Dear Sir

Recently C Robert Cloninger et al demonstrated a trimensional character system based on monamine neurotransmitters dopamine, serotonin and norepinephrine, producing respectively "novelty seeking", harm avoidance and reward dependence.

Extraversion on this system would be produced by high novelty seeking and low harm avoidance.

In 1963 I published a report showing that in temperate zones extraversion appeared to be seasonally distributed. I could not think of a good reason.

A little later H J Eysenck demonstrated that certain occupations were also distributed across the year by birth date.

The Hounds of Annwn fell upon us both and certainly did me out of several jobs. In Cloninger’s work we have of course the explanation. If dopamine production is fixed by inheritance then serotonin, modified by day-length or light intensity, can modulate the introversion/extraversion balance and therefore ‘character’.

I would advise any young researcher who gets an odd result after honest work to publish; whatever authority says; suffer if he must but he will be vindicated. Remember poor old Darwin!

Patrick F James

1. A Systematic Method for Clinical Description and Classification of Personality Variants. C Robert Cloninger. Arch. Gen. Psychiatry. Vol. 44. June 1987.

2. Dopamine D4 receptor (D4DE) exon III polymorphism associated with the human personality trait of novelty seeking. Richard P Ebstein et al. Nature Genetics. Vol. 12. January 1996.

3. "Psychoheliosis". Patrick James. BASRA Journal. September 1963.