The psychology of thinking has traditionally been in the business of making comparisons between different groups of people. On the whole, these comparisons have rendered a substantial body of knowledge; but all too often, they have suffered the pitfalls of faulty organizational logic and unfounded or invidious conclusions. In this extraordinarily clear and critical introduction, Michael Cole and Barbara Means Jay out the problems involved in comparing how people think. They show, for example, how variables confounded with the constitution of two groups can lead to the wrong interpretation of group differences. More subtly, they demonstrate how cognitive differences between groups can destroy the equivalence of the tests used to make comparisons. They also discuss the unfortunate way that observed differences between groups have led to prejudicial interpretations in which mental differences are transformed into mental deficits. Cole and Means illustrate all these problems with a rich variety of examples drawn from the research literature in comparative cognition. Because they use real examples. Cole and Means offer much more than the usual banal remedies for improving research design. Instead of merely telling the student to run the right control groups, for example, they show how theory enters into the selection of appropriate controls and how atheoretic comparative work can easily run amok. It is a rare event when seasoned researchers take time to tell the novice how to avoid the problems of previous research. "Comparative Studies of How People Think" provides just such an event.