A recent study from Indiana University found that the taste of beer–even without the alcohol–triggers rewards in the brain that drives you to crave more beer.
To measure the pleasure response, the scientists looked at dopamine release in the brain. The scientists studied 49 men with varying relationships to alcohol (from non-drinkers to heavy drinkers) and found that from the first tiny sip of beer, the brain responded with a dopamine increase in an area of the brain called the ventrial striatum. This dopamine release corresponded with the men reporting increased cravings for more beer. The experiment was conducted in a way that could not make them men intoxicated, so the response was attributed solely to the taste molecules in the beer.
You can read a more in-depth article about this study at Discover.