Your dad's brain...

Most of us have long suspected that being a father messes with your head. Now scientists have verified our fears.

So how does fatherhood create these changes? Gould's group found that fatherhood increased the number of receptors in the prefrontal cortex for arginine vasopressin, a peptide hormone involved in the formation of social bonds. They propose that the resulting increase in vasopressin signaling could have caused the increases in dendritic spines. Their previous enrichment work, meanwhile, indicates that behavioral changes that go with fatherhood could also contribute to the observed spine changes. Interestingly, they provide evidence that the abundance of vasopressin receptors was reduced over time as infants aged -- suggesting that this particular change is temporary and driven by recent contact with infants. A comparable examination of whether the spines also tended to decrease over time, in parallel with the reduction in vasopressin receptors, would have been informative. If the increases in dendritic spines demonstrated more permanence, the case for the experience of fatherhood as a form of enrichment would be strengthened. [More]

It gets more complicated. Vasopressin is the "monogamy hormone":

Sometimes it takes a while for scientific research to filter down to the great mass of society, and even longer for the appropriate action to be taken. Today's example: a seminal (so to speak) study, published in Nature in mid-2004, about two species of vole -- one in which the male is monogamous, one in which he plays the gigolo. Scientists identified and extracted the monogamy hormone, vasopressin, from the loyal prarie vole, and bred it into the cheatin' meadow vole (above). Result: the male meadow vole, fortified with vasopressin, stopped fooling around, settled down with his beloved, and raised the little voles right.
The news caused a minor stir when it first came out. Then it started cropping up in popular science books, such as last year's bestseller, The Female Brain. And in the future ... well, it's not too much of a stretch to imagine that women are going to want to carry vasopressin around in their purse in easy-to-apply pill form, is it? Vasopressin is already available in pharmacies, and is often used therapeutically. It won't be long before every bar-hopping woman on the planet is going to want a vasopressin test, or better yet, a vasopressin roofie to slip into some smooth-talking lothario's drink. [More]

I suppose it could be that simple. Men are pretty straightforward humans. And while it can creep you out to realize strange chemicals can change the way you think, try not to worry too much.

Relax. Have a beer.