While working on his PhD in genetics, Lashley began a number of tests on brain tissue and the idea of localization. Lashley wanted to focus mainly on behaviors that could be observed and an easy way to do that was to study white rats in a controlled setting. A fellow researcher, Shepherd Ivory Franz, also shared the common interest of studying localization and studying only things that could be observed. Franz had already done previous work with lesions in cat brains and puzzle boxes so Lashley and Franz decided to team up and work with rats.