The Extended Mind: The Power of Thinking Outside the Brain

by Annie Murphy Paul

Kenneth Koedinger, a professor at Carnegie Mellon University and the director of its Pittsburgh Science of Learning Center, estimates that experts are able to articulate only about 30 percent of what they know. His conclusion is based on research like the following: A study that asked expert trauma surgeons to describe how they insert a shunt into the femoral artery (the large blood vessel in the upper leg) reported that the surgeons neglected to cite nearly 70 percent of the actions they performed during the procedure. A study of expert experimental psychologists found that they omitted or inaccurately characterized an average of 75 percent of the steps they took when designing experiments and analyzing data. And a study of expert computer programmers revealed that they enumerated fewer than half of the tasks they actually carried out when debugging a computer program.