Are acronyms really irregular? : preserved acronym reading in a case of semantic dementia

This paper describes the progressive performance of JD, a patient with semantic dementia, on acronym categorisation, recognition and reading aloud over a period of 18 months. Most acronyms have orthographic and phonological configurations that are different from English words (BBC, DVD, HIV). While some acronyms, the majority, are regularly pronounced letter by letter, others are pronounced in a more holistic, and irregular, way (NASA, AWOL). Semantic dementia at its moderate stage shows deficits in irregular word reading while reading accuracy for regular words and novel words is preserved. Nothing is known about acronym comprehension and reading ability in semantic dementia. Thus, in this study we explore for the first time the impact that semantic decline has on acronym recognition and reading processes. The decline in JD's semantic system led to increasingly impaired semantic categorisation and lexical decision for acronyms relative to healthy controls. However, her accuracy for reading aloud regular acronyms (i.e. those pronounced letter by letter such as BBC) remained near ceiling while reading irregular acronyms (i.e. those pronounced as mainstream words such as NASA) demonstrated impairment. It is therefore argued that consequences of semantic impairment vary across acronym types, a finding that informs our understanding of any reading account of this growing class of words.