Re: identification task...negative d' values.

[John Culling <CullingJ@xxxxxxxxxxxxx>]

Negative d's that occur consistently can be meaningful in that:- 

1) the absolute value gives the discriminability of pairs of stimuli
2) the sign indicates the ordering of the stimuli along the perceptual 
    dimension  that the listeners were instructed to use for their decisions.

However, for the task described, which does not employ a single
perceptual dimension, it does imply that the labels used by the 
participants simply did not conform to those the experimenter
expected when designing the data collation.

Presumably there are more than 3 stimuli in the described continuum.
How has the experimenter decided where the phoneme boundaries
between one vowel label and the next "should" be?

John.