Improving odour detection by assessors

In a test of theoretical predictions made by MacRae and Falahee (1995), tra ined 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 being odour-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 bet ween odorous and odour-free samples was not really enhanced since 'false al arms' increased correspondingly. Incorporating additional, different odours into the sequence of samples and giving knowledge of results when these we re judged, dramatically improved performance - the rates both of missing tr ichloroanisole and of mistakenly attributing odour to odour-free samples we re halved. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ . All rights reserved.