Bouts of responding from variable-interval reinforcement of lever pressing by rats.
Pay rate and a small added ratio pack more responses into tighter bouts, not just faster overall rates.
01Research in Context
What this study did
Katz et al. (2003) watched rats press a lever under a variable-interval schedule. They raised the payoff rate and then added a tiny VR4 requirement on top.
The team used log-survivor plots to split each rat’s session into bouts of rapid pressing and the quiet gaps between them.
What they found
More frequent pay and the extra VR4 made the rats start new bouts faster and stay in each bout longer.
Total lever presses climbed because both the starts and the within-bout speed increased.
How this fits with other research
Gabriels et al. (2001) ran the same rats and same method two years earlier and saw the same pattern—a direct replication.
Reed et al. (1988) and Reed (1991) swapped payoff size for payoff rate. Bigger pellets also raised VR response rates but could actually slow VI rates, showing schedule type matters.
Foltin (1997) and Pilowsky et al. (1998) looked like contradictions: longer access to wheel-running as a reinforcer cut lever pressing. The key difference is the reinforcer type—food boosts work, while extended running satiates the need to move.
Why it matters
When you shape client work, remember that both how often you pay and how you set the response requirement change the microstructure of behavior. If you want steady engagement, use richer pay or add a small ratio; if you use activity reinforcers, keep them short to avoid satiation. Track bout starts and lengths with simple inter-response-time checks to see whether your intervention is working on initiation or on speed inside the burst.
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02At a glance
03Original abstract
Four rats obtained food pellets by lever pressing. A variable-interval reinforcement schedule assigned reinforcers on average every 2 min during one block of 20 sessions and on average every 8 min during another block. Also, at each variable-interval duration, a block of sessions was conducted with a schedule that imposed a variable-ratio 4 response requirement after each variable interval (i.e., a tandem variable-time variable-ratio 4 schedule). The total rate of lever pressing increased as a function of the rate of reinforcement and as a result of imposing the variable-ratio requirement. Analysis of log survivor plots of interresponse times indicated that lever pressing occurred in bouts that were separated by pauses. Increasing the rate of reinforcement increased total response rate by increasing the rate of initiating bouts and, less reliably, by lengthening bouts. Imposing the variable-ratio component increased response rate mainly by lengthening bouts. This pattern of results is similar to that reported previously with key poking as the response. Also, response rates within bouts were relatively insensitive to either variable.
Journal of the experimental analysis of behavior, 2003 · doi:10.1901/jeab.2003.80-159