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Helen Fisher, believes we evolved three systems related to matters of the heart: the first deals with lust, the second with romantic love – also known as attraction, obsessive love or 'being in love' – and the third with attachment. Fisher's theory is that the three systems motivate us, respectively, to mate, focus our attention on a particular partner, and stick with that partner long enough to look after the children we may have.
Fisher discusses many of the feelings of intense romantic love, saying it begins as the beloved takes on "special meaning." Then you focus intensely on him or her. People can list what they don't like about a sweetheart, but they sweep these things aside and focus on what they adore. Intense energy, elation, mood swings, emotional dependence, separation anxiety, possessiveness, physical reactions including a pounding heart, shortness of breath, and craving, Fisher reports, are all central to this feeling. But the most important one is obsessive thinking.
She also think that romantic love is a very strong drive, stronger than lust, as people are more likely to commit suicide or homicide when rejected by someone they love than when their sexual overtures fail.
A good example of this kind of behavior can be found in Shakespeare´s Romeo and Juliet:
"Romeo Montague and Juliet Capulet, of the houses of Montague and Capulet, were enemies. The story starts with members of the Capulet family, quarreling with members of the Montague. This turns into a big fight. That night, Romeo and Juliet meet at a party in the Capulet mansion, and instantly fell in love. Later that night they met in the Capulet's orchard, and plan to be married the next morning. Their union was made, but soon ruined, as Romeo was banished from Verona due to the dispute. After he leaves, Juliet learns she is to marry another man. She was devastated. The two lovers made a plan. But they both end up killing themselves because both thought that the other was already death"
But the main characteristics of romantic love is craving: an intense desire to be with a particular person, not just sexually, but emotionally. It would be nice to go to bed with them, but you would prefer them to call you on the telephone, to invite you out or to tell you that they love you. The other main characteristic is motivation. The motor in your brain begins to crank, and you want this person.
Love is a very powerful emotion, and some say that love drives you to do dumb things, some people say that love hurts and some time it does. Love causes odd tremendous feelings deep within us. It causes jealousy and hate, and drives even the most amazing people to do the craziest most unbelievable stuff.