Clayton Lewis is Professor Emeritus of Computer Science and Fellow of the Institute of Cognitive Science. He is well known for his research on evaluation methods in user interface design. Two methods to which he and his colleagues have contributed, the thinking aloud method and the cognitive walkthrough, are in regular use in software development organizations around the world. He has also contributed to cognitive assistive technology, to programming language design, to educational technology, and to cognitive theory in causal attribution and learning. He was named University of Colorado President’s Teaching Scholar in 1989, a life title signifying the University’s highest award for teaching. Lewis earned a BA in mathematics from Princeton University, an MS from MIT, for interdisciplinary study in mathematics and linguistics, and a PhD from the University of Michigan in experimental psychology. He was elected to the ACM CHI Academy in 2009, recognizing his contributions to the field of human-computer interaction. In 2011 he was further recognized by the ACM CHI Social Impact Award, for his work on technology for people with cognitive, language, and learning disabilities.