Variable-interval escape from stimuli accompanied by shocks.
Conditioned warning stimuli keep VI escape responding alive even when shocks are scarce.
01Research in Context
What this study did
Rats pressed a bar to escape mild shocks that arrived on a variable-interval schedule.
Sometimes the shock came with a red light and buzzer that had been paired with shock earlier.
The study compared bar-pressing when the warning stimuli were present versus when they were not.
What they found
Bar-pressing stayed strong when the warning stimuli were on.
Without the warning stimuli, pressing slowed as the time between shocks grew longer.
The red light and buzzer kept escape behavior alive even when shocks became rare.
How this fits with other research
Schroeder et al. (1969) later showed the same pattern in adult humans. People slowed their button pressing when shocks punished the responses, and the VI schedule made the drop gradual, just like the rats’ escape rates.
McKearney (1970) seemed to flip the story: punishment suppressed VI responding faster than ratio schedules. The key difference is contingency. In DINSMOOR (1962) the warning stimuli signaled upcoming shock, so pressing removed both stimuli and shock—double reinforcement. In W the shock punished pressing, so the same stimuli became extra cost.
WEINER (1964) conceptually replicates the magnitude effect. When point losses grew larger, human subjects switched from escape to quicker avoidance, mirroring how the conditioned stimuli in DINSMOOR (1962) kept escape brisk even at low shock rates.
Why it matters
Warning stimuli can make or break an escape program. If you want a safety response to stay strong when danger is rare, pair early warning cues with the threat and let the response cancel both. Check that your cues are truly conditioned aversive stimuli, not neutral prompts, or you may see the same fade that happened in the control condition.
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02At a glance
03Original abstract
Individual performances of three rats were examined under a procedure in which steady rates of bar pressing were maintained by conditioned aversive stimulation. Originally neutral visual and auditory stimuli were accompanied by widely and irregularly spaced pulses of shock; they were terminated on a variable-interval schedule by pressing a bar. The contingencies between behavior and shock were also duplicated in a control procedure in which no visual or auditory stimuli were provided. Pressing observed under the control procedure was attributed to differences in the aversiveness of pressing and nonpressing behavior engendered by differences in the incidence of shock following the two classes of behavior. Increased rates with visual and auditory stimuli were attributed to termination of conditioned aversive stimulation. Control rates declined more rapidly than did experimental rates as the mean interval between successive shocks was lengthened; both rates tended to decline when less than 60 sec was allowed as time out from shocks following the successful response. In the control procedure, discrimination between the continuation and discontinuation of the shock series, as measured by relative rates, depended on the relative length of the interval between shocks and the time-out period. Regular warm-up accelerations in rate were noted following an initial delay in responding at the beginning of each session. The length of time required for the warm-up depended on the length of the mean interval between shocks, indicating that exposure to a certain amount of shock was required to establish a supporting state for the observed performance.
Journal of the experimental analysis of behavior, 1962 · doi:10.1901/jeab.1962.5-41