Abstract
The odor of 2-heptanone was delivered by a precision olfactometer to five Ss using five methods of single-sample presentation of concentrations: (1) randomized, (2) sequential-down, (3) sequential-up, (4) constant stimulus—10 samples, and (5) constant stimulus—100 samples. Lowest thresholds were obtained with method (3) and the highest threshold resulted from method (2). Large variations in individual sensitivities between Ss were observed, precluding averaging of data in the constant stimulus methods. The latter were not suitable for measuring thresholds. No decrease in sensitivity due to fatigue or adaptation was noted in the 100-sample presentation; however, significant differences were found between the statistical errors of the first and second kind. When two odorous samples were presented concurrently within a series, a larger number of correct responses were obtained than when an air blank preceded the presentation of the odor, suggesting physical and/or psychological carry-over of stimulus. Specific modifications of the constant-stimulus method are discussed.
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