Friday, 4 May 2012

G determines everything

Ok, maybe not everything. But if you're stuck in prison, and you have a higher IQ, you're less likely to be involved in a violent incident. And, if you're lucky enough to be assigned to a higher-IQ cell-block, you're also safer. Here's the press release and here's the article now published in Intelligence.
There is a long tradition of theoretical and empirical research linking intelligence to criminal activity. At the same time, the extant literature has been slow to examine this relationship in other settings. One such setting in which this relationship may also manifest is the prison environment, where knowledge on the determinants of prison misconduct has important implications for prison management and security. Drawing from a representative sample of inmates from a large Southern state in the US, the current study presents the first assessment of the relationship between intelligence and prison misconduct. The effect of intelligence, measured via the WAIS-R, on violent prison misconduct is analyzed controlling for inmate and prison-level factors. Results indicated that the individual's IQ, as well as the average IQ of the prison unit, was significantly and negatively related to violent prison misconduct. Implications and directions for future research are highlighted.
Here's the main result:
A one standard deviation increase in IQ score (as compared to other inmates within the same prison unit) was associated with a ten percent reduction in the odds of committing violent misconduct.
...average IQ of the prisoners within each of the 30 different prison units was found to have a significant effect on the likelihood of an inmate committing violent misconduct. Simply stated, individuals housed in a unit with a higher average IQ score were significantly less likely to engage in violent misconduct. 
Another fun fact from the study: mean IQ in the inmate sample is 90 as compared to 100 in the national sample. People who try to estimate the social costs of alcohol-related crime by extrapolating from non-inmate average wage rates are massively overstating the potential earnings of the prison cohort.

This may also give us an alternative potential explanation for why some public schools fare badly on conduct measures.


  1. As per several posts over chez moi, IQ is huge.

    However, it's not necessarily the top factor determining stuff.

    In order of predictivity...

    1. Self-control/patience -- marshmellow test
    2. Self-efficacy -- Bandura -- how much you believe (honestly, not lie about) you can do.
    3(tie) IQ
    3(tie) Conscientiousness -- Big 5 personality trait.
    4. Attractiveness?

    I personally believe that blood serum testosterone levels would beat any of those for generic predictability, but I haven't yet found someone to design an experiment to prove me right.

  2. I am surprised that Eric does not enquire of Aretae the value of
    " design an experiment to prove me right"
    Anyone who already knows the outcome can make good experiment.
    I once proved that grasshopper has ten legs, because I was interested and believe in that.
    The same way as feminist believed about one man in four,