Statistics and physiology: why getting it right matters


With recent advances in brain imaging and gene mapping we have significantly more data to help us understand human behavior. For example, we can see how folks with PTSD react to triggers using SPECT scans. We can understand how some folks have genetic markers that indicate a propensity for certain kinds of addictive behavior.

Enter this news story on NPR about one researcher who discovered he had the brain scan of a sociopathic killer–the very kind of people he was studying.

It is essential that we understand how to interpret these kinds of studies that often make the news. I am not an expert in brain scanning but let’s review a simple statistical principle. If you evaluate that 100% of people who have a particular problem (in this case sociopathic murder) have a particular brain scan signature, what can you say about its application to the general public? NOTHING. You cannot say, yet, that having that brain scan signature puts you at risk for becoming a murderer. What we need to know is whether or not that brain scan exists in the general public. I am willing to bet that if we did a large-scale study, we would find that 99% (maybe even higher) of those with a similar signature would NOT be killers. Thus, we cannot predict anything on the basis of the scan.

A similar (non) relationship exists between childhood abuse and becoming a child abuser. Yes, when we research pedophiles we find a high correlation between childhood sexual abuse and those who are in prison. But, when we look at the general public and victims of sexual abuse, we find that less than 1/2 of 1% go on to abuse others. Thus, abuse victims are not likely to become abusers.

However, these studies are not meaningless. In the case of the underactive frontal/orbital lobe, we do see certain features often present in individuals with ADHD: impulsivity, emotional lability, ego-centrism, lesser ability to learn from mistakes, difficulties in planning and forethought, etc. Rather than try to predict big events (like murder), we might use these kinds of studies to understand the common experiences and activity of those with a particular signature. This does not absolve people of responsibility or suggest they cannot make changes in how they operate. But, it might help us grow in understanding that what might be easy for one person may be more difficult for another. Just like we would want to give someone with dyslexia more time to read and comprehend a piece of literature, we might want to make some allowances for someone with a quiet frontal lobe.

It might mean that we understand that everyone thinks thoughts that ought not be repeated but that some have a harder time not saying it. And in the case of those “some”, we might be more willing to cut them slack even while we call them to account for saying what they say.

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Filed under counseling, Psychology

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