Acoustic phenotypes for speech-genetics studies: reference data for residual backslash 3 backslash distortions

An eventual genetic account of at least one subtype of child speech disorde rs may require the use of acoustic markers to phenotype children and family members. Acoustic markers have the potential for sensitivity and specifici ty that are not available using auditory-perceptual procedures such as phon etic transcription. Prior reports on the use of acoustics in speech-genetic s research have described methods to complete large-scale acoustic analyses , addressed relevant technical and linguistic sampling issues, and provided an acoustic reference database for /s/ production in adolescents. The pres ent paper addresses additional methodological issues and demonstrates how r eference data might be used for speech-genetics studies of another class of frequently persisting speech errors-distortions of the English rhotics /r/ and 3(iota)/. Findings support the need to adjust acoustic reference data by age and gender, and to subgroup reference data by rhotic phoneme and pho netic context. We describe a z score procedure that accommodates these meth odological needs. A companion paper uses these data to develop an acoustic phenotype marker of residual /3(iota)/ distortions for speech-genetics rese arch.