or izing " ▁to ▁explore ▁empir ically ▁the ▁basic ▁dimensions ▁of ▁person ality , ▁motiv ation , ▁and ▁cogn itive ▁ab ilities . ▁One ▁of ▁the ▁results ▁of ▁C att ell ' s ▁application ▁of ▁factor ▁analysis ▁was ▁his ▁discovery ▁of ▁ 1 6 ▁separate ▁primary ▁trait ▁factors ▁within ▁the ▁normal ▁person ality ▁sphere ▁( based ▁on ▁the ▁trait ▁lex icon ). ▁He ▁called ▁these ▁factors ▁" source ▁tra its ". ▁This ▁theory ▁of ▁person ality ▁factors ▁and ▁the ▁self - report ▁instrument ▁used ▁to ▁measure ▁them ▁are ▁known ▁respectively ▁as ▁the ▁ 1 6 ▁person ality ▁factor ▁model ▁and ▁the ▁ 1 6 PF ▁Question naire ▁( 1 6 PF ). ▁ ▁C att ell ▁also ▁under to ok ▁a ▁series ▁of ▁empir ical ▁studies ▁into ▁the ▁basic ▁dimensions ▁of ▁other ▁psych ological ▁domains : ▁intelligence , ▁motiv ation , ▁career ▁assess ment ▁and ▁voc ational ▁interests . ▁C att ell ▁the or ized ▁the ▁existence ▁of ▁fluid ▁and ▁cry st all ized ▁intelligence ▁to ▁explain ▁human ▁cogn itive ▁ability , ▁investig ated ▁changes ▁in ▁G f ▁and ▁G c ▁over ▁the ▁lif es pan , ▁and ▁constructed ▁the ▁Culture ▁Fair ▁Int elligence ▁Test ▁to ▁minim ize ▁the ▁bias ▁of ▁written ▁language ▁and ▁cultural ▁background ▁in ▁intelligence ▁testing . ▁ ▁In nov ations ▁and ▁accomplish ments ▁C att ell ' s ▁research ▁was ▁mainly ▁in ▁person ality , ▁ab ilities , ▁motiv ations , ▁and ▁innov ative ▁mult ivari ate ▁research ▁methods ▁and ▁statistical ▁analysis ▁( es pecially ▁his ▁many ▁ref in