Hermann Ebbinghaus

Discovered the Spacing effect, one of the founders of experimental psychology and the methodology which preceded Cognitive psychology; see Ebbinghaus, H. (1913). Memory: A Contribution to Experimental Psychology (H. A. Ruger & C. E. Bussenius, Trans.). (Original work published 1885) for more.

Ebbinghaus’s experiments were important to psychology because they demonstrated that {mental phenomena could be reliably quantified and studied}.

Q. When was Ebbinghaus’s seminal book on memory published?
A. 1885