Here's what they found:

The "Friendly and Conventional" region. The first region features the states of Middle America, including South Dakota, Nebraska, and Iowa, known as the "red" states. People here ranked highly in levels of extraversion, agreeableness, and conscientiousness, moderately low in neuroticism, and very low in openness. Residents of the region tend to be "sociable, considerate, dutiful, and traditional," the researchers write. They are predominantly white with low levels of education, wealth, and social tolerance, and tend to be more religious and politically conservative than people outside of the region. They are also less healthy compared with other Americans.

The "Relaxed and Creative" region. The second cluster consists of West Coast states, Washington, Oregon, and California. Its personality profile is marked by low extraversion and agreeableness, very low neuroticism, and very high openness. Cultural diversity and alternative lifestyles are high, and residents are politically liberal and healthy, both mentally and physically. This region is richer, has more residents with college degrees, and is more innovative than other areas. These states cast fewer votes for conservative presidential candidates and are less religious compared with others. Here, the study's authors write, people value tolerance, individualism, and happiness.

The "Temperamental and Uninhibited" region. The third and final grouping comprises of mid-Atlantic and Northeast states like Maine, Pennsylvania, and New York—the "blue" states. The region is low in extraversion, very low in agreeableness and conscientiousness, very high in neuroticism, and moderately high in openness. People here, the researchers say, are "reserved, aloof, impulsive, irritable, and inquisitive." Residents are politically liberal and less religious, and are disproportionately college-educated individuals, older adults, and women. A good chunk of the "passionate" and "competitive" residents are leaving the area, according to census data, and heading south or southwest.

So why do researchers care about what people are like across America? Because personality traits on their own, rather than the usually cited factors like religion, racial diversity, education, or wealth, could help explain the country's differing political views. "In left-leaning regions, it appears that residents are generally open, reserved, and socially distant, whereas in right-leaning regions, residents appear to be friendly, warm, dutiful, and traditional," the researchers write. The separation of blue states into two distinct psychological regions suggests that "there are distinct psychological profiles differentiating East Coast from West Coast liberals."

Regional personality traits could also tell researchers a lot about economic prosperity and health. States high in openness and low in neuroticism show greater economic success and innovation. Nine of the 11 states that comprise a southeastern region dubbed the Stroke Belt for its unusually high incidence of strokes are located in the "friendly and conventional" cluster, which rates low in well-being and healthy behavior. People living in the "relaxed and creative" region, on the other hand, are in good health.

But as is the case with most personality research, it is tough to state with absolute certainty which came first—people open to experience or a good economy, conventional attitudes or poor health—and what's having an effect on what.