Halloween is coming up, so my posts are going to start getting scarier. It’s long been noted that criminals have lower IQ’s than non-criminals, and that psychotics have lower IQ than non-psychotics, so it’s only logical to assume that people who are criminally psychotic would have especially low IQ’s.
How low? Let’s begin with the fact that criminals average IQ’s 10 points lower than the non-criminal population. If we assume the United States has an average IQ of 97, then criminal Americans should have an average IQ of 87. Now it’s known that premorbid schizophrenics average IQ’s 9 points lower than matched controls. I don’t know how closely matched these matched controls are but assuming they are identical in all other ways except schizophrenia (which of course they’re not), we should expect schizophrenic criminals to have premorbid IQ’s 9 points lower than non-schizophrenic criminals. But since in rare cases, schizophrenia actually causes crime, the two variables are obviously not 100% independent, so let’s say schizophrenic criminals have pre-morbid IQ’s only 5 points lower than non-schizophrenic criminals. This implies an average IQ of 82. However once schizophrenia emerges, average IQ drops by 6 points, so their IQ’s would be reduced to 76.