Odours are evaluated in relation to a target by testing a subject by presenting the subject with one or more odours under different conditions, at least some being in the presence of one or more targets; monitoring brain activity, preferably electrical activity of the subject; and evaluating the monitored brain activity in relation to odour/target combinations presented to the subject. Evaluation of brain activity for odour/target combinations presented to the subject provides a measure of the degree of association between the odour and target in a particular odour/target combinations. These measures can be compared and used as a basis of odour selection. <IMAGE>
