Auditory discrimination: a three-variable analysis of intensity effects.

Cherek et al. (1970) worked with rats in a small lab chamber. The rats pressed levers for food pellets.

The team tested three sound features: how loud the tones were, how much louder one tone was than the other, and the overall volume range. They wanted to see which features helped the rats tell the tones apart.

Each sound feature changed the rats' lever pressing in a clear, orderly way. Bigger differences between tones made learning faster.

The three features also worked together. A small change in one feature could be fixed by changing another. This gives teachers more ways to build clear cues.

KIEFFETHOMAS (1965) showed that even a 'neutral' buzzer can gain control over rat behavior. Cherek et al. (1970) moved one step further by proving that the exact intensity of that buzzer matters just as much as its presence.

Fahmie et al. (2013) later found that when reward odds shift, rats first change their bias, then slowly sharpen accuracy. The 1970 data help explain why: intensity sets the stage, but reward rules fine-tune the response.

Meltzer (1983) swapped sound for light and rats for pigeons, yet found the same lesson: keep reward rates steady or you will measure bias, not true skill. Together these papers form a toolkit for spotting artifacts in any discrimination task.

When a client struggles to tell two spoken words apart, check three knobs: how loud each word is, how much louder one is than the other, and the overall volume range. A small tweak on any knob can speed learning without extra trials. If you also hold reward rates constant, you will know the change came from clearer cues, not from guessing.