|Habituation to the Reinforcer and Within-Session Changes in Responding
|Monday, May 26, 2008
|9:00 AM–10:20 AM
|Area: EAB; Domain: Basic Research
|Chair: Eric S. Murphy (University of Alaska, Anchorage)
|Discussant: Frances K. McSweeney (Washington State University)
|Abstract: Three studies tested the hypothesis that habituation, a decrease in responsiveness to repeatedly-presented stimuli, occurs during operant conditioning procedures. Aoyama examined the effects of post-session wheel running on within-session decreases in food-reinforced responding in rats. He discovered that within-session decreases in responding were steeper when subjects were given post-session access to the running wheel. Scott-Weber, Lupfer-Johnson, and Murphy studied within-session changes in responding when dwarf hamsters served as subjects. They reported that within-session decreases in responding were steeper at higher, than at lower, rates of food reinforcement. Scott-Weber et al.’s findings are inconsistent with satiation as an explanation because the dwarf hamsters did not consume the food reinforcers. Instead, the food pellets were stored in their cheek pouches. Kenzer, Fuller, and Ghezzi linked basic research on habituation and dishabituation to research involving humans. They reported that changes in the reinforcer type, amount, and selected properties of the antecedent stimuli were related to dishabituation of operant responding in humans. The results of these three studies support the idea that habituation accrues to reinforcing stimuli in three different species.
|Effects of Activity-Based Anorexia Procedure on Within-Session Changes in Nose-Poke Responding.
|KENJIRO AOYAMA (Doshisha University)
|Abstract: This study tested the effects of activity-based anorexia (ABA) procedure on within-session changes in responding. In the ABA group (N=8), rats were given a 60-min feeding session and allowed to run in a running wheel the remainder of each day. During a daily 60-min feeding session, each nose-poke response was reinforced by a food pellet. In the control group (N=8), rats experienced the same procedure except that the wheel was locked and thus rats could not run. The experiment lasted for 6 days. Rats in the ABA group consumed less and lost more body weight than those in the control group. Within-session decreases in nose-poke responding were steeper for ABA than control rats. In addition, response rates were well described as linear functions of the cumulative number of reinforcements in both groups (R2s>.93). The regression lines for the ABA group had steeper slopes and smaller x-axis intercepts than those for the control group. However, the y-axis intercepts of the regression lines for both groups were similar. These effects were different from the effects of taste-aversion learning induced by post-session wheel running (Aoyama, 2007), suggesting different mechanisms in both preparations.
|Within-Session Changes in Responding of Dwarf Hamsters (Phodopus campbelli).
|MICHELLE SCOTT-WEBER (University of Alaska, Anchorage), Gwen Lupfer-Johnson (University of Alaska, Anchorage), Eric S. Murphy (University of Alaska, Anchorage)
|Abstract: Four dwarf hamsters responded on variable-interval schedules that provided programmed rates of food reinforcement ranging from 60 to 480 reinforcers per hour. Rate of responding increased, decreased, or increased and then decreased within the sessions. The within-session pattern of responding changed with changes in the programmed rate of reinforcement. Within-session decreases in responding were steeper during the richer schedules than during leaner schedules. These findings are inconsistent with satiation because the dwarf hamsters stored most of the food reinforcers in their cheek pouches. Instead, these results are consistent with the idea that sensitization and habituation to the sensory properties of the reinforcer contribute to within-session changes in operant responding (e.g., McSweeney & Roll, 1998).
|More on Dishabituation of Operant Responding.
|AMY KENZER (Center for Autism and Related Disorders, Inc.), Timothy C. Fuller (University of Nevada, Reno), Patrick M. Ghezzi (University of Nevada, Reno)
|Abstract: Increasingly, the scientific evidence suggests that habituation does occur within the operant conditioning paradigm. As such, recent evidence is available which indicates that dishabituation of an habituated operant response may occur following changes in the schedule of reinforcement, reinforcer magnitude, and extraneous stimuli (Aoyama & McSweeney, 2001; McSweeney & Roll, 1998; Murphy et al., 2003; Murphy, 2003). This study was designed to link basic research on habituation and dishabituation to research involving humans. Thus changes in the reinforcer type, amount, and selected properties of the antecedent stimuli were evaluated to determine the effects on dishabituation of operant responding in humans.