Implicit causality bias in adults with traumatic brain injury

INTRODUCTION: Individuals with moderate or severe traumatic brain injury often experience impairments in pragmatic language functions. Pragmatic language has been studied primarily in connected language genres such as narratives. It may be, however, that individuals with traumatic brain injury also miss microscopic cues, such as social cues embedded in single word meanings or sentence structure. The current study examined one type of sentence-level pragmatic language cue: implicit causality bias. Implicit causality bias is the attribution of an interpersonal transitive verb action to either the subject noun phrase or object noun phrase of a sentence, and is an inherent property of English-language verbs. METHOD: In this study, 19 adults with traumatic brain injury and 18 typical adults were asked to provide sensible and spontaneous completions to 96 sentence fragments. Each fragment contained one interpersonal transitive verb and two noun phrases to which the cause of the verb could be attributed. RESULTS: Adults with traumatic brain injury showed significantly less implicit causality bias than typical adults, and also made more errors in assigning the causality of a clause. CONCLUSIONS: These results challenge assumptions regarding intact implicit processing in adults with traumatic brain injury, and reveal mechanisms by which communication could fail in everyday social interactions.