From H = log s(n) to conceptual framework: a short history of information

"Information" has become a widely used term in psychology, especially within cognitive psychology. However, despite its status as a technical term, the word now rarely receives explicit definition. By contrast, when information entered the vocabulary of psychologists in the late 1940s, it had an explicit mathematical definition largely derived from developments in information theory. This article examines how information entered psychology, how its meaning changed, and how it remained a technical term in the vocabulary of psychologists in the second part of the 20th century. "Information" became a term that was required to speak to ever more diverse theoretical concerns and its earliest definitions in psychology could not sustain such uses. As a consequence, "information" became a term whose technical uses became increasingly difficult to differentiate from its everyday meanings. I argue that this has not necessarily made "information" a worthless term but one whose lack of specificity may now be unsettling to some psychologists.