Mealey 2.1

From: Stalder Kathryn (
Date: Fri May 15 1998 - 11:08:40 BST

Mealey 2.1

> Both criminality and sociopathy have a substantial heritable component,
> and this heritable component is to a large extent overlapping.

So, behaviour genetic research has established a link between
criminality and sociopathy, whereby those inherited attributes
involved in criminality are the same as those involved in sociopathy.
But what are these heritable attributes? Personality would seem to be
a prime candidate as behaviour genetic research has shown a high
heritability for it.

> Studies of twins, taken as a whole, suggest a heritability of
> approximately 0.60 for repeated commision of crimes of property.

But what exactly is the relevance of this for understanding
sociopathy? At least one twin study (Christiansen) found that there
was significant heritability for crimes of property, but no such
level of significance was achieved for violent crimes. Are we saying
that the only sort of criminality linked to sociopathy is that
relating to property offences? I think a bit more clarification is
needed regarding this link.

> Adoptive studies report significant gene-environment interactions, such
> that adoptive children with both a genetic and an environmental risk
> have a far greater risk of expressing criminal behaviour than do
> adoptees with no such risk or only one risk factor, and that increased
> risk is more than simply an additive effect of both risk factors.

It is important that the combined risk of having both a biological
parent who is a criminal as well as an adoptive parent who is a
criminal is greater than just a sum of these two risks. What are the
factors that are causing this 'jump' in risk?

> Male adoptees were more sensitive to the influence of environmental
> risk factors than were female adoptees.

Is this tantamount to saying that males are more easily led, whereas
females are more resistant to environmental influence and, for some
unidentified reason, are able to exert greater control over their

> The existence of an 'antisocial spectrum' suggests a multifactorial,
> probably polygenic, basis for sociopathy and its related phenotypes.

The conclusion that there exists such an antisocial spectrum is
based, according to Mealey, on the fact that criminality and
socipathy may share some common heritable factors. But if the
diagnosis of sociopathy is based partly on evidence of prior criminal
activity, then aren't we in danger of not explaining anything, just
saying what is 'out there'.

> According to the two-threshold model, those females who do express the
> trait (sociopathy) must have a greater overall 'dose' or 'genetic load'
> than most of the males who express the trait.

This idea of sex differences and genetic loads holds for other things
too. For example, autism is far more common in boys than in girls.
For girls to be affected they require an increased genetic load.
Also, when they are affected their symptoms are generally of a much
greater severity than the autistic symptoms manifest in boys.
Following on, does this mean that female sociopaths are 'worse'
than male sociopaths?

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