Development and maintenance of attack in pigeons during variable-interval reinforcement of key pecking.
Long VI schedules invite post-reinforcement aggression—shorten the interval or split the reinforcer to protect your session.
01Research in Context
What this study did
Dove et al. (1974) worked with pigeons on variable-interval schedules. They wanted to see when attack behavior shows up.
The birds pecked a key for food. The team slowly stretched the time between reinforcers. They watched for any aggression toward a target bird.
What they found
Attack started once the VI schedule reached about 90 seconds. It peaked when the interval hit 300–600 seconds.
Most attacks came right after food delivery. The longer the wait, the more the birds fought. Key pecking dropped as fighting rose.
How this fits with other research
Duker et al. (1996) later showed that bigger food portions also raise attack under fixed-interval schedules. Together the papers tell us both “how long” and “how much” matter for adjunctive aggression.
Friedling et al. (1979) used fixed-time food that ignored the birds’ responses. Attack still appeared, proving the inter-food interval is the key driver, not the peck itself.
Bhaumik et al. (2008) held the food rate constant and compared response-dependent FR with response-independent VT. Attack was stronger when the bird had to work. This extends the 1974 finding by showing that the response requirement itself adds fuel to the fire.
Why it matters
If you run thick VI or FR schedules with long gaps, watch for problem behavior right after reinforcement. The same “post-reinforcement pause” that helps us measure schedules can also trigger aggression. Try shorter intervals, smaller bites, or added tasks to break up the wait and keep clients calm.
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02At a glance
03Original abstract
Key-peck responses of two pigeons were maintained on variable-interval schedules of food reinforcement in the presence of a stuffed pigeon to study the characteristics of attack induced by that schedule. The mean interval of the schedule was increased from 15 sec to 600 sec in eight steps before an intermediate interval was reintroduced. The principal characteristics of attack were: (1) substantial attack first occurred on a variable-interval schedule of 90 sec in one pigeon and at 180 sec in the other, (2) the highest attack rates occurred on variable-interval schedules of 300 sec and 600 sec, (3) attack rate generally increased to a maximum and then decreased to a lower level across sessions at each schedule, (4) attacks developed a postreinforcement locus across the initial sessions on all schedules and, except on variable-interval schedules of 300 and 600 sec, occurred primarily in the postreinforcement period during extended training, (5) attack rates and key-peck rates were not recovered when the intermediate-length schedules were reintroduced, and (6) attack rate and key-peck rates were negatively correlated. Except for the fact that the maximum attack rates occurred at interfood intervals of 300 and 600 sec, and that attack and key-peck rates were negatively correlated, these findings have counter-parts in experiments with other reinforcement schedules.
Journal of the experimental analysis of behavior, 1974 · doi:10.1901/jeab.1974.21-563