Title: Thinking in Words
Description: The relationship between language and thought has long been a topic of interest and controversy in cognitive science. In this dissertation, I address one aspect of this issue: when is language present during internal thought? Simple introspection tells us that we sometimes use inner speech, but is this the exception or the rule? Using eye-tracking measures, we investigated whether infants, children and adults implicitly activate verbal labels while silently looking at pictures of objects. In the first study, 4-year-olds, 7-year-olds and adults completed a working memory task. While the two older age groups spontaneously chose a verbal encoding strategy for the pictoral stimuli, the 4-year-olds did not, suggesting a late emergence for implicit language use. The second study, however, challenges this conclusion as we find evidence for spontaneous implicit verbal activation in 24-month-old infants during free-viewing of pictures of familiar objects. The final study provides a more detailed look at the nature of the implicit verbal representations that are activated in adults during visual image processing. Unlike the 24-month-old infants, and unlike adults engaged in a working memory task, adults in this visual image processing task did not robustly activate phonological representations but did show some evidence of lexical activation, perhaps at a more abstract level of representation. Taken together, these results suggest that: 1) even very young children spontaneously engage inner speech, 2) adults and children use implicit verbal labeling in different ways, and 3) different tasks can evoke different levels of implicit verbal activation.