Rats’ Response Rates for 1 % Sucrose When Food-Pellet Reinforcement is Upcoming: Effect Of Upcoming Reinforcement Contingency

Abstract

Previous research has demonstrated that rats' rates of lever pressing for 1 % liquid-sucrose reinforcers in the first half of a 50-min session increase when food-pellet, rather than the same sucrose, reinforcement will be delivered in the second half of the session. The present study investigated whether this increase (i.e., induction) would be influenced by alterations to the responsereinforcer relationship in the second half of the session. Experiment 1 manipulated this relationship by delaying reinforcers in the second half of the session by 0.1, 1.0, or 10.0 s, in different conditions. Induction was little affected by the delays. Experiment 2 provided reinforcers in the second half of the session on a different schedule of reinforcement (fixed ratio, fixed interval, or differential reinforcement of low rates) across conditions. Induction was large when the fixed-ratio schedule was upcoming and small or absent when the differential-reinforcement-of-Iow-rates schedule was upcoming. These differences, however, covaried with differences in obtained reinforcement. Experiment 3 eliminated the response-reinforcer relationship in the second half of the session by, in some conditions, delivering reinforcers on a variable-time schedule. Doing so reduced the size of, but did not eliminate, the observed induction. The present results increase the generality of induction and suggest that both the type of upcoming reinforcer and the contingency that will deliver that reinforcer can contribute to its appearance.A series of recent studies have reported that rats' rates of lever pressing for low-concentration (i.e., 1 or 5%) liquid-sucrose reinforcement are increased when food-pellet, rather than the same sucrose, reinforcement will be available later in the same session (Weatherly,

Induction When Rats Respond for Liquid-Sucrose Reinforcement as a Function of Amount of Upcoming “Work”

“…On their face, the present results would seem inconsistent with those of Weatherly, Moulton, et al (2002), who found that the size of induction was reduced when the upcoming food pellets would be delivered independent of responding. Yet the results may not necessarily be at odds.…”

Effects of Haloperidol on Responding Maintained with Food and Sucrose-Water

“…For Group W-F, increasing the rate of foodpellet presentation in the second VI component produced a concomitant increase in lever pressing maintained by sucrose-water presentation, even though the rate of sucrose-water presentation was held constant in the first VI component. These data resembled those documented in several studies (e.g., Weatherly et al, 1999;Weatherly & Moulton, 2001;, and may qualify as induction because receiving food pellets in the second VI schedule, rather than sucrose water, might represent an improvement in the upcoming conditions of reinforcement (Weatherly et al, , 2002. Interestingly, however, we found the same result for Group F-W; lever pressing maintained by food pellets increased in the first VI component by increasing the rate of sucrose-water presentation in the second VI component.…”

“…In these studies of lever pressing maintained by 1 or 5 % of sucrose solution increased in the first VI if food-pellets, rather than the same sucrose solution, were delivered in the second VI. The interpretation of this result is that food-pellets delivered in the second half of the session represented an increase in the reinforcer value relative to either 1 or 5 % liquid-sucrose obtained in the first half of the session Stout, Davis & Melville, 2001;Weatherly, Stout, Rue & Melville, 2000, Weatherly, Moulton & Ritt, 2002Weatherly, Arthur & Tischar, 2003).…”

On the determinants of induction in responding for sucrose when food pellet reinforcement is upcoming

“…Previous studies Weatherly, Himle, et al, 2001;Weatherly et al, 2002;Weatherly, Stout, et al, 2000) have reported that response rates for sucrose increased when food pellet, rather than the same sucrose, reinforcement was available in the second half of the session. However, it is also possible that continued sucrose reinforcement actually decreases response rates.…”

“…For example, subjects may increase their response rate for sucrose when food pellet reinforcement is upcoming, because they are readying themselves to respond at a high rate for the food pellets. However, Weatherly, Moulton, and Ritt (2002) found that upcoming food pellets increased operant response rates for 1% sucrose even when the pellets would be delivered independently of responding.…”