A death of a scientist is occasion to reflect on the role of behavioral research in the design of telecom devices. It is not so much that Mr. Karlin trained midcentury Americans how to use the telephone. It is, rather, that by studying the psychological capabilities and limitations of ordinary people, he trained the telephone, then a rapidly proliferating but still fairly novel technology, to assume optimal form for use by midcentury Americans. “He was the one who introduced the notion that behavioral sciences could answer some questions about telephone design,” Ed Israelski, an engineer who worked under Mr.