Effects of chlordiazepoxide and cocaine on concurrent food and avoidance-of-timeout schedules.
Cocaine slows both food and timeout-avoidance responding when the two run together, but speeds timeout-only avoidance when food is absent.
01Research in Context
What this study did
Scientists gave rats two jobs at once. Press one lever to earn food. Press another lever to avoid a short timeout. The rats worked under both schedules at the same time.
The team then injected cocaine or chlordiazepoxide. They watched how each drug changed the rats’ work rate on both levers.
What they found
Cocaine lowered pressing on both levers. Higher doses meant fewer presses for food and fewer presses to avoid timeout.
Chlordiazepoxide was trickier. Small doses sped up pressing. Large doses slowed it down. The pattern differed from older shock-avoidance studies.
How this fits with other research
Davison et al. (1995) ran a near-copy study the next year. They also used cocaine and timeout avoidance, but removed the food lever. In that setup, cocaine raised timeout responding instead of lowering it. The difference shows that food in the mix flips cocaine’s effect.
Davison et al. (1991) had already shown that morphine cuts timeout pressing while sparing shock avoidance. Together, the three papers prove that drug impact depends on the kind of aversive event being avoided—timeout versus shock.
Byrd (1980) found that cocaine can either speed or slow key pressing depending on the schedule type. The 1994 data now extend that rule to concurrent schedules with timeout.
Why it matters
If you study or treat behavior under negative reinforcement, remember that timeout and shock are not equal. A drug or intervention that calms shock-avoidance might wreck timeout-avoidance, and vice versa. Always state the aversive event clearly in your protocols and pilot any new medication with both food and avoidance components in view.
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02At a glance
03Original abstract
Five rats were trained on a concurrent schedule in which responses on one lever produced a food pellet on a random-interval 30-s schedule during 10 s of food availability associated with distinctive exteroceptive stimuli. Responses on another lever postponed for 20 s the presentation of a 50-s timeout, during which all stimuli were extinguished and the schedule contingencies on the food lever were suspended. The response rates maintained by the random-interval schedule exceeded those maintained by the avoidance contingency, but both provided a stable baseline to assess the behavioral effects of different drugs. Low doses of cocaine hydrochloride (1 and 3 mg/kg) did not affect food-reinforced responding or avoidance response rates. Intermediate doses (5.6, 10, and 13 mg/kg) produced a dose-dependent decrease in food-maintained and avoidance response rates, and both types of responding were virtually eliminated after administration of the highest doses (17 and 30 mg/kg) of cocaine. Low doses of chlordiazepoxide (1 and 3 mg/kg) increased food-maintained and avoidance response rates, and both rates decreased systematically after 10 and 30 mg/kg of this drug. The effects of cocaine and chlordiazepoxide on response rates maintained by avoidance of timeout from food presentation were unlike those reported when subjects responded to avoid shock presentation. The results of this experiment thus provide evidence to suggest that the effects of drug administration on avoidance behavior may be a function of the nature of the consequent event to be avoided.
Journal of the experimental analysis of behavior, 1994 · doi:10.1901/jeab.1994.61-479