Effects of signaling on temporal control of behavior in response‐initiated fixed intervals

Fox and colleagues asked a simple question. What happens if you flash a bright light right when the first response starts a fixed-interval clock?

They used pigeons in a response-initiated fixed-interval schedule. The bird’s first peep started a timer. After the set time, the next peck paid off.

Sometimes the first peck also turned on a white light. Other times it did not. The team watched how fast the birds pecked and how well they timed the interval.

The signal sped up the first response. Birds pecked sooner after the last food delivery when the light came on.

But the same signal made later timing sloppier. Spread-out responding and more early pecks showed the birds were less sure when food was due.

In short, the cue helped the start and hurt the finish of the interval.

Robertson et al. (2013) set the baseline. They showed that simply adding a response-initiation requirement already raises early pecking and makes intervals more variable. Fox’s team kept that setup and layered on the signal, proving the cue—not just the initiation rule—drives the extra speed.

Arnett (1972) seems to disagree. That study found any added clock cue cuts response rate and stretches the post-food pause. Fox saw faster, not slower, responding. The gap is real but explainable: B’s cue stayed on for every response, acting like a tiny delay, while Fox’s cue flashed only once, acting like a green light.

Wolchik et al. (1982) add a twist. They showed that signaling even a half-second delay can trim rapid, off-time responses. Fox’s signal did the opposite at the start, but it also loosened later precision, echoing the same theme: salient cues rearrange when responses occur.

If you run FI schedules with clients, remember that a single bright event at the start works like a starter’s pistol. It can cut the post-reinforcement pause but may scatter responding across the rest of the interval. Use the signal when you want quick initiation, then watch for drift. Fade or add extra cues later if steady timing matters for the skill you are teaching.