- Karl Spencer Lashley (1890–1958) : Karl Lashley is the American neuropsychologist who was one of the first to combine behavioral sophistication in experiments with neurologic sophistication, thereby creating the field of Experimental neuropsychology. Likewise, Karl Spencer Lashley was an early supporter of Watsonian behaviorism who eventually left the behavioristic camp when his neurological research failed to support the switchboard conception of the brain upon which behaviorism was based.