Patterns of phoneme discrimination difficulty for adults with Down syndrome

Individuals with Down syndrome (DS) often experience disruption to speech and language processing. However, there is a paucity of research examining the specific characteristics of speech production and perception for this population. As a result, especially for adults with DS, very little is known about even fundamental characteristics of speech perception. Past research (Keller-Bell and Fox, 2007) has suggested that children with DS may have difficulty discriminating certain speech sounds. The current study examines discrimination of phoneme minimal pairs by adults with DS as it relates to hearing status and speech production. Adults with DS performed an AX discrimination task with stimuli differing on one, two, or three phonetic features and vowel minimal pairs. Accuracies in the AX task suggest that minimal pair discrimination varies by phonetic features as well as by participant. In particular, consonant place distinctions may be particularly difficult for individuals with DS but voicing and manner distinctions pose less difficulty. Vowel discrimination varies by participant with some having significant difficulty with vowel discrimination and others being at the ceiling. These results are considered in the context of speech production and hearing status.