Effects of alternative reinforcement on human behavior: the source does matter.
Free reinforcers help only if they touch the exact moment of the target response; otherwise they hurt.
01Research in Context
What this study did
The team gave college students a button-pressing task. While they worked, free points showed up on a screen.
The points came two ways. Sometimes they popped up right after a press. Other times they appeared on a fixed clock with no link to pressing.
The researchers watched what happened to the students’ steady pressing when these free goodies arrived.
What they found
Pressing stayed strong only when the free points landed at the same moment as a press.
When the points came on a separate timer, pressing dropped. The farther apart the point and the press, the bigger the drop.
How this fits with other research
Decasper et al. (1977) saw the same dip years earlier. They kept the response-reinforcer link but stretched the time gap. The 2003 study shows the dip still happens even when the link is gone.
Macht (1971) showed pigeons hang around longer where grain lasts longer. The new study adds the timing rule for humans: closeness beats size.
Charlop et al. (1985) shaped precise button rhythms in half an hour. Their fast shaping fits here—when free points land nearby, they can speed up, not slow down, the rhythm you already built.
Why it matters
If you sprinkle free reinforcers to keep motivation high, watch the clock. Deliver them right as the learner does the target move. A late prize can quietly weaken the very behavior you want to keep.
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02At a glance
03Original abstract
Competing theories regarding the effects of delivering periodic response-independent reinforcement (more accurately, response-independent points exchanged for money) on a baseline rate of behavior were evaluated in human subjects. Contiguity theory holds that these events decrease target responding because incompatible behavior is adventitiously strengthened when the point deliveries follow target behavior closely in time. Matching theory holds that response-independent points, like any other alternative reinforcer, should reduce target responding. On this view, temporal contiguity between target responding and response-independent point delivery is unimportant. In our experiment, four different responses (moving a joystick in four different directions) were reinforced with points exchangeable for money according to four independent variable-interval schedules. Different schedules of point delivery were then superimposed on these baselines. When all superimposed point deliveries occurred immediately after one of the four responses (the target response), time allocated to target responding increased. When the superimposed point deliveries could be delivered at any time, time allocated to target responding declined and other behavior increased. When superimposed points could never immediately follow target responses, time allocated to target responding decreased further and other behavior or pausing predominated. The findings underscore the contribution of temporal contiguity in the effects of response-independent deliveries of food, money, points, etc.
Journal of the experimental analysis of behavior, 2003 · doi:10.1901/jeab.2003.79-193