It is a problem if the sensory conditioning phenomenon depends upon the presentation of pair stimuli and the reinforcement which provides a mediating link or not. The present experiment was carried out to investigate how the color stimulus generalization gradients are produced by pigeons under differnt sensory controls and before or after the reward conditioning; in one case, a pigeon was put in the box illuminated by a mercury lamp which has relatively higher intensity at the range of long wavelength in spectral continuum, and in another case, by a neon lamp which has higher intensity at the range of short wavelength. In the reward couditioning before or after these sensory controls, a color light, 540 mM as the stimulus to be reinforced was presented through a monocrometer, and the bird was trained to peck at a light-on key. Following this training and sensory controls, the bird was tested with the previously reinforced color and the others, 645 mM, 585 mM, 495 mM, and 435 mM. The generalization gradients in successive six extinction trials appeard as follows ; in experimental groups the birds under control of the illumination by the mercury lamp built up relatively greater responses at the range of short wavelength than the one of long wave length and by the neon lamp vice versa. In control group under no sensory controls, pigeons did not produce the different responses between the ranges of wavelength at significant level. The result suggests that the presentation of pair stimuli and the reinforcement might be not necessary in sensory conditioning for the connection of stimuli which elicites the response.
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