Changes in blood pressure and heart rate during fixed-interval responding in squirrel monkeys.
Heart rate mirrors the scalloped response curve on fixed-interval schedules in monkeys.
01Research in Context
What this study did
DeWeese (2009) watched squirrel monkeys work on a fixed-interval schedule. Every few minutes they could avoid a mild shock by pressing a lever.
The team tracked heart rate and blood pressure while the monkeys worked. They wanted to see if heart activity matched the speed of lever pressing.
What they found
Heart rate and blood pressure rose when the monkeys pressed faster. Both dropped when the monkeys took a break.
The heart tracked the work pattern second by second, not just at the end of the session.
How this fits with other research
Kelleher et al. (1969) used a similar shock set-up and also saw the scalloped response pattern. Both labs show that squirrel monkeys make the same curved rate pattern under threat of shock.
Arnett (1972) added clock lights to pigeons on fixed-interval. The lights slowed the birds down. Jo’s monkeys had no added lights, so their heart rate could follow the natural speed-up and slow-down.
Ley (2001) showed that past training history stops mattering after many sessions. Jo’s monkeys had long stable histories, so their heart signals reflect the current schedule, not old rules.
Why it matters
You can treat heart rate as a real-time measure of work effort on fixed-interval schedules. If you track a client’s pulse during DRO or DRL sessions, spikes may tell you when motivation is rising even before the client responds. Try adding a cheap fitness watch next time you run a timing-based intervention and watch the curve appear on your data sheet.
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02At a glance
03Original abstract
Episodic and sustained increases in heart rate and mean arterial blood pressure can occur with recurring patterns of schedule-controlled behavior. Most previous studies were conducted under fixed-ratio schedules, which maintained a consistent high rate of responding that alternated with periods of no responding during times when the schedule was not in operation. The present study examined changes in heart rate and blood pressure under fixed-interval schedules which maintained a range of rates that varied from little or no responding at the beginning of the fixed interval to high rates at the end of the interval. The relations of cardiovascular function to rate of responding were examined. Squirrel monkeys prepared with arterial catheters were trained to respond under fixed-interval schedules of electric-shock presentation. The duration of the interval was varied across sessions and cardiovascular parameters were examined. Local rates of responding were typically near zero during timeout periods, low at the beginning of each fixed-interval cycle, and then increased as the fixed interval progressed. At most schedule durations, arterial blood pressure and heart rate levels were lowest at the beginning of the interval cycles, increased as the rate of responding increased, and then decreased during the timeout periods. At all parameters studied, there was a direct relationship between changes in response rate within fixed-interval cycles and changes in heart rate and blood pressure. The results suggest that a much closer concordance of these cardiovascular parameters and schedule-controlled responding is obtained by examining ongoing behavior as it occurs within the contingencies by which it is maintained.
Journal of the experimental analysis of behavior, 2009 · doi:10.1901/jeab.2009.92-379