The Greeks recognized that in an arranged marriage between a man and a woman, once authorized by society they could often develop eros by having sèxûal relations. They noted that this often evolved to produce philia and agape. Yet the Greeks often allowed that even faithfully married men might engage in eros with other men or young boys. The vision of unified forms of love restricted to married partners was embedded in the mores and laws of many cultures.
Writers over the centuries have tied to understand, amplify and explain the various aspects of love and suggest exemplary situations to both avoid and emulate.
Only in the last decades of the 20th Century has science began to develop techniques for studying both the brains of other animals and the workings of human minds. The early evidence suggests there may in fact be at least three distinct processes in human brains involved with developing loving relationships with others. While not a perfect match with the distinctions proposed by the ancient Greeks, there are similarities and parallels.
toleratingthat which is required to maintain long term relationships. Partner attachment evolved to motivate mating individuals to remain together long enough to perform species specific useful parental duties.
The is characterized by the urge for sèxûal gratification. It is associated with the androgens in many primates, especially humans. Humans with higher circulating levels of testosterone tend to engage in more sèxûal activity. The drive is not exclusive and attracts us to a wide range of partners. Such activity which results can trigger the brain to spike the concentration of the neurotransmitter dopamine which in turn can cause romantic love to ensue.
Romantic love focuses on a different goal than sèx drive, emotional union with another. Romantic love involves an elevated concentration of dopamine in the participant's brain. It provides a simple, very possessive motivation, an obsessive craving to be exclusively with the other person emotionally. While love was former thought to be an emotion, it is not. It is a drive which results from activity in many regions of the brain involved with motivation. Romantic love has been observed to be universal in humans across all cultures and includes observed characteristics of increased energy, focused attention, obsessive following, affiliative gestures, possessive mate guarding, goal-oriented behaviors and motivation to win a preferred mating partner. Romantic love begins as an individual starts to regard another individual as special and unique. The lover then focuses his/her attention on the beloved, aggrandizing the beloved's worthy traits and overlooking or minimizing his/her flaws. The lover expresses increased energy, ecstasy when the love affair is going well and mood swings into despair during times of adversity. Adversity and barriers heighten romantic passion, what has been referred to as frustration attraction. The lover suffers separation anxiety when apart from the beloved and a host of sympathetic nervous system reactions when with the beloved, including sweating and a pounding heart. Lovers are emotionally dependent; they change their priorities and daily habits to remain in contact with and/or impress the beloved. Romantic love is also involuntary, difficult to control and generally impermanent.
Attachment has been described as companionate love, a feeling of happy togetherness with someone whose life has become deeply entwined with your live. Such a sense of attachment involves increased concentration of oxytocin and vasopressin. It provides a calming sense of security of togetherness. Oxytocin (nine amino acid structure at right →) is thought to be produced and released in the brain during hugging, touching, and ôrganism in both genders. Oxytocin is involved in social recognition and bonding, and creating generosity and the formation of trust between people. The structure of oxytocin is very similar to that of vasopressin whose structure differs from oxytocin by just two amino acids (Arginine replacing Leucine here second from left and Phenylalanine replacing Isoleucine middle right). Both have a ring structure closed by a disulfide (S:S) bridge. Vasopressin has been implicated in both short and long term memory formation, including forming images and delayed reflexes. Experimental studies in several species suggest that vasopressin released into the brain during sèxual activity, initiates and sustains patterns of activity that support the pair-bond between the sèxual partners and in a male to induce aggression towards other males. Earlier research did not distinguish between romantic love and attachment. However many cultures have long made the distinction. Recent brain imaging investigations in humans and animal studies suggest that the brain processes for attachment are in fact distinct from those for intense romantic love.
The androgens which are central to the sèx drive and these gonadal and adrenal hormones have not been associated with human romantic love. Moreover, when humans self-administer androgens to boost sèx drive, they do not report that they fall in love. This suggest that these two neural systems do not always act in tandem in Homo sapiens. Although the neural regions associated with the sèx drive overlap those associated with courtship attraction, these two neural systems show many differences, suggesting that the primary brain system for the sèx drive is distinct from the brain system associated with human romantic love. While there are many well known examples of individuals engaged in sèxual activity with others for whom they felt no romantic love and many have also been in love with someone with whom they have had no physical contact, the brain systems for the sèx drive and courtship attraction often coincide. Animal studies indicate that elevated activity of dopamine pathways can stimulate a cascade of reactions, including the release of testosterone and oestrogen. Likewise, increasing levels of testosterone and oestrogen promote dopamine release