Schedule-induced aggression as a function of fixed-ratio value.

Cherek et al. (1970) tested pigeons on fixed-ratio food schedules. They raised the ratio, then lowered it, and watched for pecking at another bird.

Aggression rose when the ratio got bigger and fell when it got smaller. The peak came days after the change.

Bigger fixed ratios made the birds attack more. The effect was slow, not instant.

When the ratio dropped again, fighting faded over several days.

Nelson et al. (1978) saw the same pattern with water. Longer food intervals doubled rat drinking. The form differed—aggression vs. polydipsia—but both grew as food grew farther apart.

O'Leary et al. (1979) moved the effect to humans. Token schedules made adults pace the room. It shows schedule-induced behavior crosses species and topographies.

Bachman et al. (1988) followed the same pigeons further. After many ratio hikes the birds cooled their bodies at night to save energy. Aggression is the first link; physiology adjusts later.

When you thin a reinforcement schedule, watch for side effects. A client may not hit you, but extra mouthing, pacing, or water-seeking can bloom days later. Ease the ratio back down and give the behavior time to drop before you judge the change a failure.