Probabilistic models for sequential taste effects in triadic choice.

Sequential effects and positional response bias are accounted for in new models for triadic choice. These models were applied to data on distilled water and dilute NaCl solutions by use of the triangular and 3-alternative forced-choice methods with 4 participants. The concept of a "conditional stimulus" is introduced to describe stimuli that are created partially by prior oral environmental effects. The effects of 1 or 2 prior stimuli on triadic choice was evaluated. The triad models used were based on a Thurstonian variant of M. W. Richardson's (1938) method of triads and a Thurstonian model for first choice among 3 possibly different stimuli. Maximum likelihood estimates of the scale values for conditional stimuli and bias parameters showed that it was necessary only to consider 1 prior stimulus. It was also shown that salt concentration differences are not the physical analog of the mental representations for the conditional stimuli. The results strongly suggest a water taste to salt taste continuum.