According to a study at Princeton University, becoming a father may stimulate brain development:
‘In both first-time and experienced [marmoset] fathers with dependent offspring, the team found structural changes in the prefrontal cortex, a region of the brain important for planning and memory. In these areas the neurons showed signs of enhancement, with a greater number of connections. They also had more receptor sites for the hormone vasopressin.’
Alas, the some of the benefits seem to be temporary, and return to normal as infants mature toward independence. I certainly remember rolling my eyes at my father more and more as I got older.