This little blurb was in the July 2000 Cats&kittens magazine. They give their source as The Daily Oklahoman:
“Can your cat make you smarter? Perhaps, but not as much as your fish can. A survey conducted by the American Pet Product Manuracturers Association revealed that owners of dogs, cats, or fish scored considerably above average on the Standard Aptitude Test than non-pet owning students did. The survey, conducted among 200 students ranging in age from 14 to 24, also revealed that fish owners scored highest in assessments of math and verbal skills. Their combined scores were 200 points above all non-pet owners’ scores.”
(Is that second sentence rather confusing? I didn’t write this, only copied it!)