The criminologist Brie Diamond from the University of Texas at Dallas made a very interesting discovery about prisoners in jail (Diamond, B. et al, 2012).  She got hold of data about the intelligence of a large sample of prisoners in the US prison system.  She identified cell blocks as high IQ, Medium IQ and Low IQ by averaging the cognitive ability of the prisoners in them.  She found that:

  • Low IQ cell blocks had the greatest amount of violence
  • Medium IQ cell blocks had a medium amount of violence
  • High IQ cell blocks had the lowest amount of violence

This bears out years of research showing this link in various ways in various workplaces.  So, if you have a low IQ does this mean that you are violent?  At an individual level, no, but in a population such as workforce it is a good idea to:

  1. Test Intelligence and factor it into your hiring decisions. It is one of the best predictors of success and failure at work we have ever found.
  2. Make sure all employees have non violent personalities, including characteristics such as low levels of anger, high levels of self control, and a liking and respect for other people. Click here to find out how.


Andrew Marty
Managing Director


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Brie Diamond, Robert G. Morris, J.C. Barnes, Individual and group IQ predict inmate violence, Intelligence, Volume 40, Issue 2, March–April 2012, Pages 115-122, ISSN 0160-2896,

Andrew Marty