Abstract
Previous research has demonstrated that rats will increase their rates of lever pressing for sucrose rewards in the first half of an experimental session when food pellets, rather than the same sucrose, continually serve as the reward in the second half of the session. This effect has been coined induction, and the present study investigated whether it could be altered by altering "motivational" variables. Experiment 1 manipulated subjects' motivation by altering, across conditions, their level of food deprivation. Predictably, the size of induction varied directly with level of deprivation. Experiments 2 and 3 manipulated subjects' motivation by feeding them food pellets and sucrose, respectively, prior to their responding in the experimental session. These pre-session feedings decreased the size of the observed induction in both experiments. The results from the present study indicate that the size of induction is correlated with subjects' motivation to respond for the available reinforcers. They are also consistent with the idea that operant processes underlie the effect. The notion that induction might encompass the concept of "anticipation" is also discussed.
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Notes
Finding changes in response rates within sessions during the 1%–1% conditions can be considered normal, if not expected, given the body of research on within-session changes in operant responding (e.g., McSweeney and Roll 1993). As can be seen in Fig. 1, the changes in response rates during the 1%–1% were small and took the form of either an increase followed by a decrease in responding, or simply a decrease in responding across the session. Such results are consistent with previous research that has studied rats lever pressing for low-concentration sucrose reinforcers (Melville et al. 1997; experiment 2).
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Acknowledgements
The authors thank Grant Bauste, Brent King, Kelsey Lang, and Janel Palbicki for their help in collecting the data. The also thank F. Richard Ferraro for his comments on an earlier version of this manuscript. Portions of this research were funded by an award to JNW from North Dakota EPSCoR, a subprogram of NSF.
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Weatherly, J.N., Arthur, E.I.L. & Tischart, L.M. Altering "motivational" variables alters induction produced by upcoming food-pellet reinforcement. Anim Cogn 6, 17–26 (2003). https://doi.org/10.1007/s10071-003-0160-4
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DOI: https://doi.org/10.1007/s10071-003-0160-4