Some effects of d-amphetamine on the behavior of pigeons under intermittent reinforcement

The effects of d-amphetamine (0.25 to 8.0 mg/kg) were studied on key-pecking behavior under variable interval (high response rate) and DRL reinforcement (low response rate) in pigeons. Doses of 2.0 mg/kg and above progressively decreased VI responding, as was the case for DRL with doses 4.0 mg/kg and above. No consistent increases in response output on either reinforcement schedule were observed with any dose of the drug, even though prior studies have suggested that amphetamine ought to increase DRL behavior. When their behavior was reduced by d-amphetamine, DRL birds often earned many more grain reinforcements than usual, but frequently did not consume them. No effects of d-amphetamine were observed on a color discrimination tested in the VI birds.