Love is both complicated and intuitive at the same time. Chances are, you aren’t sketching out graphs to decide whether “this feeling” you have constitutes as love. Because you don’t have to. Because the exhilaration and preoccupation is telling enough; because you feel warm, and giddy, and inflated with euphoria.

While love can be explained through the range of emotions it spans, it may also be approached in a more objective manner. In the research paper “Lust, Attraction, and Attachment in Mammalian Reproduction,” Helen E. Fisher at Rutgers University dissects the process of love into (you guessed it) three stages: lust, attraction, and attachment; where each stage is “associated with a discrete constellation of neural correlates, and each evolved to direct a specific aspect of reproduction.”

Lust, according to Fisher, is the most inclusive. “[It] motivates individuals to seek sexual gratification with any conspecific.” Higher levels of hormones such as androgens and estrogens yield higher proclivities to lust.

Lust parallels many aspects of the next stage: attraction. However, while the stages are in fact closely connected, humans may experience lust without also experiencing romantic attraction, and vice versa. Fisher writes that “the attraction system, associated primarily with the catecholamines, motivates individuals to focus their mating effort on preferred conspecifics.” In the attraction stage, factors like “symmetry, the display of resources, the display of fertility[,] timing, state of health, access to resources, childhood experiences, and myriad other cultural and biological forces” catalyze feelings of attraction, while sensations like “increased energy and intent focus” encourage the process.

“In humans, attraction is meditated by a host of cultural stimuli. When an individual falls in love, where they fall in love, with whom they fall in love, how the court, even whether they choose to act on their bodily sensations of attraction can be expected to be influenced by childhood experiences, by myriad other cultural forces, and by individual volition.”

Ms. Margaret Brosnan, who teaches AP Biology and Genetics at ERHS, offered a biological perspective on attraction. “[Generally], like attracts like…people are more likely to be attracted to people who look like them.” Of course, she added, the prospect of harmful recessive genetic disorders would ideally deter people from consanguineous relationships. Animals, especially, have specific “ways to outbreed…with elephants, the oldest females remember all the males that were born to [a certain] group of elephants, and if she sees a male that she knows, she’ll run them off, because that male is related to some of the other elephants in this herd.” Dolphins are another example – “every dolphin who meets another dolphin says hello, and they have what’s called a signature whistle [that] always ends, in the last notes, [with] their mother’s. Now, that only works on the maternal [side]…but there’s something programmed within them to not mate with close relatives.”

The catecholamine dopamine plays a huge role in the onset and maintenance of attraction. Effects of increased dopamine include euphoria, motivation, hyperactivity, increased mental activity, and decreased need for sleep – sensations all associated with passionate attraction. Interestingly, low levels of serotonin, which are known to cause inflictions such as insomnia and eating disorders such as anorexia, are also associated with attraction. “Low levels of central serotonin may contribute to obsessive “intrusive thinking,” a primary element of passionate love,” Fisher explains. “In general, however, high levels of central serotonin have been associated with the consummatory and satiating aspects of sexual behaviors and a loss of sexual interest.”

Attachment is quite distinct from lust and attraction. While the previous two stages are interrelated and perhaps, at times, even difficult to differentiate, the neural correlates involved in attraction do not often intersect that of any other stage. Neuroscientists consider attachment as a form of “consummatory behavior,” which may refer to monogamous behaviors between the opposite sex as well as parenting behaviors. “In humans, the…behavioral patterns associated with attachment are accompanied by reported feelings of closeness, security, peace, social comfort, mild euphoria, and reduced anxiety when in contact with a partner, and separation anxiety when apart for a length of time.” Fisher cites arranged marriages and stable marriages as instances of attachment: “Spouses in [these] marriages regularly maintain attachment to one another, express feelings of attachment to one another, and display mutual parental duties without displaying or reporting feelings of attracting or sexual desire for one another.”

Individuals may, of course, experience the three emotion systems differently. Factors like biology and environment may be responsible for these discrepancies. Lust, attraction, and attachment are discrete stages of love, but they “can also be expected to be closely interrelated and to work in concert with one another and with other bodily systems.”