The temporal organization of behavior on periodic food schedules.
Averaged response patterns can invent tidy waves that single-interval records never show—always plot raw data first.
01Research in Context
What this study did
McSweeney et al. (1993) watched rats on fixed-time food schedules. Every 60 s a pellet dropped no matter what the rat was doing.
The team recorded two things: how much the rat drank and how much it ran. They looked at each 60-s interval one by one. Then they averaged all intervals together.
They wanted to see if the average picture matched what really happened inside each interval.
What they found
Drinking and running did NOT take turns inside the interval. Both started right after the pellet.
The averaged graph looked like a neat two-part rhythm. The single-interval records showed the rhythm was fake.
The authors say the average created an illusion of shifting motivation that never happened.
How this fits with other research
Davis et al. (1994) saw the opposite. When they averaged fixed-interval data, the famous scallop appeared. Single records looked flat. Their average revealed a pattern; K’s average invented one.
Feldman et al. (1999) echo the warning. They studied fixed-ratio pauses and found averages hid skewed shapes. Both papers shout the same rule: look at the raw intervals before you trust the mean.
Roper (1978) and Anger et al. (1976) show that schedule length changes WHICH adjunctive behavior peaks. K’s work adds a caution: even if the behavior changes, averaging can still lie about WHEN it happens.
Why it matters
Before you tell a parent or teacher that a child’s problem behavior “peaks mid-interval,” open the single-session charts. If the average shows a tidy wave, check a few real intervals first. You might spare everyone a treatment plan aimed at a ghost.
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02At a glance
03Original abstract
Various theories of temporal control and schedule induction imply that periodic schedules temporally modulate an organism's motivational states within interreinforcement intervals. This speculation has been fueled by frequently observed multimodal activity distributions created by averaging across interreinforcement intervals. We tested this hypothesis by manipulating the cost associated with schedule-induced activities and the availability of other activities to determine the degree to which (a) the temporal distributions of activities within the interreinforcement interval are fixed or can be temporally displaced, (b) rats can reallocate activities across different interreinforcement intervals, and (c) noninduced activities can substitute for schedule-induced activities. Obtained multimodal activity distributions created by averaging across interreinforcement intervals were not representative of the transitions occurring within individual intervals, so the averaged multimodal distributions should not be assumed to represent changes in the subject's motivational states within the interval. Rather, the multimodal distributions often result from averaging across interreinforcement intervals in which only a single activity occurs. A direct influence of the periodic schedule on the motivational states implies that drinking and running should occur at different periods within the interval, but in three experiments the starting times of drinking and running within interreinforcement intervals were equal. Thus, the sequential pattern of drinking and running on periodic schedules does not result from temporal modulation of motivational states within interreinforcement intervals.
Journal of the experimental analysis of behavior, 1993 · doi:10.1901/jeab.1993.59-1