French, J. W. (1940). Trial and error learning in paramecium. Journal of Experimental Psychology, 26(6), 609-613.
http://dx.doi.org/10.1037/h0059015
Data are presented which show that when paramecia are repeatedly enclosed in a glass tube which allows free turning, the average escape time decreases in successive trials. The modification in behavior is not related to general activity and seems best understood in terms of learning. (PsycINFO Database Record (c) 2016 APA, all rights reserved)