Safety signals reinforce instrumental avoidance in humans.
A quick safety signal right after an avoidance act can strengthen that act, even when the aversive event is already gone.
01Research in Context
What this study did
CTGreenlee et al. (2024) ran five small lab tests with neurotypical adults.
Each person could press a key to avoid a mild buzz. A short tone sometimes played right after the press.
The team asked: does the tone itself make people avoid more, even when the buzz is already gone?
What they found
People pressed the key more often when the tone followed the press.
The tone acted like a tiny reward. It strengthened the avoidance habit on its own.
The buzz never changed; only the safety signal did the extra work.
How this fits with other research
Alba et al. (1972) saw the same thing in rats decades ago. Rats only kept smooth, timed patterns when a light flashed after each bar press. Without the light, the pattern fell apart.
THOMAS et al. (1963) showed that humans learn free-operant avoidance best alone, not in pairs. CTL’s 2024 study adds the next layer: once a person is working alone, a brief safety sound can still push the rate higher.
Together, the three papers trace one clear line: signals that mark "safe now" are reinforcers, not just cues.
Why it matters
If you run desensitization or avoidance programs, pair the escape response with a clear, immediate safety signal. A short beep, a green card, or a thumbs-up can do part of the reinforcing work for you. You might then thin other rewards faster without losing the behavior.
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02At a glance
03Original abstract
Safety signals reinforce instrumental avoidance behavior in nonhuman animals. However, there are no conclusive demonstrations of this phenomenon in humans. Using human participants in an avoidance task, Experiments 1-3 and 5 were conducted online to assess the reinforcing properties of safety signals, and Experiment 4 was conducted in the laboratory. Participants were trained with CSs+ and CSs-, and they could avoid an aversive outcome during presentations of the CSs+ by pressing their space bar at a specific time. If successful, the aversive outcome was not presented but instead a safety signal was. Participants were then tested-whilst on extinction-with two new ambiguous test CSs. If participants made an avoidance response, one of the test CSs produced the trained safety signal and the other was a control. In Experiments 1 and 4, the control was followed by no signal. In Experiment 2, the control was followed by a signal that differed in one dimension (color) with the trained safety signal, and in Experiment 3, the control differed in two dimensions (shape and color) from the trained safety signal. Experiment 5 tested the reinforcing properties of the safety signal using a choice procedure and a new response during test. We observed that participants made more avoidance responses to the ambiguous test CSs when followed by the trained signal in Experiments 1, 3, 4, and 5 (but not in Experiment 2). Overall, these results suggest that trained safety signals can reinforce avoidance behavior in humans.
, 2024 · doi:10.1101/lm.053914.123