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 .
C1521970
characteristics
C1444754
length