The stimuli consisted of three confusable pairs of different
low concentration NaCl solutions: 7 and 10 mM, 10 and
13 mM, and 12 and 15 mM. The stimulus pair to be discriminated
was not fixed. It was varied randomly over the three
pairs, in order to have judges focus only on the differences
between the stimuli in the pair and to minimize any learning
effects. For convenience, the stimulus with lower concentration
in each stimulus pair will be denoted as ‘W’ (as the
weaker stimulus) and the stimulus with higher concentration
will be denoted as ‘S’ (stronger stimulus).