I think they are implying that people with lower intelligence are more likely to be in jail. There's at least three reasons why I would consider this very plausible:
1. Intelligence is associated with higher impulse control.
2. Intelligent criminals are probably less likely to be caught. They might also have a better chance at working to lower their sentences after being caught.
3. It is harder to be successful with a lower IQ (although I would posit it is far from the most important factor), and economic hardship is strongly correlated with crime.
1. Intelligence is associated with higher impulse control.
2. Intelligent criminals are probably less likely to be caught. They might also have a better chance at working to lower their sentences after being caught.
3. It is harder to be successful with a lower IQ (although I would posit it is far from the most important factor), and economic hardship is strongly correlated with crime.