large or small). This design created two contrast shifts (small-to-large, large-to-small) and two shifts used as control conditions (small-to-small, large-to-large). Results showed a significant interaction between rat strain and cost requirements only during the negative incentive shift with the emotionally reactive Fischer 344 rats exhibiting significantly longer response latencies with increasing cost, highlighting greater negative contrast. These findings are more consistent with emotionality accounts of negative contrast and results of neurophysiological research that suggests shifting from a large to a small reward is aversive. Findings also highlight how subjective reward value and motivation is a product of gene-environment interactions

Maximizing The Value Of Your Small Business

This paper offers business owners a step-by-step valuation process for establishing the fair market value of their firms and stresses the importance of preparing for the due diligence process

A Test of the Aversive Transition Account: Extended Pausing Following Signaled Rich-Lean Transitions on Multiple Fixed-Ratio Schedules in Fischer 344 and Lewis Rats

On multiple schedules ending in two different magnitudes of reinforcement, a signaled transition from a preceding large (rich) to an upcoming small (lean) reinforcer occasions long post-reinforcer pauses compared to transitions from lean to rich, or when magnitude is constant (e.g., rich-rich and lean-lean transitions). A behavioral process that may underlie extended pausing at signaled rich-lean transitions is that these transitions are aversive and set the occasion for escape in the form of extended pausing. The present study evaluated this hypothesis by examining pausing at signaled rich-lean transitions in two inbred strains of rats putatively differing in sensitivity to aversive stimulation. Fischer 344 rats are more sensitive to aversive stimuli and so should pause longer than Lewis rats at the signaled transition from large to small reinforcers. Pausing was assessed at four different signaled transitions (rich-lean, rich-rich, lean-rich, and lean-lean) across a range of fixed-ratio values (1, 25, 50, 75, and 100). Consistent with the aversive transition hypothesis, Fischer 344 rats paused longer than Lewis rats at signaled rich-lean transitions at most ratio values. Control procedures suggest this difference is not due to motoric differences between rat strains