Feature

Move over "fight-or-flight"--there's a new paradigm in town, the first new model to describe people's stress response patterns in more than 60 years.

The model, called "tend-and-befriend" by its developers, won't replace fight-or-flight. Rather, it adds another dimension to the stress-response arsenal, says University of California, Los Angeles, psychologist Shelley Taylor, PhD, who, along with five colleagues, developed the model.

In particular, they propose that females respond to stressful situations by protecting themselves and their young through nurturing behaviors--the "tend" part of the model--and forming alliances with a larger social group, particularly among women--the "befriend" part of the model. Males, in contrast, show less of a tendency toward tending and befriending, sticking more to the fight-or-flight response, they suggest.

The researchers describe this new model in an upcoming issue of Psychological Review, supporting their premise by pulling together existing evidence from research with nonhuman animals, neuroendocrine studies and human-based social psychology.

The tend-and-befriend model fills what Taylor sees as a huge gap in the stress response literature: namely, that almost all the studies have been conducted in males and so, therefore, upheld fight-or-flight as the main response to stress.

The tend-and-befriend response, in contrast, fits better the way females respond to stress. It builds on the brain's attachment/caregiving system, which counteracts the metabolic activity associated with the traditional fight-or-flight stress response--increased heart rate, blood pressure and cortisol levels--and leads to nurturing and affiliative behavior.

The research findings used to support the model are not new, says University of Chicago psychologist John Cacioppo, PhD, but the way they've been integrated is.

"The data supporting the model look very compelling," says Cacioppo, who has studied the biology of stress in animals and humans. "Even if it's wrong, which I don't think it will be, it's a very powerful model."

What's more, the model is sure to inspire thousands of new studies designed to test its claims, from whether women truly do respond to stress by tending and befriending, to questions about the specific hormonal and neuroendocrine systems responsible for the response to the specific contexts in which such a system may be triggered, adds psychologist Nancy Collins, PhD, who studies human reactions to stressful situations. The model can serve as a foundation on which to build an entirely new body of research, she says.

Culling the evidence

Taylor and her colleagues developed their model after listening to a lecture on stress responses in rats. The description of fight-or-flight in response to stress didn't fit any of the findings Taylor had seen in almost 30 years as a health psychologist studying people's reactions to stressful life events.

When she began discussing the issue with her laboratory staff, postdoc Laura Klein, PhD, pointed out that the findings heard about at the lecture had been heavily based on studies of male animals.

"It was like a big light went on," says Taylor, who developed the new model with Klein, now at Pennsylvania State University, Brian Lewis, PhD, now at Syracuse University, Regan Gurung, PhD, now at the University of Wisconsin, Green Bay, and graduate students Tara Gruenewald and John Updegraff.

Women, they speculated, may have developed a completely different system for coping with stress in large part because their responses evolved in the context of being the primary caregiver of their children. To find support for their theory, they pulled together data from previously unconnected sources.

From research into the neuroendocrine responses responsible for fight-or-flight, for example, they document that, although women do show the same immediate hormonal and sympathetic nervous system response to acute stress, other factors intervene to make fight-or-flight less likely in females.

In terms of the fight response, while male aggression appears to be regulated by androgen hormones, such as testosterone, and linked to sympathetic reactivity and hostility, female aggression isn't. Instead, female aggression appears to be more cerebral in nature--moderated by social circumstances, learning, culture and the situation--and in animals "confined to situations requiring defense," write the researchers.

In terms of flight, fleeing too readily at any sign of danger would put a female's offspring at risk, a response that might reduce her reproductive success in evolutionary terms. Consistent with this idea, studies in rats suggest there may be a physiological response to stress that inhibits flight. This response is the release of the hormone oxytocin, which enhances relaxation, reduces fearfulness and decreases the stress responses typical to the fight-or-flight response.

So rather than fight or flee, Taylor and her colleagues posit, women often tend and befriend, an idea supported by several lines of research in humans and other animals. Some of the more intriguing work, says Taylor, comes out of Michael Meaney's laboratory at McGill University. He and his colleagues remove rat pups from their nest for brief periods--a stressful situation for pups and mothers--and then return them to the nest and watch what happens. The mothers immediately move to nurture and soothe their pups by licking, grooming and nursing them. This kind of tending response stimulates the growth of the pups' stress-regulatory system.

What stimulates this behavior in the mother? Taylor and her colleagues suggest that it's governed in part by oxytocin. Studies in many different animals, including non-human primates and humans, show that oxytocin promotes caregiving behavior and underlies attachment between mothers and their infants. In addition, some studies have found that mothers tend to be more nurturing and caring toward their children when they are most stressed.

As for the idea of "befriending" when stressed, Taylor and her colleagues detail evidence from rodent studies and studies in humans that when they are stressed, females prefer being with others, especially other females, while males don't. Indeed, in humans, women are much more likely than men to seek out and use social support in all types of stressful situations, including over health-related concerns, relationship problems and work-related conflicts.

"It is one of the most robust gender differences in adult human behavior," write Taylor and her colleagues.

Again, oxytocin may be at play, they suggest. In female prairie voles, for example, injections of oxytocin enhance social contact and inhibit aggression. The same may occur in males, but males are less likely than females to have naturally high levels of oxytocin.

One of a repertoire of responses

Although the tend-and-befriend model emphasizes gender differences, the researchers reject the idea that gender stereotypes are written in our genes. Indeed, Taylor doesn't see biological models of behavior as inherently constraining--rather, they help tie human behavior to other species and provide a framework for general behavioral tendencies. The fun, she says, will be teasing apart how our biological predispositions unfold in the context of real-life experience.

Both Collins and Cacioppo hope that means researchers will examine social context to figure out which situations may promote tend-and-befriend and which might, instead, promote fight-or-flight or even as yet undiscovered stress responses.

In fact, tend-and-befriend may be just as adaptive for men as for women in certain contexts, says Collins, whose research finds no gender differences when examining how often husbands and wives seek support from their most intimate companions--for example, each other.

"Perhaps these gender differences are adaptive with acute stressors," says Collins. "But when you think of longer term stressors, such as hunger, it doesn't make sense to have these gender differences. Men and women need social networks to work it out."

The most adaptive system would be one in which men and women select from a repertoire of responses depending on the specific stressor, she says.

Adds Taylor: Mainstream stress researchers "have been very quick to study behaviors like aggression and withdrawal and have failed to notice very important behaviors like affiliation. We think it's cute when women call up their sisters when they're under stress. But no one has realized that that is a contemporaneous manifestation of one of the oldest biological systems. Our focus on fight-or-flight has kept us from recognizing that there are systems that are as old as fight-or-flight that are tremendously important."