The think-aloud method was introduced in the usability field by Clayton Lewis[1] while he was at IBM, and is explained in Task-Centered User Interface Design: A Practical Introduction by Lewis and John Rieman.[2] The method was developed based on the techniques of protocol analysis by K. Ericsson and H. Simon.[3][4][5] However, there are some significant differences between the way Ericsson and Simon propose that protocols be conducted and how they are actually conducted by usability practitioners, as noted by Ted Boren and Judith Ramey.