Eccentric stimuli on multiple fixed-interval schedules.

Whitehead et al. (1975) worked with pigeons on a fixed-interval food schedule. They slipped in one oddball flash or tone at an unexpected spot in each cycle. The team watched how this single 'eccentric' stimulus changed key-peck speed across three small experiments.

Every time the oddball cue popped up, the birds pecked faster right away. The jump was large and reliable, even though the cue had no link to food or punishment. The authors call the jump a 'disinhibition' effect — the surprise stimulus briefly lifted the normal pause seen early in an FI schedule.

Reed (2003) also added an extra signal inside FI schedules, but saw mixed results. The difference: Phil's signal arrived right after a peck and helped only if the bird was already pecking fast. E's eccentric cue came at an unrelated moment and helped every bird no matter its prior speed.

Blough (1971) fits the story better. M showed that a stimulus predicting free grain also speeds key-pecking. Both studies prove that neutral or 'bonus' cues can raise response rate through Pavlovian-instrumental overlap, not just through true reinforcement.

Harris et al. (1978) looks like a mirror image. They gave rats d-amphetamine and saw rate go up or down depending on past training. E's cue gives an instant, one-way boost, while C's drug effect is history-bound. Together they warn: know whether your rate change comes from an immediate stimulus or from past contingencies.

If you run FI or DRL sessions, any sudden noise, light, or movement can act as an eccentric stimulus and inflate response rate. Check your room for flickering bulbs, chatty staff, or hallway bells. These 'neutral' events may look like progress, but they could fade once the novelty wears off. Track when boosts happen and remove or control the accidental cue to be sure your intervention is really driving the change.