Choosing Schedules of Signaled Appetitive Events Over Schedules of Unsignaled Ones

Abstract

Two experiments were completed allowing albino rats to choose between signaled and unsignaled reward conditions. These experiments examined the effects on preference of (1) response dependent versus response-independent reward and, (2) food pellets versus chocolate milk as the reward. All subjects preferred the signaled condition over the unsignaled condition, whether exposed to response-dependent, or to response-independent delivery of rewards. Preference was controlled most effectively by presenting both the signal itself and the correlated stimulus identifying the signaled condition. The signal presented alone (Extinction 3) controlled preference more effectively than did the stimulus correlated with the signaled condition (Extinction 2). The second experiment showed that the quality of the reinforcer (pellets and chocolate milk) did not affect preference for signaled reward since all subjects preferred the signaled condition at levels comparable to those observed in Experiment 1, with food pellets. These results, along with others, argue against species differences, response-dependency, and reinforcer quality as variables affecting the direction of preference.

Factors Affecting Choice of Signaled or Unsignaled Food Schedules

“…No prefood signal was available during the unsignaled schedule. Three subjects were tested using a commitment procedure (see below) identical to that used in Badia et al (1981) with the exception that the response initiating the changeover condition was a shuttle response and not a lever-press response. Two additional subjects were tested using a noncommitment procedure similar to Experiment 1.…”

“…These results indicate that the discrepant findings of earlier studies are due to procedural differences involving signal duration and choice commitment. The data are consistent with a conditioned reinforcement interpretation of choice.Key words: choice, signaling, food, shuttle response, ratsSeveral investigators have reported that subjects prefer signaled food schedules over unsignaled ones (e.g., Badia, Ryan, & Harsh, 1981;Lewis, Lewin, Muehleisen, & Stoyak, 1974;Ryan & Badia, 1982). Lewis et al (1974), for example, found that pigeons acquired a keypeck changeover response that converted an unsignaled variable-interval food schedule to a signaled one for 1-min periods.…”

“…Additionally, Wilkie (1973) and Marcucella and Margolius (1978) reported that their subjects (pigeons), at times, spent more time on an unsignaled food schedule than on a signaled one in a concurrent-schedules choice test. Unfortunately, the studies yielding different outcomes involve different apparatus and procedures, making it difficult to determine reasons for the conflicting findings.The study by Badia et al (1981) addressed the differences in the findings of Lewis et al (1974) and of Hershiser and Trapold (1971). Subjects were first given forced exposure to signaled and unsignaled food schedules in an operant chamber and then were tested by giving them the opportunity to change, for brief periods of time, from the unsignaled to the signaled schedule (during some test sessions) or vice versa (during other test sessions).…”

“…The study by Badia et al (1981) addressed the differences in the findings of Lewis et al (1974) and of Hershiser and Trapold (1971). Subjects were first given forced exposure to signaled and unsignaled food schedules in an operant chamber and then were tested by giving them the opportunity to change, for brief periods of time, from the unsignaled to the signaled schedule (during some test sessions) or vice versa (during other test sessions).…”

“…Several investigators have reported that subjects prefer signaled food schedules over unsignaled ones (e.g., Badia, Ryan, & Harsh, 1981;Lewis, Lewin, Muehleisen, & Stoyak, 1974;Ryan & Badia, 1982). Lewis et al (1974), for example, found that pigeons acquired a keypeck changeover response that converted an unsignaled variable-interval food schedule to a signaled one for 1-min periods.…”