Love is one of the most complex phenomena that we human beings are capable of feeling. This peculiar feeling has made people wonder how and why it happens. Science has also dealt with this phenomenon, and one of the best known researchers in this line of research is Helen Fisher , a biologist and anthropologist who has spent more than 30 years trying to understand it.

Helen Fisher’s research

To try to explain this complex feeling, Fisher focused on trying to figure out the brain mechanisms that are involved in the process of falling in love and love . To do this, he subjected several subjects who were madly in love to fMRI scans in order to find out which areas of the brain are activated when the subject thinks of his loved one.

Loving” and neutral photographs

To conduct the tests, Helen asked study participants to bring two photographs: one of the loved one and another one that had no special meaning, i.e. a neutral face . Then, once the person was introduced into the brain scanner, the photograph of the loved one was first shown on the screen for a few seconds while the scanner recorded the blood flow in different regions of the brain.

Individuals were then asked to look at a random number, and then had to subtract it from seven, and then look at the neutral photograph where a scan would be done again. This was repeated several times to obtain a significant number of images of the brain to ensure consistency of what was obtained while looking at both photographs.

The results of the research

Many parts of the brain were activated in the lovers who were part of the experiment. However, it seems that there are two regions that have a special importance in the sublime experience of being in love.

Perhaps the most important discovery was the activity of the caudate nucleus . This is a large, C-shaped region that is very close to the center of our brain. It is primitive; it forms part of what is known as the reptilian brain, because this region evolved long before the proliferation of mammals, some sixty-five million years ago. Scans showed that there were parts of the body and tail of the caudate nucleus that became especially active when a lover looked at a picture of his lover.

The brain’s reward system is important in falling in love

Scientists have long known that this brain region directs body movement. But until recently they have not discovered that this huge motor is part of the brain’s “reward system” , the mental network that controls sexual arousal, feelings of pleasure and motivation to achieve rewards. And what is the neurotransmitter that is released during activation of the caudate nucleus? Dopamine, a substance that is very involved in motivation, that is, it helps us to detect and perceive a reward, discriminate between several of them and wait for one of them. It generates the motivation to achieve a reward and plans the specific movements to achieve it. The leader is also associated with the act of paying attention and learning.

This study also found activity in other regions of the reward system, including the septum and ventral tegmental area (VTA). The latter region is also associated with the release of a huge amount of dopamine and norepinephrine, which is distributed throughout the brain, including the caudate nucleus.When this occurs, attention narrows, the person appears to have more energy, and may experience feelings of euphoria and even mania .

The conception of love from this research

From her study, Helen Fisher radically changed the way of thinking about love. Love was once considered to involve a range of different emotions from euphoria to despair. After this study, it is concluded that love is a powerful motivational system, a basic impulse for matching . But why is it an impulse and not an emotion (or a range of emotions)?

  • It is difficult for passion to disappear like any other impulse (hunger, thirst, etc), and it is also complicated to control. Unlike emotions that come and go.
  • Romantic love focuses on obtaining the gratification of a specific reward: the loved one. In contrast, emotions are linked to an infinite number of objects, such as fear, which is associated with darkness or being assaulted.
  • There is no differentiated facial expression for romantic love , other than the basic emotions. All basic emotions have an expression on the face that is specific only during the irruption of that emotion.
  • Last but not least, romantic love is a need, an anxiety , an impulse to be with the loved one.

The Chemical Cascade of Love

Everything I have described is related to what would be romantic love (or infatuation), that which is felt in the first moments when we become obsessed with the loved one. For Helen Fisher, romantic love evolved in the brain to focus all our attention and motivation on one specific person. But it doesn’t end there. To make love more complex, this brain system that generates a force as intense as romantic love is also intrinsically related to two other basic impulses for mating : the sexual impulse (desire) and the need to establish deep bonds with the partner (attachment).

Sexual desire is what allows an individual to perpetuate the species through reproduction with an individual of the opposite sex. The hormones involved in this impulse are androgens, composed of estrogen, although it is primarily testosterone that is most involved in this function, in both men and women. The areas that are activated in the brain when the sex drive exists are: the anterior cingulate cortex, other subcortical regions, and the hypothalamus (involved in testosterone release).

In the case of romantic love, as we discussed, it is related to focusing attention on one individual at a time, in a way that saves time and energy for courtship. The neurotransmitter par excellence is dopamine, although it is accompanied by norepinephrine and a decrease in serotonin. The areas that are functional to this system are: mainly the caudate nucleus and at the same time the ventral tegmental area, the insula, the anterior cingulate cortex and the hippocampus.

Attachment and its relationship to oxytocin and vasopressin

And finally, as the couple tightens the bond and deepens their relationship, attachment emerges, a system that has the function of allowing two individuals to tolerate each other , at least long enough to achieve parenting during childhood. It is closely related to the decrease of dopamine and norepinephrine, which leads to a considerable increase in two hormones that allow such function: oxytocin and vasopressin. The neural circuits that produce such neurotransmitters are the hypothalamus and the gonads.

Each of these three brain systems evolved to fulfill a specific mating function. Desire evolved to allow sexual reproduction with almost any more or less suitable partner. Romantic love enabled individuals to focus on only one partner at a time, thereby saving considerable time and energy for courtship. And attachment resulted in men and women being together long enough to raise a child during childhood.

The heart is in the brain

Regardless of the fact that in general such systems appear the way they have been explained (sexual desire, romantic love and finally attachment), it does not always happen in this order. Some friendships (attachment) over the years awaken a deep love that can lead to love or a friendship ruined by a broken heart. It is even possible to feel sexual attraction for one person, romantic love for another and a deep attachment for a different one . This theory opens up a question mark when trying to explain a behavior as interesting as unwanted in a relationship, infidelity.

In short, it is interesting that we are getting closer to understanding how such a small mass of only 1.3 kg, i.e. the brain, can generate something as complex as love, an impulse so strong as to be the subject of so many songs, novels, poems, stories and legends.

Bibliographic references:

  • Fisher, H. (2004). Why We Love: The Nature and Chemistry of Romantic Love. Santa Fe e Bogotá: Taurus Pensamiento
  • Fisher, H. (1994) Anatomy of Love: A Natural History of Monogamy, Adultery and Divorce. Barcelona: Anagram
  • Fisher, H. [TED]. (2007, January 16). Helen Fisher talks about why we love and cheat [Video file].Retrieved from
  • Pfaff, D. (1999), DRIVE: Neurobiological and Molecular Mechanisms of Sexual Motivation, Cambridge, Mass.: The MIT Press.