Every time we speak, we're improvising. "Humans possess a remarkable ability to talk about almost anything, sometimes putting words together into never-before-spoken or -written sentences," said Morten H. Christiansen, the William R. Kenan, Jr. Professor of Psychology in the College of Arts and Sciences. We can improvise new sentences so readily, language scientists believe, because we have acquired mental representations of the patterns of language that allow us to combine words into sentences. The nature of those patterns and how they work, however, remains a puzzle in cognitive science, Christiansen said.