Good sensory measurements require that we look at the tasters as measuring instruments
that are somewhat variable over time and among themselves, and are very prone to bias.
To minimize variability and bias, the experimenter must understand the basic physiologi-
cal and psychological factors that may inﬂuence sensory perception. Gregson (1963) notes
that perception of the real world is not a passive process, but an active and selective one.
An observer records only those elements of a complex situation that he can readily see and
associate as meaningful. The rest he eliminates, even if it is staring him in the face. The
observer must be put in a frame of mind to understand the characteristics that he or she is
to measure. This is done through training (see Chapter 9), and by avoiding a number of
pitfalls (Amerine, Pangborn, and Roessler 1965; Pangborn 1979; Poste et al. 1991; Lawless
and Heymann 1998) inherent in the presentation of samples, the text of the questionnaire,
and the handling of the participants.