How do we fall in love? Albert Einstein said “You can’t blame gravity for falling in love”, then who do you blame? The question how do we falls in love is as long as the love itself. Let’s analyze the psychophysiological underpinnings of falling in love. Speaking in psychophysiological terms, falling in love can be a three step process:
Step 1  Attraction
Step 2  Addiction
Step 3  Attachment

Attraction is affected by different factors like proximity, sex appeal, health, resources, cultural predilections and personality types. We look for partners who are somewhat higher in Conscientiousness, Extraversion, Agreeableness, but lower in Neuroticism than ourselves. Once attraction is developed after appraising all these factors it leads to release of hormones like androgen and estrogen which are related to sexual drive and libido. Therefore evolutionarily speaking attraction leads to the act of conception of offspring which is critical for survival of species. These Psychophysiological processes make someone more or less attractive.

When we develop attraction for someone we activate certain regions in brain like ventral tegmental area (VTA), a reward region that is associated with feelings of pleasure, arousal, euphoria, focused attention, and motivation. The same area is also activated when we have cocaine, chocolate, and money. Therefore love can be as addictive as all these addictions. The activation of these areas cause the release of hormones like dopamine and norepinephrine which causes the feeling of pleasure and euphoria. In essence, dopamine’s most substantial role is to take an individual from “liking” to “wanting” a substance or another individual. With the increase in chemicals like dopamine and norepinephrine the level of serotonin is reduced. Serotonin is associated with regulating mood, appetite, memory, sleep and cognition. Low levels of serotonin is also associated with obsessive compulsive disorder (OCD). Thus we develop an obsession for our partner. Therefore when we are in love we are obsessed about and addicted to our partner. We can’t stop thinking about and can’t get enough of our partner.

After developing initial attraction and developing addiction for our partner we spend more time together which causes the release of other hormones like oxytocin and vasopressin which activates the pair bonding regions in ventral palladium, and deactivates the stress-related areas right anterior insula, superior frontal gyrus, and hypothalamus. Oxytocin is well-known for its release during childbirth and breastfeeding, but it has been more recently recognized for release during processes of social bonding, orgasm, and maternal behavior. It also facilitates trust, social bonding, and monogamy. In this way we develop attachment with each other which helps evolutionarily in upbringing the offspring.

In short we are
Attracted to people because of their personality and sex appeal.
Addicted to people because of feelings of arousal, pleasure and euphoria.
Attached to people because of trust and commitment to up bring offspring.