Stephen Michael Kosslyn is an American psychologist who specializes in the fields of cognitive psychology and cognitive neuroscience. Until 31 December 2010 he was John Lindsley Professor of Psychology in Memory of William James and Dean of Social Science at Harvard University, having previously been chair of the Department of Psychology at Harvard University. As of 1 January 2011, he became director of the Center for Advanced Study in the Behavioral Sciences at Stanford University.
Kosslyn received his B.A. in 1970 from UCLA and his Ph.D. in 1974 from Stanford University, both in psychology. His Ph.D. advisor was Gordon Bower. His former teaching career includes Johns Hopkins and Brandeis Universities.
Kosslyn is known primarily for his research and theories on mental imagery. His theory is that, contrary to common assumption, imagery is not a unified phenomenon. Rather, it consists of a collection of distinct functions, which are responsible for different aspects of imagery. For example, he decomposes imagery into four sets of processes, responsible for generating the image (i.e., activating information stored in long-term memory and constructing a representation in short-term memory), inspecting the object in the image (e.g., by reinterpreting it), maintaining the image over time, and -- possibly -- transforming the image (e.g., by rotating it, adding or deleting parts, or changing the color). His research, which includes fMRI-imaging and similar techniques, has located some of these functions to different neural networks, some of which are in different cerebral hemispheres of the brain. For example, his laboratory demonstrated that the left half of the brain is better than the right at encoding categories and generating mental images on the basis of categories, whereas the right half of the brain is better than the left at encoding specific examples or continuous distances and at generating images that have such characteristics.
Kosslyn also works on visual display design, showing how psychological principles can be used to produce displays that can be read at a glance. Most recently, he has extended this work to showing how psychological principles of perception, memory, and comprehension can be used to make and deliver PowerPoint presentations.
He has received numerous honors for his research. These include the National Academy of Sciences Initiatives in Research Award, the Prix Jean-Louis Signoret, and two honorary doctorates (from the University of Caen, France, and the University of Paris-Descartes). He was elected to the American Academy of Arts and Sciences and the Society of Experimental Psychologists.
Kosslyn has published over 300 scientific papers and written or co-authored 15 books and edited or co-edited 13 books; his authored books include Image and Mind (1980), Ghosts in the Mind's Machine (1983), Wet Mind (1992, with Olivier Koenig), Elements of Graph Design (1994), Image and Brain (1994), The Case for Mental Imagery (2006, with Thompson and Ganis), Graph Design for the Eye and Mind (2006), Clear and to the Point: 8 Psychological Principles for Compelling PowerPoint Presentations (2007), and Better PowerPoint (2010). He is also the co-author (with Rosenberg) of the textbooks Psychology: The Brain, the Person, the World (2000, 2004), Psychology in Context (2006), Abnormal Psychology (2010), and (with Smith) Cognitive Psychology: Mind and Brain.
Kosslyn has two hobbies, playing electric bass guitar and struggling with the French language.