There is an interesting gene known as COMT that appears to modulate the ease with which people can switch tasks, by regulating the amount of dopamine in the prefrontal cortex. COMT carries instructions to the brain for how to make an enzyme (in this case, catechol-O-methyltransferase, hence the abbreviation COMT) that helps the prefrontal cortex to maintain optimal levels of dopamine and noradrenaline, the neurochemicals critical to paying attention.
