Some recurrent issues in the history of behavioral sciences.

Many issues seem to have appeared, disappeared, and reappeared in the behavioral sciences during the 20th century. Salient examples discussed in the present paper are consciousness, including the concept itself and consciousness in nonhuman animals; the method of introspection; and cognition, including the interpretation of mental imagery and the role of language in thinking. One possible explanation of the apparent cycles is consistent with a suggestion by John B. Watson: Important issues are found to be intractable and are abandoned, but they recur when newer theories and methods emerge.