Improving odour detection by assessors

In a test of theoretical predictions made by MacRae and Falahee (1995), trained assessors evaluated water samples which sometimes contained 10^-5 mg/l of trichloroanisole, using three different procedures. Compared with the blue-book method of single-sample assessment, providing a reference sample identified to the assessor as beingodour-free increased the proportion of responses reporting an odour.This decreased the number of odorous samples missed. Although this outcome may be valuable in itself, discrimination between odorous and odour-free samples was not really enhanced since `false alarms' increased correspondingly. Incorporating additional, different odours intothe sequence of samples and giving knowledge of results when these were judged, dramatically improved performance - the rates both of missing trichloroanisole and of mistakenly attributing odour to odour-free samples were halved. [ABSTRACT FROM AUTHOR]