Auditory stimulus control in pigeons: Jenkins and Harrison (1960) revisited.

The team worked with pigeons in a sound chamber.

Some birds heard only tones. Others heard tones plus a small key light.

After training, all birds were tested with many tones to see how sharply they pecked only to the trained pitch.

Pigeons trained without the key light showed a steep drop-off. They pecked mostly to the trained tone and little to nearby pitches.

Birds that saw the light while hearing the tone spread their pecks across more pitches. The visual cue had stolen control from the sound.

Nelson et al. (1978) later used the same lab style with college students. Hearing a word once made the students say it moments later. Both studies show that a single prior sound can push later behavior.

Castañe et al. (1993) found that seeing a color briefly made students later "guess" that color when asked about past events. Like the pigeons, human verbal answers were nudged by a small visual cue.

St Peter (2017) argues that these shifts are not magic. They happen because extra sights or sounds create collateral responses that overshadow the target stimulus. The pigeon data give that theory clean animal proof.

When a client misses an auditory discrimination, scan the room for lights, toys, or your own face. These extras can overshadow the sound you want to control. Run a quick probe with the visual cue removed. If responding sharpens, you have found the culprit and can fade or delay the cue.