Background. This paper reviews the role of deliberative processes in language-those language processes that require central resources, in contrast to the automatic processes of lexicalisation, word retrieval, and parsing. Aims. We describe types of deliberative processing, and show how these processes underpin high-level processes that feature strongly in language. We focus on metalinguistic processing, strategic processing, inhibition, and planning. We relate them to frontal-lobe function and the development of the fronto-striate loop. We then focus on the role of deliberative processes in normal and pathological development and ageing and show how these processes are particularly susceptible to deterioration with age. In particular, many of the commonly observed language impairments encountered in ageing result from a decline in deliberative processing skills rather than in automatic language processes. Outcomes & Results. We argue that central processing plays a larger and more important role in language processing and acquisition than is often credited. Conclusions. Deliberative language processes permeate language use across the lifespan. They are particularly prone to age-related loss. We conclude by discussing implications for therapy.

Background. At what point does "not telling" become "not knowing"? Previous research shows that Alzheimer's disease (AD) affects people's ability to define words, primarily, it has been thought, because AD destroys the semantic representations of words that the patients can no longer define. We investigate an alternative hypothesis, which is the idea that AD affects metalinguistic ability, which in turn affects people's ability to produce good definitions. Aims. Does AD affect metalinguistic abilities? Are definitions poor because people lose semantic information, or because they lose the knowledge of what constitutes a good definition? Methods & Procedures. We first established what constitutes good definitions of a set of words denoting animate and inanimate concepts. We then asked elderly people with AD to define these words. As expected, their definitions were very poor. However, we then asked them forced and open-choice questions about the information that they omitted from their definitions. Outcomes & Results. We show that people with AD can access semantic information that they appear to have lost. The AD group performed significantly worse than control participants on a word definition task, but importantly, some of the information they did not provide spontaneously was offered after questioning Conclusions. We conclude that although our participants with AD have lost some semantic knowledge, on at least some occasions they do not provide information that they do still know because of a metalinguistic impairment. In particular, the participants with AD no longer understand what constitutes a good definition. We argue this metalinguistic impairment results in part from frontal atrophy. Our results have the important consequence that just because a person with AD does not offer information, even when asked, does not mean that they do not know it.

Background: The effects of typical ageing on spoken language are well known: word production is disproportionately affected while syntactic processing is relatively well preserved. Little is known however about how ageing affects reading. Aims: What effect does ageing have on written language processing? In particular, how does it affect our ability to read words? How does it affect phonological awareness (our ability to manipulate the sounds of our language)? Methods & Procedures: We tested 14 people with Parkinson's disease (PD), 14 typically ageing adults (TAA), and 14 healthy younger adults on a range of background neuropsychological tests and tests of phonological awareness. We then carried out an oral naming experiment where we manipulated consistency, and a nonword repetition task where we manipulated the word-likeness of the nonwords. Outcomes & Results: We find that normal ageing causes individuals to become mildly phonologically dyslexic in that people have difficulty pronouncing nonwords. People with Parkinson's disease perform particularly poorly on language tasks involving oral naming and metalinguistic processing. We also find that ageing causes difficulty in repeating nonwords. We show that these problems are associated with a more general difficulty in processing phonological information, supporting the idea that language difficulties, including poorer reading in older age, can result from a general phonological deficit. Conclusions: We suggest that neurally this age-induced dyslexia is associated with frontal deterioration (and perhaps other regions) and cognitively to the loss of those executive processes Running head: Ageing MAKES US DYSLEXIC 2 that enable us to manipulate spoken and written language. We discuss implications for therapy and treatment.

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