Why do we fall in love

What is Love?

Romantic love both exhilarates and motivates us. It is also critical to the continuation of our species. Without the attachment of romantic love, we would live in an entirely different society that more closely resembled some (but not all) of those social circles in the animal world. The chemicals that race around in our brain when we're in love serve several purposes, and the primary goal is the continuation of our species. Those chemicals are what make us want to form families and have children. Once we have children, those chemicals change to encourage us to stay together to raise those children. So in a sense, love really is a chemical addiction that occurs to keep us reproducing.

We all have a template for the ideal partner buried somewhere in our subconscious. It is this love map that decides which person in that crowded room catches our eye. But how is this template formed?

Appearance

Many researchers have speculated that we tend to go for members of the opposite sex who remind us of our parents. Some have even found that we tend to be attracted to those who remind us of ourselves. In fact, cognitive psychologist David Perrett, at the University of St. Andrews in Scotland, did an experiment in which he morphed a digitized photo of the subject's own face into a face of the opposite sex. Then, he had the subject select from a series of photos which one he or she found most attractive. According to Dr. Perrett, his subjects always preferred the morphed version of their own face (and they didn't recognize it as their own).

Personality
Like appearance, we tend to form preferences for those who remind us of our parents (or others close to us through childhood) because of their personality, sense of humor, likes and dislikes, etc.

Pheromones
The debated topic of human pheromones still carries some weight in the field of love research. The word "pheromone" comes from the Greek words pherein and hormone, meaning "excitement carrier".

In the animal world, pheromones are individual scent "prints" found in urine or sweat that dictate sexual behavior and attract the opposite sex. They help animals identify each other and choose a mate with an immune system different enough from their own to ensure healthy offspring. They have a special organ in their noses called the vomeronasal organ (VNO) that detects this odorless chemical.

The existence of human pheromones was discovered in 1986 by scientists at the Chemical Senses Center in Philadelphia and its counterpart in France. They found these chemicals in human sweat. A human VNO has also been found in some, but not all, people. Even if the VNO isn't present in all of us -- and may not be working in those who do have it -- there is still evidence that smell is an important aspect of love (note the booming perfume industry). An experiment was conducted where a group of females smelled the unwashed tee shirts of a group of sweaty males, and each had to select the one to whom she was most "attracted." Just like inthe animal world, the majority of the females chose a shirt from the male whose immune system was the most different from their own. 
 

Staring Into Each Other's Eyes

Professor Arthur Aron, of the State University of New York at Stonybrook, has studied what happens when people fall in love and has found that simply staring into each other's eyes has tremendous impact. In an experiment he conducted, Professor Aron put strangers of the opposite sex together for 90 minutes and had them discuss intimate details about themselves. He then had them stare into each other's eyes for four minutes without talking. The results? Many of the subjects felt a deep attraction for their partner after the experiment, and two even ended up getting married six months later.