There is also research suggesting that pedophiles suffer from some sort of neurological disturbance or brain damage. Again, there is some evidence of this. Several brain imaging studies have suggested abnormal brain function. There have also been cases of people developing pedophilia after suffering brain damage. However, this research is complicated by the samples used in pedophile studies. Most studies obtain their subjects from the criminal justice system. In other words, we study the ones who get caught. We rarely study the ones who have never been caught or have never acted on their urges. We know that, on the whole, convicted criminals tend to have lower intelligence, more problems with impulse control, and higher levels of psychopathic personality traits than the general population. Therefore, it is not clear if the biological findings are related to pedophilia per se, or to other problems common with a criminal population.