Comparison of speech-language pathologists' and naive subjects' identification of synthesized /r-w/ continua

Two 9-step continua varying in F2 and F3 frequencies between exemplary /r/ and /w/ were synthesized to represent child and adult talkers. Stimuli from the full and truncated versions of the continua were presented to naive subjects in Experiment 1 and to speech-language pathologists in Experiment 2. Shifts from full range continua category boundaries occurred in Experiment 1 for both truncated "R" and truncated "W" conditions and in a direction opposite to the truncated end of the continuum. The results of Experiment 2 indicated that the full-range category boundaries for speech-language pathologists differed from those for naive subjects but that the boundary shift for truncated "R" was as great as that for naive subjects and the boundary shift for truncated "W" was greater than that for naive subjects. These findings indicate that speech-language pathologists are more likely than naive individuals to judge ambiguous /r/ sounds as "W" and that the phonetic judgments of speech-language pathologists about /r/ sounds are no more stable than those of naive subjects.