ANALYSIS OF POSITION OF TRIAL SEQUENCE AND TYPE OF DILUENT ON THE DETECTION THRESHOLD FOR PHENYL ETHYL-ALCOHOL USING A SINGLE STAIRCASE METHOD

Although detection thresholds for odors are commonly measured in acade mic and medical settings, the influences of procedural factors on thre shold values are poorly understood. The present study evaluated the in fluences of (i) trial sequence position and (ii) diluent type on the t hreshold value for the rose-like odorant phenyl ethyl alcohol. In Exp. 1, detection thresholds mere measured in 24 subjects on two occasions in which different diluents were used in the concentration series, pr opylene glycol and light mineral oil. The thresholds were estimated us ing a 7-reversal initially ascending single-staircase procedure. Thres hold values were significantly influenced by the type of diluent (lowe r for mineral oil) and trial sequence (lower for later threshold rever sals). In Exp. 2, 24 subjects were administered a staircase threshold lest which continued through 15 staircase reversals. Continued testing resulted in a significant lowering of the threshold measure. These fi ndings demonstrate the importance of both diluent and test length on d etection threshold values measured by a single staircase procedure and emphasize the need for standardization of procedures for threshold te sting.