There are surely many people who, when they first drank coffee, felt, "I simply can't stand the bitterness that lingers on my tongue." This is the kind of bitter taste the brain instinctively tries to avoid. Yet, just as many people love drinking coffee, there are plenty of people who come to prefer bitter flavors. Recent research has revealed that this may be due to the action of the neurotransmitter dopamine. Scientists finally discover why we learn to l