John B. Watson
The philosophical psychology prevalent before the end of the 19th century relied heavily on introspection. The speculations concerning the mind based on those observations were criticized by the pioneering advocates of a more scientific and objective approach to psychology, such as William James and the behaviorists Edward Thorndike, Clark Hull, John B. Watson, and B. F. Skinner. However, not everyone agrees that introspection is intrinsically problematic, such as Francisco Varela, who has trained experimental participants in the structured "introspection" of phenomenological reduction.