Effects of fixed-time shocks and brief stimuli on food-maintained behavior of rats.
A stimulus that marks ‘safe’ time can keep behavior going after the aversive event stops.
01Research in Context
What this study did
Wilkie et al. (1981) worked with lab rats pressing a lever for food pellets.
The team first gave shocks on a fixed-time schedule while a short tone played.
Later they kept the tone but removed every shock to see if the sound alone would keep the food pattern alive.
What they found
The tone that once said ‘safe period’ kept the lever-pressing pattern strong even with no more shocks.
The sound had turned into a conditioned reinforcer through its pairing with shock-free time.
How this fits with other research
Hearst et al. (1970) saw the opposite: their pre-shock tone shut avoidance down and the rats got more shocks.
The difference is timing. E’s signal meant ‘shock soon,’ so the rats froze. M’s signal meant ‘shock can’t happen now,’ so the rats kept working.
Lewis et al. (1976) and Liberman et al. (1973) already showed rats prefer signalled shock when the cue is a dependable safety signal. M extends this line by proving the safety cue alone can maintain behavior after shocks end.
Why it matters
You can build safety signals in therapy to protect skill gains when aversive events fade.
Pair a brief song, word, or light with periods free of demands or noise.
Later, present the cue alone to keep cooperation high even when the stressor is gone.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Pick a 5-second tune you play only when demands are off; later play it during work breaks to keep engagement up.
02At a glance
03Original abstract
When a fixed-time schedule of shocks was presented to rats lever pressing for food on a random-interval schedule, a pattern of behavior developed with a high rate of pressing after shock declining to near zero before the next shock was delivered. Once this pattern had stabilized, one-quarter of the shocks were replaced with brief auditory stimuli (tones) in a random sequence. Tone maintained behavior similar to shock, although tone was never paired with shock. Both tone and shocks elicited responding when presented at various times as probe stimuli, and responding was usually totally suppressed if neither stimulus occurred at the beginning of the fixed-time interval. When other stimuli were paired with tone and shock, only those paired with tone gained discriminative control and elicited responding. These findings suggest that stimuli that signal a shock-free, or safe, period will maintain the pattern of behavior generated by shock on a fixed-time schedule. There is a parallel between this phenomenon and the control of behavior on second-order schedules of positive reinforcement with nonpaired brief stimuli.
Journal of the experimental analysis of behavior, 1981 · doi:10.1901/jeab.1981.36-353