Abstract
Pigeons were trained to peck a key in the presence of a 1000-Hz tone on a variable-interval one-minute schedule of reinforcement. One group was trained with an illuminated key; the other was trained in a totally dark chamber. During a generalization test on tonal frequency, subjects trained and tested with the key illuminated produced rather shallow gradients around the training value; subjects trained and tested in the dark produced steeper generalization gradients. These data replicate Jenkins and Harrison's (1960) finding that tone acquires relatively little control over responding and demonstrate that this absence of control is a function of the presence of the keylight.