A Hierarchical Approach to Efficient Assessment of Functional Intelligibility: The Modular FITI (Functional Importance to Intelligibility) Phrase List

Abstract

Purpose: Gurevich and Kim (2023a) developed speech stimuli with full phonetic coverage and phonemic balance to comprehensively examine production and perception of consonants. They identify a hierarchy of positional variants with functional importance to intelligibility (FITI). The FITI stimuli are well suited for assessing intelligibility. Multiple studies report that clinicians prefer nonstandard materials (e.g., reading passages, word lists) over formal tools (e.g., Frenchay Dysarthria Assessment–Second Edition [FDA-2]; Enderby & Palmer, 2008), citing time constraints among reasons. Having analyzed the phonetic coverage of the three standard passages (Gurevich & Kim, 2022), the purpose herein is to provide a similar analysis for the FDA-2 and to construct an alternative list of stimuli that achieves strategic coverage of priority intelligibility targets and is adaptable to time constraints. Method: The FDA-2 word list was analyzed in terms of its coverage of the 466 allowable contexts for the 24 English consonants and its coverage of priority FITI targets. A subset of the stimuli from Gurevich and Kim (2023a) was used to construct phrases organized in modules from highest to lowest FITI priority. Results: The full FDA-2 word list covers 35.41% of the allowable 466 contexts, compared to 83.05% by the 308 FITI word list from Gurevich and Kim (2023a). It also underperforms in covering priority FITI targets but does capture some of the hierarchy if all 115 words are used. Fifteen modules were constructed from the 308 FITI words with one to five phrases per module, presented in order of highest to lowest FITI priority. Conclusions: The newly constructed list of phrases has comprehensive phonetic coverage, follows the FITI hierarchy, and is built in autonomous modules. Using the modular FITI phrases to investigate speech is adaptable to time constraints in a manner that prioritizes intelligibility targets.