Two Rapid Odor Threshold Methods Compared to a Modified Method of Constant Stimuli

Sensory thresholds are defined according to a criterion level of performance in a particular psychophysical task. Thus, thresholds are a function of both subject sensitivity and method. However, relatively few studies have directly compared methods using the same subjects and stimulus. In the current work, thresholds for amyl acetate were measured for 19 subjects using three different methods. Results from a modified method of constant stimuli, which directly measures full detection functions, served as a gold standard to establish validity. These results were compared to two less intensive shortcut methods, viz., a forced-choice ascending method of limits and a staircase procedure. Both rapid methods produced mean threshold values comparable to those from the method of constant stimuli. Thus, both methods provided a reasonable estimate of average threshold. For characterizing individual differences, the validity of both methods seemed largely limited by their reliability. The staircase procedure may outperform the ascending method of limits in characterizing individual differences, but neither method is exceptionally strong in this respect.