Attraction, attachment, being in love: These topics have all been fodder for magazine articles in publications as varied as Nature, The Knot and Cosmopolitan. In fact, multiple UC Davis researchers have been quoted in hundreds of stories to talk about the science of love. Turns out, most people — and many animal species — are geared toward pairing up. And life — and often, living well and healthy — depends on these bonds. At UC Davis multiple labs are investigating these unions. 

1. The psychology behind commitment and attachment

“A deep, fundamental truth about humans is that we have a powerful need to belong,” said Paul Eastwick, professor of psychology who leads the attraction and relationships research laboratory, one of a collection of similar labs on campus focused on relationship research. 

“To thrive, we need to feel that we are appreciated and supported, and that someone else has our back,” he said. One primary way that people meet this need to belong is by forming pair bonds with sexual partners.”

Eastwick, who came to UC Davis in 2016, penned a new book, Bonded by Evolution: The New Science of Love and Connection (Crown, 2026) in which he explains what happens when the mist of desirability wears off and compatibility has the chance to chart lasting love and happiness. The book argues in part that lasting love isn't about finding a "perfect" match based on traits like beauty or status, but about building compatibility through shared experiences and creating a secure attachment over time.

Every relationship has its own idiosyncratic culture, or a set of “patterns, rituals and in-jokes that shape daily life,” he said in a recent New York Times article, which explored whether “love languages” were necessary to the success of a relationship. 

He suggested, instead, that the way that two people construct their own tiny culture, “can be a huge source of joy in a relationship.”

2. Advancing attachment theory

For Phil Shaver, UC Davis professor of psychology emeritus, his early serious research about couple bonding happened a few years before he came to UC Davis in 1992. He had co-authored a study on romantic love advancing “attachment theory” as not only a bonding that occurs between mothers and children but also in adult relationships. In the world of psychology, the theory transformed the study of interpersonal relationships. Much of the relationship research, continuing today was relatively new in the 1980s and grew from there.

Shaver went on to study and lecture worldwide on his theories throughout his career, receiving shortly before his retirement the "Legacy" award from the Society of Personality and Social Psychology for lifetime achievement in the field.

Since then, UC Davis faculty have measured heart rates and respiration, calculated the levels of cortisol in couples, and observed in dozens of studies how human couples, even how primates and prairie voles pair up. 

3. Physical changes that come with relationships

A study by Professor Emilio Ferrer in 2011 found that couples in romantic relationships showed synchronized heart rates and breathing patterns just by sitting near each other. The researchers also mixed up the data from the couples. When the two individuals were not from the same couple, their hearts did not show synchrony, nor did their breathing closely match. And perhaps most interesting, women were more likely to adjust to their male partner’s heartbeats and breathing than were men. Additional researchers have advanced this theory in newer studies. 

Ferrer has also researched and written about how couples who stay in sync through various difficult — and happy — times in their lives can preserve their bond. Those who don’t, break up.

4. Older couples: healthier together

When older couples experience positive emotions together in everyday life, they have lower levels of the stress hormone cortisol, according to a study by Tomiko Yoneda, assistant professor of psychology. “While brief increases in cortisol are normal, consistently higher levels over time are thought to signal strain on the body and have been linked to poorer health in other studies,” she said. One of her studies on this topic was published last year. 

That study’s findings underscored the “importance of fostering positive shared emotions in close relationships, which may promote better physical health for older adults,” said Yoneda.

Yoneda investigates the links between personality and cognitive aging, as well as the mechanisms underlying these relationships, particularly the interplay between personality and physiological factors. 

5. Relationships: Understanding stories in context

Dulce Wilkinson Westberg, assistant professor of psychology, studies how people make sense of their identities, relationships and social worlds through the stories they tell. In research published during her doctoral training at UC Riverside, she examined romantic infidelity from the perspectives of both victims and perpetrators, finding that the meaning of infidelity narratives depends heavily on context and perspective.

At UC Davis, her research focuses on life narratives related to social groups including race, ethnicity, gender and social class. In one recent study, she found that women, compared with men, told more negative stories about race, gender, and social class and drew more personal meaning from those experiences. Westberg said these findings “highlight the combined effects of racism and sexism on identity formation.” 

Her latest work, now awaiting publication, explores how young adults of color conceptualized “being American” during President Trump’s first administration. She said this study “underscores the complexity of national identity among youth of color who are navigating what it means to be American amid sociopolitical conflict.”  

6. More than animal instinct

Professor Karen Bales, director of the California National Primate Research Center, has looked at pair bonding in animals on numerous occasions. She has worked with prairie voles, titi monkeys and seahorses — all species in which males and females form pair bonds and males help in pre- and post-natal care of infants. In particular, she is interested in the role of neuropeptides such as oxytocin and vasopressin in these behaviors, as well as the effects of early experiences on the development of these behaviors.

Social bonds are essential for some species to reproduce and survive, yet not all species form pair bonds. It is likely that in species where resources are distributed and females have to space out, a single male ends up living with a single female. Over evolutionary time, it is possible that coordination between the pair mates results in better survival of their offspring — leading to more representation in the population for the offspring of "better-bonded" pairs. These bonds can include both affiliation (grooming, contact) as well as other psychological effects like the ability of the pair mates to help each other regulate stress. These behaviors all have consequences for health.

"As humans, we are also a pair-bonding species,” Bales said. “The consequences of loneliness on our health are as large as the effects of smoking, diet or exercise. So we need to pay good attention to not just our pair bonds, but all of our social relationships."