Selected abstracts from the Journal of the Experimental Analysis of Behavior, November 1994.
Immediate conditioned stimuli can make uncertain rewards more appealing than sure ones, but only if the delay stays razor-short.
01Research in Context
What this study did
Researchers let pigeons pick between two keys. One key always gave food. The other key gave food only half the time.
The birds chose in two steps. First they pecked to enter a 'link.' Then they waited for the food or no-food result. Sometimes the wait was short, sometimes long. Sometimes a short gap of silence came before the result.
What they found
When the wait was short, the pigeons preferred the 50% key. The bright key light itself acted like a treat, even though it only signaled maybe-food.
When the wait grew or a gap was added, the birds flipped. They now liked the sure-thing key. The value of the light faded once it was delayed.
How this fits with other research
Martin et al. (1997) ran the same 50% vs 100% setup and added a 5-second gap. They saw the same flip: the gap killed the birds' love for the risky key. This is a clean lab replication.
Green et al. (1987) had earlier shown that birds usually pick the surer side. The 1995 study does not overturn that; it just shows that a flashy stimulus can briefly override the math when delays are tiny.
Mazur et al. (1992) mixed things up by making the link lengths hop around. They also found that extra lights could push choice around, backing the idea that conditioned reinforcers steer the ship.
Why it matters
For your clients, the takeaway is timing. A token, praise, or brief light works only if it arrives right after the target response. Insert even a small pause—like walking to the treasure box—and the conditioned reinforcer loses punch. Deliver it fast or bridge it with an immediate signal to keep reinforcement strong.
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02At a glance
03Original abstract
Pigeons' choices between a reliable alternative that always provided food after a delay (i.e., 100% reinforcement) and an unreliable one that provided food or blackout equally often after a delay (i.e., 50% reinforcement) was studied using a discrete-trials concurrent-chains procedure modified to prevent choice between alternatives following a blackout outcome. Initial links were fixed-ratio 1 schedules, and terminal links were fixed-time schedules. Stimuli presented during the terminal-link delays were correlated with the food and blackout outcomes. In Experiment 1, terminal-link durations were varied. With short terminal links (i.e., 10 s), 6 of 8 subjects showed strong preference for the 50% side. As terminal-link duration increased to 30 s, preference, regardless of direction, became less extreme. In Experiment 2, the side-key location of the 50% and 100% alternatives was reversed for 3 subjects. Preference for the 50% alternative reoccurred following the key reversal. When a 5-s separation was subsequently interposed between the initial and terminal links for both alternatives, all birds reversed to a preference for the 100% side. In general, the strong preference for the 50% side was qualitatively consistent with the expectation that the procedure enhanced the conditioned-reinforcement effectiveness of the food-associated terminal-link stimulus on the 50% side. Implications of the results for various accounts of choice of the 50% alternative are discussed.
Journal of applied behavior analysis, 1995 · doi:10.1901/jaba.1995.28-387