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Can someone with access to the book confirm whether or not that is the case, and if so whether a source is cited?
(This claim about the textbook is not evaluated in this related question; a "yes" to this question does imply a "yes" to that question, but not vice-versa.)
A group of scientists placed 5 monkeys in a cage and in the middle a ladder with bananas on top...
The experiments of Harry Harlow and his associates at the Primate Laboratory of the University of Wisconsin are described in the textbook Principles of General Psychology (1980 John Wiley and Sons)