▁two . ▁Watson ▁hoped ▁to ▁learn ▁to ▁predict ▁and ▁control ▁behavior ▁through ▁his ▁research . ▁The ▁popular ▁H ull - Sp ence ▁stim ulus - response ▁approach ▁was , ▁according ▁to ▁George ▁Mand ler , ▁impossible ▁to ▁use ▁to ▁research ▁topics ▁that ▁held ▁the ▁interest ▁of ▁cogn itive ▁scient ists , ▁like ▁memory ▁and ▁thought , ▁because ▁both ▁the ▁stim ulus ▁and ▁the ▁response ▁were ▁thought ▁of ▁as ▁completely ▁physical ▁events . ▁Be havior ists ▁typically ▁did ▁not ▁research ▁these ▁subjects . ▁B . ▁F . ▁Sk inner , ▁a ▁functional ist ▁behavior ist , ▁critic ized ▁certain ▁mental ▁concepts ▁like ▁instinct ▁as ▁" ex plan atory ▁fiction ( s ), " ▁ideas ▁that ▁assume ▁more ▁than ▁humans ▁actually ▁know ▁about ▁a ▁mental ▁concept . ▁Vari ous ▁types ▁of ▁behavior ists ▁had ▁different ▁views ▁on ▁the ▁exact ▁role ▁( if ▁any ) ▁that ▁conscious ness ▁and ▁cogn ition ▁played ▁in ▁behavior . ▁Although ▁behavior ism ▁was ▁popular ▁in ▁the ▁United ▁States , ▁Europe ▁was ▁not ▁particularly ▁influenced ▁by ▁it , ▁and ▁research ▁on ▁cogn ition ▁could ▁easily ▁be ▁found ▁in ▁Europe ▁during ▁this ▁time . ▁ ▁No am ▁Ch om sky ▁has ▁fr amed ▁the ▁cogn itive ▁and ▁behavior ist ▁positions ▁as ▁rational ist ▁and ▁empir ic ist , ▁respectively , ▁which ▁are ▁philosoph ical ▁positions ▁that ▁arose ▁long ▁before ▁behavior ism ▁became ▁popular ▁and ▁the ▁cogn itive ▁revolution ▁occurred . ▁Emp ir ic ists ▁believe ▁that ▁human ▁ac quire ▁knowledge ▁only ▁through ▁sens ory ▁input , ▁while ▁rational ists ▁believe ▁that ▁there