Composite control of pecking by keylight stimuli

Additive summation, typically demonstrated after training rats to bar press in tone alone and light alone, and cease pressing in the absence of tone and light, consists of more responding to a compound of separately conditioned stimuli (e.g. tone and light) than to its elements. Pigeons, responding to tone and light compounds, and rats, responding to a flicker frequency and brightness compounds projected from a bulb encased within in a translucent response lever, have also demonstrated additive summation. In Experiment 1, pecking was brought under the control of hue and brightness stimuli localized on the response key. In Experiment 2, keylight hue and shape controlled responding. None of the six pigeons tested produced additive summation. Stimulus functions were either not preserved in combinations or not separately established.