Most of us consider ourselves to be objective, consistent people who make decisions that reflect our core principles, no matter what the situation. In “Situations Matter,” psychology professor Sam Sommers throws this common-sense notion out the window. Our environments are actually much more powerful than we think.

Statistics show that people are more likely to marry someone who lives in the same neighborhood than someone from farther away. And the idea that women are more nurturing and less aggressive by nature? An experiment that allowed women to anonymously blow their opponents away during video games showed that they were just as trigger-happy as the male participants. Our perceptions, both of ourselves and of the actions of others, are heavily influenced by context. We are, Sommers suggests, unconscious of the way that different scenarios can manipulate our seemingly objective understanding.

To give weight to his argument, Sommers offers evidence from numerous experiments. For example, an adrenaline-filled chance encounter engineered by psychologists to take place between a man and a beautiful woman on a rickety suspension bridge led to greater attraction than a similar meeting on a sturdier bridge. (Planners of first dates take note: To make a lasting connection, a horror film may be a better bet than a comedy.) More disturbing are his examples of how being part of a crowd can lead us to apathy, or to fail to lend a helping hand. This has had fatal results, such as when 38 bystanders witnessed 2-year-old British toddler James Bulger being beaten and dragged around town by two sadistic 10-year-olds who later murdered him. In crowds, we are less likely to act independently, assuming someone else will step up. In a group, we are also more likely to obey authority figures, even when what is asked of us defies basic morality (think Abu Ghraib).

Sommers challenges the pop wisdom that we should strive to locate an authentic self. This view, he suggests, may lead to complacency. A series of experiments with college students in Hong Kong showed that those who believed their basic intelligence was fixed and could not be changed were less likely to seek ways to improve themselves, or to persist after poor academic performances. Instead, Sommers recommends we embrace the idea of a flexible self, accepting “that the ‘authentic’ self isn’t some sort of Holy Grail, unless by the analogy you mean that you aren’t sure of whether or not it even exists in the first place.”

Not surprisingly, our beliefs about gender expectations also depend on context. Not only do we push gender-appropriate colors and toys on our children from birth, but we also tend to stretch our assumptions about biology, with potentially devastating results for girls in our society. Remember Teen Talk Barbie, who said, “Math class is tough!” when you pressed a button on her back? Societal influences are stronger than we think. In one experiment, men and women performed equally well after taking a math test that they were told had no gender bias. In another group given the same test with no instructions, men outperformed women three to one. As a corrective, Sommers offers a number of useful suggestions for parents and educators to consider in interacting with children, “the most impressionable and malleable of us all.”

’Situations Matter: Understanding How Context Transforms Your World’ by Sam Sommers (Riverhead. 290 pp. $25.95). (Riverhead)

The idea that the one ideal love of our lives is out there somewhere, waiting for that magical moment of fate and coincidence to find us, is another cultural myth that Sommers dispels. The familiar face is more likely to become a romantic partner than the mysterious stranger. In one experiment in a large lecture course, the instructor arranged for attractive women not enrolled in the course to sit through varying numbers of classes. At the end of the semester, participants rated the woman who’d attended the greatest number of classes as the one to whom they were most attracted. Finding Mr. or Ms. Right, Sommers says, may therefore be as simple as becoming that familiar face, perhaps by moving into a highly visible apartment near the stairs. “The increased foot traffic may be detrimental to your sleep schedule and carpet wear,” he writes, “but it can work wonders for your social life.”

Sommers suggests that we can use the power of context to our advantage, whether to become better Samaritans, better leaders or better manipulators. By simply being attuned to our environment, we are already well on our way to shaping circumstances to our advantage. “Situations Matter” offers a blend of weighty and whimsical insights that makes for a thought-provoking and entertaining read.

Rachel Newcomb is an associate professor of anthropology at Rollins College and the author of “Women of Fes: Ambiguities of Urban Life in Morocco.”

SITUATIONS MATTER

Understanding How Context Transforms Your World

By Sam Sommers

Riverhead. 290 pp. $25.95