A comparison of responding maintained under second-order schedules of intramuscular cocaine injection or food presentation in squirrel monkeys.
Schedule structure, not reinforcer type, controls response patterns in second-order schedules.
01Research in Context
What this study did
Wetherington (1979) worked with squirrel monkeys under second-order schedules.
The team compared two reinforcers: intramuscular cocaine and regular food.
They wanted to see if the drug, not the schedule, shaped the animals’ response patterns.
What they found
The schedule structure ruled the behavior, not the reinforcer.
Monkeys produced the same burst-and-pause pattern whether they worked for cocaine or for food.
Cocaine did not create a special “drug” pattern; the contingencies did.
How this fits with other research
Morse et al. (1966) saw the same thing 13 years earlier with shock termination.
Their monkeys also followed the schedule, proving the rule holds for both good and bad consequences.
Terrace (1969) looks like a contradiction: ICS sharpened stimulus discrimination more than food.
The gap is in the procedure. S used multiple schedules that highlight stimulus differences, while L used second-order schedules that highlight temporal rules.
Sievert et al. (1988) later added random-interval baselines and still found cocaine mirroring food, tightening the replication net.
Why it matters
If you run token boards, chained schedules, or any second-order system, focus on the timing rules.
The prize—candy, praise, or break—won’t override the pattern the schedule creates.
Check your program structure first before blaming the reinforcer when behavior looks odd.
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02At a glance
03Original abstract
Key pressing by squirrel monkeys was maintained under second-order schedules of either intramuscular cocaine injection or food presentation. Under one schedule, each completion of a 10-response fixed-ratio unit produced a brief visual stimulus; the first fixed-ratio unit completed after 30 minutes elapsed produced the stimulus paired with either cocaine injection or food presentation. Generally, short pauses followed by high rates of responding were maintained within the fixed-ratio units, and responding was positively accelerated over the 30-minute interval. Under another schedule, each completion of a 3-minute fixed-interval unit produced the brief stimulus; completion of the 10th fixed-interval unit produced the stimulus paired with either cocaine injection or food presentation. Generally, short pauses followed by high rates of responding were maintained within the fixed-ratio units, and responding was positively accelerated over the 30-minute interval. Under another schedule, each completion of a 3-minute fixed-interval unit produced the brief stimulus; completion of the 10th fixed-interval unit produced the stimulus paired with either cocaine injection or food presentation. Rates of responding increased within the fixed-interval units, and to a greater extent over the entire 10 fixed-interval units. Patterns of responding depended more on the schedule of reinforcement than on whether cocaine or food maintained responding. Omitting the brief stimuli following all but the last fixed-ratio or fixed-interval units decreased average rates and altered the patterns of responding. Substituting a visual stimulus that was never paired with cocaine or food following all but the last fixed-ratio or fixed-interval units decreased response rates to a lesser extent and did not substantially alter patterns of responding. When the duration of the paired stimulus was varied from .3 to 30.0 seconds, the highest response rates occurred at intermediate durations (1.0 to 10.0 seconds). The manner in which the stimulus changes affected performances depended more on the schedule of reinforcement than on whether cocaine injection or food presentation maintained responding.
Journal of the experimental analysis of behavior, 1979 · doi:10.1901/jeab.1979.32-419