Understanding how speakers succeed in producing fluent speech with little conscious effort is critical not only to our understanding of the human capacity for language, it also provides insight into how injury to the brain can result in different patterns of loss to that capacity. Producing speech is an impressive mental feat. For example, even cognitively intact individuals sometimes slip up and say the wrong word (e.g., monotony instead of monogamy). How is it that most of the time speakers manage to avoid such difficulties? Building on previous work, this project proposes that speakers efficiently manage the complexity of speaking by drawing on general mental processes called executive functions. These allow speakers to "focus" mental processing, allowing them to efficiently retrieve the words they wish to speak. This project tests this hypothesis by examining how the efficiency of producing speech is related to (i) individual differences in executive functions and (ii) recent experience using executive functions in other cognitive tasks. Gaining a better understanding of the links between general and language specific mental processes may help professionals capitalize on those links in therapeutic and educational settings. For instance, recent research on bilingualism suggests that regular experience with difficult language processing--e.g., when a bilingual alternates between multiple languages may improve general cognitive control and delay the onset of dementia. Identifying which general processes are involved in speech production may therefore allow the development of cognitive control training that targets those processes--which may be used to help individuals with deficits to language production.
This research will specifically examine how particular parts of general cognitive control contribute to word retrieval during speech production. Previous work has shown that there is competition among multiple representations during word retrieval (e.g., upon seeing a picture of a CAT, the words CAT, RAT, and DOG all come to mind). This project will examine whether general control processes known as executive functions help resolve such competition. Specifically, it will investigate two executive functions that support conflict resolution: response inhibition (suppression of an automatic response to a stimulus) and interference resolution (prevention of an incorrect response when multiple options are available). The first of two studies will test whether speakers? individual differences in response inhibition and interference resolution abilities influence their picture naming performance in the context of strong competition. If the target executive functions help speakers resolve conflict among competing word-level representations, then speakers with higher control abilities should show have less trouble naming pictures in the presence of competition. Importantly, several behavioral tasks will be used to evaluate each executive function, ensuring that the executive function measures do not reflect task-specific effects. The second, parallel study will examine the causality of the relationship between the target executive functions and word retrieval using a procedure known as negative transfer. Each of three groups will receive intensive practice in non-linguistic tasks intended to 'exhaust' a specific executive function. If the target control process (e.g., response inhibition) is involved in conflict resolution during word retrieval, then negative transfer should occur, such that speakers who practiced that process have more trouble naming pictures after practice than before it.
