Developmental changes in the effects of utterance length and complexity on speech movement variability.

Area of Science:

• Speech-language pathology
• Developmental neuroscience
• Linguistics

Background:

• Speech motor control involves complex coordination of articulators.
• Linguistic factors like utterance length and complexity influence speech production.
• Understanding developmental trajectories of speech motor skills is crucial.

Purpose of the Study:

• To investigate how utterance length and linguistic complexity affect speech movement consistency in children and adolescents.
• To analyze the developmental course of speech motor variability and its relation to linguistic constructs.
• To describe developmental trends in the duration of speech sequences within varying sentential contexts.

Main Methods:

• Recorded lower-lip movements in 210 participants aged 5-22 years.
• Analyzed movement variability and duration during the production of a target phrase in isolation and embedded sentences.
• Utilized variability and durational analyses to assess speech motor performance.

Main Results:

• Children showed higher speech movement variability compared to young adults across all conditions.
• Increased linguistic processing demands led to greater movement trajectory variability in most age groups.
• Adult-like phrase planning timing emerged around age 9, with continued maturation through adolescence.

Conclusions:

• Language and motor systems interact significantly throughout development.
• Speech motor development is a protracted process extending into adolescence.
• Linguistic complexity influences speech motor control across different developmental stages.