Effects of shifts in food reinforcement context on rats’ consumption of concurrently available water or sucrose solution

Rich-lean transitions produced by stimuli associated with accurate and inaccurate responding by pigeons

Discriminable transitions from relatively favorable schedules of reinforcement to unfavorable schedules (rich-lean transitions) can produce disruptions in operant behavior. A prior evaluation in our laboratory (Toegel et al., 2021) found that placing a border around a key displayed on a resistive touchscreen increased pigeons' response accuracy relative to conditions without the border. We sought to evaluate (a) whether effects of the key border on accuracy could be replicated in a within-session comparison and (b) whether transitions from a response alternative associated with accurate responding to one associated with inaccurate responding functioned as rich-lean transitions. Pigeons' key pecks were reinforced according to a two-component multiple schedule with identical fixed-ratio (FR) requirements and reinforcer magnitudes. The components differed based on whether the virtual key was displayed behind a border or with no border. In line with prior research, within-session comparisons yielded higher response accuracy in components with the key border than in components without the border. Furthermore, transitions from the border component to the no border component functioned as rich-lean transitions for pigeons whose obtained FRs in no border components were substantially larger than the FR programmed in that component.

Effects of chlordiazepoxide on pausing during rich-to-lean transitions

Extended pausing during discriminable transitions from rich-to-lean conditions can be viewed as escape (i.e., rich-to-lean transitions function aversively). Thus, an anxiolytic drug would be predicted to mitigate the aversiveness and decrease pausing. In the current experiment, pigeons' key pecking was maintained by a multiple fixed-ratio fixed-ratio schedule of rich (i.e., larger) or lean (i.e., smaller) reinforcers. Intermediate doses (3.0-10.0 mg/kg) of chlordiazepoxide differentially decreased median pauses during rich-to-lean transitions. Relatively small decreases in pauses occurred during lean-to-lean and rich-to-rich transitions. Effects of chlordiazepoxide on pausing occurred without appreciable effects on run rates. These findings suggest that signaled rich-to-lean transitions function aversively.