This pseudo-syl logism lay at the heart of what was perce ived b y m a n y as a dark age of perceptual research dur ing the m i d 20th century. Instead, the foundat ion empir ic is t assumptions of the t radi t ional behavior is t enterprise were interpreted to mean that expl ic i t behavior a n d the changes i n behavior o c c u r r i n g as a result of experience (i.e., studies of learning) s h o u l d be the m a i n objects of s tudy for a scientif ic psychology .