Influences of repeated testing on nonesterified fatty acid taste.

Findings that support the ability of humans to taste nonesterified fatty acids have been qualified by claims of substantial individual variability in sensitivity. We tested whether the number of testing visits impacted detection thresholds. Additionally, we explored the possibility that methodological differences in reported studies contributed to the high level of variance. Participants were randomized to either the modified staircase or ascending 3-alternative forced-choice methods, completed 10 test visits, and then switched to the alternate method. Repeated testing lowered the threshold concentration, and regardless of starting method, threshold concentrations were significantly lower with the second method. The staircase method generated data with less variation. The ascending method appears to be able to distinguish hypo and hypersensitive individuals as the variance at each visit increased over time, suggesting that the top performers continued to improve while the hyposensitive subjects maintained their low level of performance. The best individual threshold performance (lowest stimulus concentration) at each visit was obtained with the ascending method for 7 out of the first 10 visits (P = 0.117) and 17 out of the 20 visits (P = 0.001). Despite potential advantages of the ascending method in terms of sensitivity separation, there was no difference between the median of the first 10 visits, second 10 visits, and overall median obtained by the 2 testing methods. The most appropriate detection threshold testing method will depend on the goals of the researcher.