Fig. 3.
Discrimination. Associative performance indices (PIs) are presented for the discrimination task, in which animals were trained and tested differentially with any one of the odour elements (X) versus a mixture containing it (XY). The larger the perceptual distance between element and mixture, the easier should discrimination be and thus the more conditioned behaviour one should observe (i.e. the higher the PI scores should be). Thus, in this task perceptual distance can be approximated by the dDIS scores. A Kruskal–Wallis test (P<0.05, N=12 in all cases) reveals that depending on the odours used, perceived distance differs between elements and mixture. See Fig. 1 legend for odour definitions.