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Levels of risk assessment evoked by either a synthetic predator odor or noncontact exposure to live rats were examined under white or red light conditions. Defensive responses to the predator odor were infrequent in white light and showed a modest, but reliable, increase under red light. Noncontact exposure to rats, in contrast, produced considerably higher levels of risk assessment than did odors in white light, and these levels were nearly doubled under red light. Judicious selection of eliciting and background stimuli may provide considerable control over the intensity of risk assessment. Such procedures may prove useful for the study of anxiety-like states.