Combining stimuli signalling response-dependent food and shock.

Pigeons pecked a key for food on some days and to avoid shock on others. A light alone, a tone alone, or both together told the birds which schedule was active.

The team compared response rates when each stimulus stood alone versus when the light and tone played together.

The light-plus-tone pair pushed the highest peck rates in both the food and the shock phases. Response rate jumped even when shock risk rose.

Two stimuli acting as one cue beat any single stimulus, no matter the consequence.

Thomas et al. (1968) saw the opposite: when they paired two reinforcer cues, birds responded at a middle rate, not higher. The key gap is shock. R’s birds faced only food schedules; A’s birds faced food and shock. Mixed consequences may let stimulus combination win.

Podlesnik et al. (2017) later extended the combo idea to extinction. They mixed an ‘alternative’ stimulus with the target cue and cut responding further. Together the papers show that extra stimuli can strengthen control in both reinforcement and extinction.

Van Hemel (1973) showed a single cue works best when it perfectly predicts payoff. Lattal (1974) adds that stacking two perfect predictors can give even more control.

If you want sharper stimulus control, try pairing cues—light with sound, color with shape—instead of swapping them. This may boost correct responses even when task difficulty or mild punishment rises. Test the combo in your next teaching or reduction program and track if rates climb.