Measuring the Mind: Replication in Early Psychological Experimentation (1890-1925)

My talk starts with some general definition of the term “replication” and remarks on the historiography about experimentation, recalling the discussion about this feature of scientific practice in the works of Shapin & Schaffer; Collins, Galison, etc. But in these works, no mention is made on how psychologists became concerned and used replication. Already Kant, who examined the possibility of psychology becoming a real science, had mentioned as one obstacle the non-replicability of psychological introspection. Therefore, for Wundt and his colleagues the demonstration of psychological experiments being replicated was crucial. In my talk, I will a) expose views on replication and replicability expressed by leading psychologists such as Wundt, Titchener, Watson and Dunlap; b) offer examples and compare how this tool was used in some empirical studies in connection with psychological methods (e.g. introspection, association experiments and mental testing), and c) examine the role replication played in controversies of the time. The examination of historical sources shows what scientists in the past understood by “replication” and why they thought that this should be part of the process of knowledge construction. I conclude that replication gained historical prominence, as soon as the main objective of psychological research was to identify laws. In general, it seems that the debates about replication deepened consciousness of psychologists about problematic aspects of psychological experimentation (in general), influencing the standards of scientific research.