What comes next? : Investigating the neural correlates of predictability during conversation with fMRI

Sammanfattning: The notion that prediction plays a role in language processing is getting less controversial, however research and discussion is ongoing as to the nature and extent of its involvement. Previous studies have mainly focused on prediction during comprehension in restricted paradigms. The current fMRI study makes use of the information theoretic measure of surprisal to investigate the neural basis of predictability during conversation. A computational model determined surprisal for each word of 288 minutes (4.8 hours) of existing conversational data summed up over twenty-four healthy participants and a confederate. Areas sensitive to surprisal for comprehension were the bilateral superior temporal and middle temporal gyri. In production, areas sensitive to surprisal were the bilateral supplementary motor area and sensorimotor areas, importantly extending to the inferior frontal cortex in the left hemisphere. We conclude that predictability during language processing plays a role at the level of word form also during conversation. A novel finding is an asymmetry for the surprisal effects on production and comprehension, respectively. This thesis also shows the viability of combining computational and neuroscientific methods to study linguistic data from naturalistic language use.