E pluribus unum—“Out of many, one”—was the first official motto of the United States, adopted by the founding fathers and enshrined in the nation’s Great Seal in 1782. In its statement of unity, it exemplifies the differences inherent in the United States—a fitting description for a singular nation defined by innumerable internal divergence. Yet, few organizing principles exist to explain these differences, which find their expression in divergent ecologies, histories, average personality traits, and various state outcomes. Why, for instance, is the incidence of illicit substance use greater in states like Hawaii, Alaska, and New Hampshire relative to Mississippi, Ohio, and Oklahoma, but incidents of discrimination much higher in the latter than the former? Why do states like Colorado and Connecticut exhibit traits associated with greater impulsivity and greater tolerance, while other states, such as Alabama and Kansas, exhibit the opposite patterns? What might shed light on the difference in anti-immigrant attitudes between Arizona and New York, states with similarly large populations of illegal immigrants? In all, what does this seemingly diverse and wide array of state-level differences have in common?

Although the United States is often parsed on a red versus blue dichotomy, our lab suggested another framework by which to understand differences amongst the states in a paper published in the Proceedings of the National Academy of Sciences: states vary in terms of their tightness or looseness, which captures whether states have strong norms and little tolerance for deviance (tight) or weak norms and greater tolerance. As anyone who has traveled widely in the United States can attest, the range of behavior across states is incredibly diverse. Finding a singing cowboy playing the guitar in his underwear may indeed be a hard thing to find outside of New York City, for instance. In this study, we document not only how states vary in tightness-looseness, but why they vary—in large part based on the ecological and historical differences between the states.

The strategy of examining how cultures vary harkens back as far as Herodotus in his classic, Histories. More recently, Geert Hofstede greatly spurred these efforts with the publication of his book Culture’s Consequences, detailing the extent to which certain values (for instance, collectivism versus individualism) are endorsed across nations. More recently, we have broadened the toolkit even more and begun to study how cultures vary beyond values. For instance, we showed that cultures vary in the strength of social norms (i.e., tightness) across 33 nations and demonstrated that this cultural dimension is distinct from the various value dimensions proposed by Hofstede and others (e.g., the GLOBE research project). Consistent with the idea that cultural differences often arise from differences in ecological and historical conditions, we found that tight countries have experienced a wide range of ecological and historical threats whereas loose countries experienced fewer. The strong norms that characterize tight nations help humans coordinate their social action in the face of numerous survival threats.  Loose nations can ”afford” more latitude and permissiveness because they face far fewer natural and human made threats.

In this study, we wanted to see whether tightness, and its predictors and outcomes, could be applied to the state level. We reasoned that while the U.S. is generally a loose culture, we might find that there is wide variation in tightness across the 50 states. For inspiration, we drew on Vandello and Cohen’s classic study which created an index of state level collectivism using archival data and we created a new index that measures the strength of norms and punishments across the states.

Check out the map of tightness to diagnose where your state is. Tighter states—those with stronger rules and greater punishment for deviance—are located primarily in the South and the Midwest, while looser states are located in the North East, the West Coast, and some of the Mountain States. We calculated state tightness with a composite index, compiling multiple variables. This includes items that reflect the strength of punishments in states, including the legality of corporal punishment in schools, the percentage of students hit/punished in schools, the rate of executions from 1976 to 2011, and the severity of punishment for violating laws, as well as the degree of permissiveness or deviance tolerance in states, which includes the ratio of dry to total counties per state and the legality of same-sex civil unions. The index also captures the strength of institutions that constrain behavior and enforce moral order in states, including state-level religiosity and the percentage of the total state population that is foreign, an indicator of diversity and cosmopolitanism.

Like our international study, our research on the 50 states shows that some striking similarities in why states vary in the strength of their social norms: Tight states have more threatening ecological conditions, including a higher incidence of natural disasters, poorer environmental health, greater disease prevalence, and fewer natural resources. Tight states were also found to have greater perceptions of external threat, reflected in the desire for more national defense spending and greater rates of military recruitment. This may have a historical basis, as states with a large amount of slave-owning families in 1860—those states that were “occupied” by the North and lost the backbone of their slave-based economy following the Civil War—are tighter. In all, we argue that ecological and historically based threats necessitate greater coordinated action to promote collective survival. One might use this construct to predict, for example, that states that increasingly have natural disasters, resource threats, or even terrorism threats might start to become tighter.

This study also helps to explain the vast differences we see in personality across the United States. Tighter states had a higher average of conscientiousness—a personality characteristic associated with lower impulsivity, greater self-control, orderliness, and conformity—relative to looser states. In contrast, looser states had greater average openness—a personality characteristic associated with non-traditional values and beliefs, tolerance toward difference, and cosmopolitanism.  There are many other interesting differences between tight and loose states. Tight states have greater social organization (less instability and greater cohesion), better indicators of self-control (lower alcohol and illicit abuse), and lower rates of homelessness relative to loose states. However, they also exhibited higher incarceration rates, greater discrimination, lower creativity, and lower happiness, as compared to loose states. Tight and loose states each have their own advantages and disadvantages.

As you might expect, the map of state-level tightness-looseness approximates the electoral map of the past few decades, with states voting for conservative, Republican candidates falling on the tighter side and states voting for the more liberal, Democratic candidates falling on the looser side. Yet, conservatism and tightness are distinct, with tightness being a different and broader construct. Conservatism and liberalism are value systems that take the form of individual beliefs, while tightness and looseness describe an external social reality that exists independently of any one individual.  

Our study is not without potential criticisms. First, it is important to note that our results are purely correlational, and accordingly, we can’t infer causation in the data. We have been using some other methods, including laboratory experiments and computer modeling, to strengthen the causal case that tightness is an adaptation to ecological and historical threats. Second, this study was only done in the context of the U.S. which is relatively loose, and in effect, allows for a lot of state variation. It remains to be seen whether other tight countries (e.g., Japan) have as much variation. S. Finally, we focused on the state level, but clearly there is also some interesting within-state variation that could be examined. For example, although Louisiana is a tight state, New Orleans may be a fairly loose city with a lot of behavioral flexibility. Likewise, although California is loose, it has pockets of tight counties.  In our case, we were interested in broad, state level differences rather than specific localities. Other researchers may be interested in other levels of analysis to explore the construct.

In conclusion, E pluribus unum is an accurate descriptor of the United States. Out of many, seemingly disparate variables, it is important to seek a general, unifying principle to explain their concordance. We show that tightness may be one such candidate.