I have taken the pre-1994 SAT. While it is true that there are some vocabulary words on the pre-1995 SAT which are archaic, the three words that you mentioned (cacophonous, equanimity and harried) actually do not fall in that category. I think that "people with a higher IQ" tend to be more well-read and thus have a larger vocabulary and perhaps some understanding/knowledge of roots/prefixes/suffixes to aid in deriving meaning as well. Some test takers did study/cram vocabulary although I don't believe that was anywhere as effective as being well-read.
