Robert Yerkes is probably best known for his work developing the WWI Army Alpha and Beta intelligence tests or his later work with primates. Earlier in his career, however, when he served as the director of psychological research at the Boston State Psychopathic Hospital, Yerkes developed a multiple choice method for measuring ideational behaviour.

As Fuchs & Trewin describe in the winter edition of the American Journal of Psychology, Yerkes defined “ideational behaviour” as:

“a series of reactive tendencies that a person displays when confronted with solving a problem. He believed that ideational behavior was innate, yet unlike other behaviorists of the period, he also believed that behavior was more complex than “our time honored classification of activities as reflex, instinctive, impulsive, habitual, voluntary”. Yerkes understood behavior as being guided by intelligence, but intelligence could not be measured directly. By measuring ideational behavior, Yerkes hoped to obtain a better understanding of intelligence and to apply that understanding to mapping phylogenic relationships both within and between species.” (p. 645-646).

Different versions of Yerkes’ multiple choice apparatus (MCAs) were designed so that ideational behaviour could be compared between species – both animals and humans. The Peabody Museum of Natural History holds an MCA in their Historical Scientific Instruments Collection, one that was used with human participants. The MCA at the Peabody is similar to the version Yerkes described in his 1921 article “A new method of studying the ideational behavior of mentally defective and deranged as compared with normal individuals” published in the Journal of Comparative Psychology (Volume 1, Issue 5, p. 369-394) and based off research carried out in 1916.

For more information on Robert Yerkes, see his autobiography originally published in 1930 or his papers at Yale University Library.