UC San Diego

Two experiments explored the difference in common chemical sensitivity between smokers and nonsmokers. The first experiment confirmed and extended our previous finding that smokers have a higher threshold than nonsmokers for a short-latency, reflex transitory apnea in response to a nasal irritant (carbon dioxide). The experiment revealed that even short periods of smoking (6-10 min) just before the measurement will further impair the smoker's sensitivity to an irritant. Application of the novel scaling technique magnitude matching, whereby persons judged the perceived magnitude of various levels of an irritant, odorant, and tone in the same session, implied that smokers actually perceive irritation less keenly than nonsmokers. The psychophysical functions for pungency in the two groups suggested that the insensitivity may arise from conductive factors (e.g., thickening of the mucus barrier) rather than from neural factors. The results of the scaling and those for the threshold for transitory apnea showed excellent quantitative agreement and indicated that the threshold for the reflex occurred at a criterion level of perceived pungency.