Persistent Neurobehavioral Markers of Developmental Morphosyntax Errors in Adults

Area of Science:

• Linguistics
• Developmental Psychology
• Neuroscience

Background:

• Children aged 2-4 years exhibit an optional infinitive stage in language acquisition, using nonfinite verbs where finite verbs are required.
• This stage, characterized by errors like omitted past tense -ed and third-person singular -s, typically resolves by age four but can persist in language impairments.
• It remains unclear if adults process these specific developmental errors differently from other grammatical mistakes.

Purpose of the Study:

• To investigate how adults process developmental optional infinitive errors compared to nondevelopmental errors and correct sentences.
• To examine the behavioral and neural correlates of processing these different types of grammatical errors in adults.

Main Methods:

• Adult participants (N=25) performed grammaticality judgments on sentences containing developmental optional infinitive errors, nondevelopmental agreement errors, and grammatically correct sentences.
• Behavioral data (accuracy, reaction time) and functional brain activation (fMRI) were recorded during auditory and visual presentation of sentences.

Main Results:

• Adults were significantly slower and less accurate when judging sentences with developmental optional infinitive errors compared to nondevelopmental errors and correct sentences.
• Sentences with developmental errors elicited greater activation in the bilateral inferior frontal gyri than sentences with nondevelopmental errors across both auditory and visual modalities.

Conclusions:

• The cognitive load associated with grammatical finiteness persists into adulthood, influencing sentence processing.
• The brain's engagement with developmental morphosyntactic errors suggests ongoing computational demands related to grammatical structure.
• These findings highlight the lasting impact of early language acquisition principles on adult grammatical processing and neural function.