We’ve all heard that people favor their own kind and discriminate against out-groups—but that’s a simplistic view of prejudice, says Amy Cuddy, a professor at Harvard Business School who studies how we judge others. In recent years she and psychologists Susan Fiske of Princeton University and Peter Glick of Lawrence University have developed a powerful new model. All over the world, it turns out, people judge others on two main qualities: warmth (whether they are friendly and well intentioned) and competence (whether they have the ability to deliver on those intentions). A growing number of psychological researchers are turning their focus to this rubric, refining it and looking for ways in which we can put this new understanding of first impressions to use.

When we meet a person, we immediately and often unconsciously assess him or her for both warmth and competence. Whereas we obviously admire and help people who are both warm and competent and feel and act contemptuously toward the cold and incompetent, we respond ambivalently toward the other blends. People who are judged as competent but cold—including those in stereotyped groups such as Jews, Asians and the wealthy—provoke envy and a desire to harm, as violence against these groups has often shown. And people usually seen as warm but incompetent, such as mothers and the elderly, elicit pity and benign neglect.

New research is revealing that these split-second judgments are often wrong, however, because they rely on crude stereotypes and other mental shortcuts. Last year psychologist Nicolas Kervyn and his colleagues published studies showing how we jump to conclusions about people’s competence based on their warmth, and vice versa. When the researchers showed participants facts about two groups of people, one warm and one cold, the participants tended to assume that the warm group was less competent than the cold group; likewise, if participants knew one group to be competent and the other not, they asked questions whose answers confirmed their hunch that the first group was cold and the second warm. The upshot: “Your gain on one [trait] can be your loss on the other,” says Kervyn, now a postdoctoral researcher at Princeton.

This “compensation effect,” which occurs when we compare people rather than evaluating each one separately, runs counter to the well-known halo effect, in which someone scoring high on one quality gets higher ratings on other traits. But both effects are among several mistakes people often make in inferring warmth and competence. We see high-status individuals as competent even if their status was an accident of birth. And when we judge warmth, rivalry plays a role: “If someone is competing with you, you assume they’re a bad person,” Cuddy says.

The good news is that if you belong to a stereotyped group or otherwise know how people see you, you can try changing your image. A competent politician who strikes the public as cold, for example, can draw on his warmth reserves to better connect with voters. After all, Cuddy points out, “Everybody comes across as warm or competent in some area of their lives.”