Adult and Child manifolds were generated by synthesizing 5 X 5 matrices of/Cej/ type utterances in which F2 and F3 frequencies were systematically varied. Manifold stimuli were presented to 11 graduate-level speech-language pathology students in two conditions: (a) a rating condition in which stimuli were rated on a 4-point scale between good /r/and good /w/; and (b) a labeling condition in which stimuli were labeled as "R," "W," "distorted R." or "N" (for none of the previous choices). It was found that (a) stimuli with low F2 and high F3 frequencies were rated 1.0nmdas;1.4; those with high F2 and low F3 frequencies were rated 3.6–4.0, and those with intermediate values were rated 1.5–3.5; (b) stimuli rated 1.0–1.4 were labeled as "W" and stimuli rated 3.6–4.0 were labeled as "R"; (c) none of the Child manifold stimuli were labeled as distorted "R" and one of the Adult manifold stimuli approached a level of identification that approached the percentage of identification for "R" and "W": and (d) rating and labeling tasks were performed with a high degree of reliability.
