Pictorial target control of schedule-induced attack in White Carneaux pigeons.

The team placed hungry White Carneaux pigeons on a fixed-interval food schedule.

While the birds waited for grain, pictures of other pigeons were shown on a screen.

The researchers counted how often each bird pecked or struck the picture.

The pigeons attacked the pictures most when the image was an upright silhouette.

When food stopped, the attacks stopped too.

Pictures alone can trigger schedule-induced attack, not just real birds.

Dove (1976) later showed that hungrier birds attack a mirror more, linking body weight to strength of attack.

Uchino et al. (2014) used the same mirror set-up but trained birds to peck calmly, proving the response can be flipped from aggression to self-recognition.

Segal (1962) found that visual ‘clocks’ control timing, while Tracey et al. (1974) show visual targets control aggression—together they prove visual cues can steer very different pigeon behaviors under similar schedules.

You now know that pictures, not just live peers, can evoke attack during reinforcement gaps. If you run schedule-induced behavior studies, you can replace live targets with easy-to-change images, cutting animal welfare risks and giving tighter stimulus control. Try inserting a picture condition the next time you study adjunctive behavior.