Humans are a highly sexual species, and we have a strong need for physical from onward. In contrast to most other animals that only have for reproduction, humans use sex as a means for intimately bonding with others. In this respect, we’re quite similar to our chimpanzee and bonobo cousins, in that they also use sex mainly for recreation rather than procreation. But unlike our promiscuous primate brethren, humans commonly seek out long-term sex partners.

Among human monogamous couples, some keep the same sex partner for their entire life. And in modern society lifelong is still held up as the ideal. But in reality, most of us are serial monogamists. That is, we enter into a committed relationship, break up sometime later, and then enter into another committed relationship.

Monogamy, whether lifelong or serial, provides several benefits. For one thing, having a committed partner provides us with stability in life as well as a reliable source of emotional support. It also protects us from the spread of sexually transmitted infections (STIs).

Despite this, many people engage in sexual behaviors that put them at risk for STIs. Two risky behaviors that have been much studied in the field include having multiple concurrent sex partners and engaging in sex without condoms. Either one of these behaviors increases the chance of acquiring an STI, and sex becomes especially risky when people do both.

So why do people engage in risky sexual behaviors even when they fully understand the dangers? This is the question that the University of Southern California researchers Hye Min Kim and Lynn Carol Miller explored in a recent article published in the journal Health Psychology.

Plenty of research has already been published on this topic, but the results so far have been contradictory. To bring some clarity to this issue, Kim and Miller conducted a meta-analysis of the existing literature. This is a technique that culls the data from multiple studies, treating them as if they were the results of a single large experiment.

In the field of relationship science, theory has become a powerful tool for analyzing the dynamics of intimate relationships. This theory proposes that the emotional bonds infants develop with their caregivers serve as working models for their later relationships, and in particular those with significant others.

Studies indicate that about two-thirds of American infants develop a secure attachment with their caregivers. Their mothers are responsive to their needs, and they learn both that they are worthy of love and that others are dependable sources of love.

However, the other third of American infants seem to learn that their mothers aren’t very responsive to their needs, and as a result, develop an insecure attachment. Some infants learn they can only get their mother’s if they’re extremely demanding, and this is known as attachment. Others learn to self-soothe instead and develop avoidant attachment.

Attachment differences have been researched in adults, too. Anxiously attached adults are clingy, needy, and distrustful in their intimate relationships. They often unwittingly drive away their significant others, which may only reinforce their belief that they’re unworthy of love. In contrast, avoidantly attached adults tend to eschew deep emotional connections with others. They see others as unreliable sources of love, and so what relationships they do have tend to be shallow.

Kim and Miller hypothesized that attachment style would be an important factor driving the pursuit of risky sexual behaviors. Specifically, they predicted that securely attached adults would tend to form long-term monogamous relationships, while insecurely attached adults would be more likely to have multiple concurrent sex partners and engage in condom-less sex. The result of their meta-analysis supported this hypothesis, but with an interesting twist.

The key finding was that insecurely attached adults, whether of the anxious or avoidant type, tended to have more lifetime sex partners and were more likely to have concurrent sex partners than those who were securely attached. This observation meshes well with the abundance of data showing that secure attachment is a key factor in successful monogamy. It seems that insecurely attached adults have more lifetime sex partners—at least in part—because they’re largely unsuccessful at maintaining long-term monogamous relationships.

However, when it comes to having sex without condoms, insecurely attached adults diverged based on how they were categorized. Adults with avoidant attachment generally practiced “safer” sex, in that they used condoms during promiscuous sex. In contrast, anxiously attached adults were more willing to have intercourse without condoms, despite the known risk of STIs.

These findings fall in line with what is already known about the characteristics of the various attachment styles. Securely attached adults tend to have a positive sense of self as worthy of love and they trust others to reliably supply that love. They have the emotional reserve to weather the inevitable difficulties that will arise in marriage.

Insecurely attached adults, in contrast, don’t trust others to provide the love they need. Those with anxious attachment often feel unworthy of love, so they’re more willing to put their own safety at risk to gain any sort of intimate connection with others. For this reason, they may be more willing to have unprotected sex if that’s what their current partner demands.

Conversely, those with an avoidant attachment style may willingly enter into multiple relationships in order to extract whatever sexual pleasure they can, but they’re not willing to put their own health at risk. So they practice safer sex within their promiscuous lifestyle.

Kim and Miller note that these findings should be of special interest to public health officials. Simply educating the public on the dangers of unprotected sex and the best practices of those who engage in safer sex isn’t enough. This is because some people—including, it seems, those who can be described as anxiously attached—simply don’t care much about protecting their sexual health as long as they can attract partners who can temporarily meet their intimacy needs. As is so often the case, more research is needed to find effective ways of promoting safer sex among this population.

Fcebook image: Anatoliy Cherkas/Shutterstock