How “Social Penumbras” Explain Shifts in Attitudes Toward Different Social Groups

In America’s culture war surrounding same sex marriage, Republican Senator Rob Portman was an active warrior: in 1996 he cosponsored the Defense of Marriage Act, defining marriage as one man and one woman. Three years later he voted for a measure prohibiting same-sex couples from adopting children, and in 2011 Portman’s “openly hostile” record on gay rights led to a mass protest of students at the University of Michigan against his selection as speaker at the graduation ceremony. In response, his spokesman said that “Rob believes marriage is a sacred bond between one man and one woman.”

But two years later, something happened: “I’m announcing today a change of heart on [gay marriage] … My son came to Jane, my wife, and I, told us that he was gay, and that it was not a choice, and that it’s just part of who he is … I’ve come to the conclusion that … [marriage] is something that we should allow people to do … and to have the joy and stability of marriage that I’ve had for over 26 years.” Portman also mentioned his consultation with former Vice President Dick Cheney, whose own daughter’s coming out compelled him to re-think his position and, with time, change his view.

The examples of Portman and Cheney underline the tight link between personal contacts and political views. It also highlights the divergent experiences of different social groups fighting for political recognition and social change. In the past two decades, gay rights have undergone a major transformation in the country, with many states, and later the Supreme Court, recognizing same-sex marriage and with a large share of Americans expressing support for this change. Yet over the same period, despite ongoing calls by activists and politicians for changes to the U.S. immigration system—in particular, granting more immigration visas and providing undocumented immigrants a path to citizenship—strikingly little movement has been registered on these matters.

Why has there been so much progress on gay rights while those of other marginalized groups, such as immigrants, have stagnated?

The contrasting experience of these two hitherto socially discriminated groups—gay people and immigrants—raises a key question: Why has there been so much progress on gay rights while those of other marginalized groups, such as immigrants, have stagnated? Earlier research on variation in the political influence of social groups focused either on differences in groups’ resources or on features that affect their ability to overcome the collective action problem. The political influence of a group is typically explained in terms of its size, geographic concentration, or the intensity and commonality of interests among group members.

However, those might not be the most important factors determining groups’ influence and political sway. In a recent paper we published in the Proceedings of the National Academy of Sciences, we introduce another dimension, the penumbra, defined as the set of individuals in the population who are personally familiar with someone in that group. 

Distinct from the concept of an individual’s social network (which refers to the contacts and relationships of a certain individual), the penumbra refers to the circle of close contacts and acquaintances of a given social group. Using original longitudinal data, the article provides a systematic study of various groups’ penumbras, focusing on politically relevant characteristics of the penumbras (e.g., size, geographic concentration, sociodemographics).

The different sizes and characteristics of these penumbras give insights into the difference in these groups’ political clout.

Two social groups of similarly modest size can have penumbras that vary in crucial ways: a group’s penumbra can be large in size or small, it can be geographically concentrated or dispersed, and it can be composed of mostly rich or poor people. Our research offers a first systematic analysis of this concept as well as insight on its potential political significance. In particular, we provide systematic evidence that changes in individuals’ penumbra status can help explain shifts in their political attitudes.

To get a sense of this, consider three groups from our survey: the penumbra of gay people, the penumbra of Muslims, and the penumbra of women who have had an abortion in the past five years. These three groups are roughly the same size (3.6 percent, 2.4 percent, and 2.0 percent of the U.S. adult population, respectively) but differ widely in the size of their respective penumbras: according to our survey, 74 percent of American adults know at least one gay person, 30 percent know a Muslim, and only 10 percent say they know a woman who has had an abortion the past five years. 

Groups asked about in our survey in increasing order of size. For each group, the area of the yellow circle indicates its size, and the concentric circles show its estimated penumbra: the percentage of survey respondents who report knowing at least one family member, close friend, or other acquaintance in the group. The light gray concentric circle denotes the rest of the US population that is not in the group’s penumbra. Source: PNAS.

The different sizes and characteristics of these penumbras give insights into the difference in these groups’ political clout, as well as aspects of communication and secret keeping—we expect that many people do not realize that one or more of their close friends or relatives have had an abortion. In contrast, the relatively low Muslim penumbra can be explained by the fact that Muslims tend to cluster socially in geographically condense areas. The large gay penumbra is a relatively recent phenomenon: surveys in the 1990s and early 2000s found far fewer people reporting that they knew any gay people.

The study of penumbras is also an example how we can go beyond the traditional atomistic approach to survey research, which tends to focus on attributes of individuals rather than on their social structure. Consider political polls surveying respondents about their voting intentions. Rather than just ask survey participants who they plan to vote for in an upcoming election, researchers can also inquire how they think their relatives, friends, and neighbors might vote. Similarly, in studying the spread of COVID-19, asking about social distancing behavior in one’s social circle rather than just about actions of the respondent herself may be more instructive of the pandemic’s risk of spread in different areas. By turning our attention to the characteristics of the social circles surrounding respondents, we could better incorporate social structure as a factor that explains and predicts individual attitudes and behavior.

Yet doing so requires not only a change in researchers’ approach for data collection, it also requires overcoming some statistical challenges. One key challenge is the small proportion of people who are expected to enter a penumbra in any given year. The gay penumbra, for example, grew from about 25 percent to 75 percent of the population during the past twenty-five years, an increase of about 2 percentage points a year. This rapid growth partly reflects the circular process whereby with evolving social norms, gay and lesbians felt increasingly comfortable revealing themselves as such, in turn increasing the size of the gay penumbra and thus contributing to further change in social norms.

Examining the contacts that group members have with out-group members—how prevalent, how geographically dispersed, how socially homogenous—may offer new insight on the clout and influence of various groups in society.

But even when dealing with such a sizable and growing penumbra, it’s challenging to capture attitudinal change due to penumbra membership. Consider a study such as ours, which compared people who entered the penumbra (i.e., those who met, befriended, or otherwise became acquaintances of a member of these groups) to those who remained outside the penumbra (those who still don’t personally know anyone belonging to these groups) during a one-year period. In a survey of 2000 people, we might expect 40 people to enter a given penumbra, and this is a small sample from which to draw conclusions. While in the penumbras we studied, approximately 10 percent of respondents entered in a one-year time frame, the sample size challenge remains in any study of shifting public opinion in this era of political polarization. We study people who change their views, but they represent a small subset of the population: most people don’t change their minds very often.

The example of Senator Portman’s sudden U-turn on same-sex marriage is a perfect illustration of the intergroup contact theory from social psychology: the idea that personal interactions can, under certain conditions, reduce prejudice between majority and minority group members. Our work suggests that there’s more to gain from this theory by shifting our focus from the individual to the group. Examining the contacts that group members have with out-group members—how prevalent, how geographically dispersed, how socially homogenous—may offer new insight on the clout and influence of various groups in society. With the growing availability of new data sources that allows researchers to track and quantify such contacts, we believe a group-based focus holds great promise for social science research. And beyond the implications for research, our findings also give us hope that significant progress for the representation of marginalized groups is possible through growth of social penumbras.