That won't come as any surprise to anybody with more than one kid, but the relationship to brain anatomy is interesting. Steve Connor reports:
Personality types are linked with structural differences in the brain - which could explain why one child grows up to be impulsive and outgoing while another becomes diligent and introspective.
Anatomical differences between the brains of 85 people have been measured and linked with the four main categories of personality types as defined by psychiatrists using a clinically recognised system of character evaluation....
Brain scans that measure differences in volume down to an accuracy of less than one cubic millimetre found, for instance, that people defined as novelty-seeking personalities had a structurally bigger area of the brain above the eye sockets, known as the inferior part of the frontal lobe.
If this holds up (and I'm singularly unable to judge — owing to my lack of 3-d processing power, I never been able to make head nor tail of any article referring to a region in the brain. No doubt my brain region that contributes to 3-d thinking is vanishingly small.)
I’ve long felt we are programmed by evolution to have kids with different personalities as a form of what financial economists like Edward M. Miller call ”portfolio diversity:” you don’t want to put all your assets into one basket, such as mortgage backed securities. For example, Genghis Khan’s aggressive personality worked out fine from a Darwinian standpoint (his personal genetic signature appears in a huge number of people across a giant swath of Eurasia), but it probably got lots of other guys with similar personalities killed early. So, you wouldn’t want to have three sons each with Genghis Khan’s personality. They'd just end up skewering each other.
But my more scientist friends roll their eyes when I advocate portfolio diversity and say that’s ”group selectionism,” which has been thoroughly exploded.