Interresponse time duration in fixed-interval schedules of reinforcement: control by ordinal position and time since reinforcement.

Schwarz et al. (1970) watched pigeons peck a key under a fixed-interval schedule.

They recorded every interresponse time and noted its place after food.

The goal was to see when timing settles down inside the interval.

After the sixth peck, the pauses between pecks stopped changing.

Earlier pecks sped up if many responses had already happened.

Time since the last food also made early pecks faster.

Davison (1969) saw a dip-peak pattern right before food under fixed-ratio, but L et al. found steady timing after peck six under fixed-interval. The schedules create different micro-rhythms.

Johnston et al. (1972) went a step further and actually reinforced a 1-2 second pause, proving the pause itself is an operant. L et al. described the pattern; M et al. showed you can shape it.

Mahoney et al. (1971) stretched the interval so it changed every cycle. Their birds still used the post-reinforcement pause as a timer, backing up L et al.’s claim that pause length carries timing information.

When you run fixed-interval probes, start your data window after the sixth response. Early pecks are still wobbly and can skew your count. If you want steady responding, wait for the timing to lock in.