Robert J. Sampson, chairman of the Department of Sociology, speaks last night on the effects of race and immigration on city crime rates.

In a discussion of his research last night, Sociology Department Chair Robert J. Sampson proposed explanations for what he called the “black-white gap in violence,” arguing that much of such a gap is based on the environment in which an individual is raised rather than on race.

Sampson’s study of the determinants of crime in Chicago and Boston, which he presented at the Kennedy School of Government’s Rappaport Institute for Greater Boston, concluded that, even though black youths’ rates of violent acts are, on average, about 85 percent higher than those of whites and Latinos, environmental factors account for more than 60 percent of this gap.

Sampson, who is also Ford Professor of Social Sciences, said these environmental factors are the marital status of the youths’ parents, their immigrant generation, and the socioeconomic makeup of their neighborhood.

Over the years, explanations proposed for the black-white gap have ranged from socioeconomic status and prevalence of single-mother households to varying levels of impulsiveness in different racial groups.

Sampson’s findings confound some stereotypes about race and violence.

“In our data, immigration is associated with lower violence, not higher,” said Sampson.

He jokingly proposed an “America effect” that raised crime rates, commenting on the fact that “the longer the amount of time spent in the United States, the higher the rate of violence.”

Sampson’s study found that people’s perceptions of disorder in their neighborhoods were affected by the prevalence of minorities.

“There’s a cultural stereotype [not only among whites] that violence and disorder is associated with minority groups,” said Sampson. He added that this perception bias complicates the process of addressing real differences in rates of violence.

“People are acting on beliefs that reinforce the patterns that exist,” he said.

His data for Chicago also showed that Latinos committed violent acts at a rate 10 percent lower than whites. However, when their surroundings were taken into account, the gap disappeared.

The discussion last night, attended by about 60 people, was not limited to purely academic concerns. J. Larry Mayes, the Chief of Human Services for the City of Boston, weighed in, with a practical perspective, on working with immigrant communities in Boston.

Mayes anecdotally addressed the problems some immigrants from the West African island nation of Cape Verde encounter when they arrive in the Boston area. He suggested that cultural problems of integration contributed to recent violence in Boston’s Cape Verdean community.

“They didn’t have the filters to deal with the advent of pop culture, especially thug culture,” Mayes said.

Sampson said he is cautiously optimistic about trends of lowered violent crimes in recent years. Commenting on the broad-based international decline in crime rates, he said, “there could be some sort of cultural shift going on in advanced industrialized countries.”

Audience members responded favorably to the forum.

“It’s nice that community leaders get to interact and have an exchange of ideas with researchers,” said Reanne Frank, a postdoctoral student at the Harvard School of Public Health.