The comprehension of sentences with unaccusative verbs in aphasia: a test of the intervener hypothesis.
Natalie Sullivan, Matthew Walenski, Tracy Love and 1 others
PMID 27909354WHAT IT FOUND
People with agrammatic Broca's aphasia understood simple sentences with unaccusative verbs well, but failed to understand the same verbs when they appeared inside subject relative clauses.
This suggests that an intervening noun phrase blocks their ability to link the verb to its object.
Key findings
01Participants with agrammatic Broca's aphasia showed above-chance comprehension of complement phrase sentences (91% accuracy) but chance-level comprehension of subject relative clause sentences (46% accuracy).
02The significant difference in performance between the two sentence types in the aphasia group was not seen in the age-matched control group, who performed well on both.
03The authors argue that the presence of an intervening noun phrase in the relative clause disrupts the processing of the dependency chain, leading to comprehension failure.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study included only seven participants with aphasia, which limits the generalisability of the findings to the wider population. The task was a controlled laboratory experiment using sentence-picture matching, which may not fully reflect real-world conversational comprehension. The study focused on non-alternating unaccusative verbs, so results may not apply to other verb types or sentence structures.
The easy way to misread this
Do not interpret the poor performance on relative clauses as evidence that agrammatic Broca's aphasia causes a general deficit in understanding unaccusative verbs. The deficit was specific to the relative clause structure containing an intervening noun; comprehension of the same verbs in simpler complement phrases was intact.