A science is only as good as its methods. Physiological psychology presents a range of major methodological challenges, and how well we meet these challenges affects the ease with which we can interpret the experiments that we carry out Some of these challenges are entirely technical but others are conceptual, stemming from the fact that most methods only make sense if one makes certain assumptions about the brain which may, or may not, be valid. There is nothing alarming or unusual about methodological problems; all sciences have them and it is quite common for the questions that people ask to run ahead of the techniques available for answering them. It is also quite common for theoretical predictions to go untested for want of appropriate experimental methods. The important point is to recognize that these method ological difficulties exist and allow awareness of them to influence our interpretation of experimental results.