This chapter describes how methods fit into a more general way of viewing psychological research. In cognitive psychology the situation has often been looked at as a purely methodological issue. Social psychologists have shown how cognitions, behaviours, and measures of personality all vary according to the situation. Sometimes the importance of the materials, people, or situation is less obvious or critical, but they can always be identified. Much psychological research is done with different populations, instruments and situations. The professional participants emerge who take part in all the studies thereby reaping the financial benefits of supply-side economics. According to G. Cohen, “ecological validity has become something of a catchword” in psychology. Ecological materials are those that are encountered in normal daily lives and/or those for which people have developed to process both as individuals during their lifetimes and as a species throughout evolution.