STIMULUS CONTROL OF THE PIGEON'S ABILITY TO PECK A MOVING TARGET

Two pigeons were trained to peck whichever of eight keys displayed a white field (S D ). The other seven keys displayed a white “X” on a black background (S Δ ). Each peck to S D produced three‐second access to grain, a three‐second intertrial interval (ITI), and the next trial. Pecks to S Δ produced a three‐second timeout (TO) and the same trial. During later sessions the key displaying S D changed every t seconds ( t =3, 2, 1, .5, and .25 sec), requiring the birds to track the position of the S D . Pecks on a ninth key increased t . Several sessions employed novel stimuli to ascertain the controlling stimulus dimensions. Both birds made few errors acquiring the original discrimination. During the tracking sessions, both birds made few errors when t =.5 sec. Only one reliably lengthened t . Data from sessions with novel stimuli indicate that color and form were important aspects of S D and S Δ respectively; movement contributed to the final performance.