A cat jumping up from a nap and running to sit beside her food bowl when she hears the sound of the can-opener is a classic example of Pavlovian conditioning: the sound of the can-opener (conditioned stimulus) has been associated with food (unconditioned stimulus), and so prompts preparation for eating (conditioned response). But, if one then uses the can-opener to open all the cans needed to make a big pot of chili, the conditioned response may diminish because the conditioned stimulus (can-opener sound) and unconditioned stimulus (cat food) are no longer being reliably paired, and so the conditioned response is no longer being reinforced. This process is known as extinction.
In new research published in Journal of Experimental Psychology: Animal Learning and Cognition, Drew and colleagues (2017) examined how changing the duration of the conditioned stimulus after conditioning influences the rate of extinction.
Rats were trained to associate a 12-second auditory stimulus (conditioned stimulus) with the delivery of a food pellet (unconditioned stimulus) into a food compartment. In a subsequent extinction phase, the duration of the conditioned auditory stimulus was either the same as (12 seconds), shorter (6 seconds) or longer (24 seconds) than during training, and no food (unconditioned stimulus) was provided. The primary measure of interest was the rate of head entries into the food compartment (conditioned response).
The results showed that regardless of whether initial training followed a continuous (Experiment 1) or partial (Experiment 2) reinforcement schedule, increasing the duration of the conditioned stimulus led to faster extinction, but reducing the duration of the conditioned stimulus did not lead to slower extinction, relative to the original conditioning duration.
These results are inconsistent with the suggestion that extinction depends on cumulative conditioned stimulus exposure. However, faster extinction for longer durations may be an artifact of temporal rescaling in the 24-second group, as conditioned responses in this group were made later in the trial period. In other words, there were fewer responses in the 24-second group compared to the other groups when only the first 6 seconds of the conditioned stimulus period were analyzed, even on trials where a conditioned response was eventually made.
Such rescaling may reflect the fact that temporal expectations about conditioned-unconditioned stimulus relationships are relative with respect to conditioned stimulus duration, although shortening the conditioned stimulus duration (6-second group) did not have any effect on the timing of the conditioned response.
The authors interpret these results to suggest that extinction is a function of the number of conditioned stimulus presentations, not cumulative exposure to the conditioned stimulus, but changing the temporal characteristics of the conditioned stimulus can create the appearance of faster extinction due to temporal displacement of the response.
Citation
- Drew, M. R., Walsh, C., & Balsam, P. D. (2017). Rescaling of temporal expectations during extinction. Journal of Experimental Psychology: Animal Learning and Cognition, 43(1), 1–14. http://dx.doi.org/10.1037/xan0000127
Note: This article is in the Basic / Experimental Psychology topic area. View more articles in the Basic / Experimental Psychology topic area.