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Comparisons between variable-interval and fixed-interval schedules of electric shock delivery
Journal of the Experimental Analysis of Behavior
|January 1, 1973
Summary
Fixed-interval shock schedules suppress responding more than variable-interval schedules in rats. However, a preceding cue significantly reduced this suppression, altering the impact of shock predictability on behavior.
Area of Science:
- Behavioral neuroscience
- Animal behavior
- Learning and conditioning
Background:
- Understanding how predictable versus unpredictable aversive events influence behavior is crucial for behavioral science.
- Previous research indicates that the schedule of reinforcement and punishment significantly impacts operant responding.
Purpose of the Study:
- To investigate the differential effects of fixed-interval (FI) versus variable-interval (VI) shock schedules on ongoing operant behavior in rats.
- To examine the role of a conditioned stimulus (CS) in modulating the suppressive effects of shock delivery.
- To explore how the probability of CS-shock pairings influences response suppression under different shock schedules.
Main Methods:
- Rats were trained on a variable-interval (VI) 35-sec food reinforcement schedule.
- Response suppression was measured under different schedules of shock delivery: 60-sec and 240-sec FI and VI.
- Experiments involved presenting a visual stimulus (CS) preceding shock delivery at varying probabilities (0%, 50%, 100%).
Main Results:
- FI shock schedules produced greater response suppression than VI shock schedules.
- A 5-sec visual stimulus preceding shock significantly reduced overall response suppression for both FI and VI schedules.
- Under FI shock, response suppression was highest with 0% cue presentations and lowest with 100% cue presentations.
- Under VI shock, response suppression was highest with 50% cue presentations, lowest with 100%, and intermediate with 0%.
Conclusions:
- The predictability of shock delivery, particularly under fixed-interval schedules, plays a significant role in behavioral suppression.
- Conditioned stimuli can attenuate the aversive impact of shock, suggesting a role for classical conditioning in modulating operant behavior.
- The interaction between shock predictability and cue presence highlights the complexity of aversive control in animal learning.