Foundations Of Cognitive Science

Protocol Analysis

Protocol analysis is one experimental method that can be used to gather intermediate state evidence concerning the procedures used by a system to compute a function. In protocol analysis, subjects are trained to think aloud as they solve a problem, and their verbal behaviour forms the basic data to be analyzed. The first step of a protocol analysis is to obtain, and then transcribe, a verbal protocol. The next step is to take the protocol and use it to infer the subject's problem space (i.e., infer the rules being used, as well as various knowledge states concerning the problem). The third step is to create a problem behaviour graph, which reflects state transitions as subjects search through the problem space in their attempt to solve the problem. Finally, the problem behavior graph is used to create a computer simulation (typically created as a production system) that will solve the problem. By comparing, in detail, the behaviour of the simulation to the verbal protocol, one can validate the assumptions that led to the program's creation. In turn, the program provides a rich description of an individual's processing steps, and transitions in knowledge,during the problem-solving process.


  1. Ericsson, K.A., & Simon, H.A. (1984). Protocol analysis: Verbal reports as data. Cambridge, MA: MIT Press.
  2. Newell, A., & Simon, H.A. (1972). Human problem solving. Englewood Cliffs, NJ: Prentice-Hall.