LOS ANGELES (CBSLA.com) — It turns out behind every conservative Republican man is a sister, according to researchers.

Researchers at Loyola Marymount University and Stanford Graduate School of Business released a study Tuesday that found men who were raised with female siblings tend to be conservative in their views of gender throughout their lives, and more likely to vote Republican when they’re young than their male peers.

The report titled “Childhood Socialization and Political Attitudes: Evidence from a Natural Experiment” found boys with only sisters were 13.5 percent more conservative in their views of women’s roles than boys with all brothers.

Researchers Andrew Healy and Neil Malhotra suggest one reason for the trend may be those future conservative voters are much less likely to share household chores with their sisters, an avoidance of housework that continues into adulthood.

Watching their sisters do the chores “teaches boys that housework is simply women’s work”, according to Healy and Malhotra, a conclusion the researchers say leads to a traditional view of gender roles – a position linked to a predilection for Republican politics.

When the boys with female siblings were seniors in high school, they were nearly 15 percent more likely to identify as Republicans, but as they grew into middle age, that effect diminished sharply. On the other hand, having sisters instead of brothers has no significant effect on girls, Healy and Malhotra found.

Other researchers have found that people with traditional views on gender roles are 25 percent more politically conservative.

“These effects were surprising to us,” Healy said. “We might expect that boys would learn to support gender equity through interactions with their sisters. However, the data suggest that other forces are more important in driving men’s political attitudes, including whether the family assigned chores, such as dishwashing, according to traditional gender roles.”

The researchers base their conclusions on an analysis of data gathered for two earlier studies: the University of Michigan Political Socialization Panel (PSP) and the National Longitudinal Survey of Youth (NLSY) young-adult sample.

The PSP study began in 1965 as a national sample of 1,669 high school students from 97 public and private schools, and their parents. Subsequent surveys of the same individuals were conducted in 1973, 1982, and 1997; by the time of the last survey, the former students were about 50 years old.

The NLSY survey, which was conducted by the Bureau of Labor Statistics, included interviews with children as young as 10. Over the years, questions about political views were added to the NLSY.

When that data was correlated with the PSP, Healy and Malhotra said they concluded “the gender stereotyping of the childhood environment thus may help to explain the effects that sisters have on male political attitudes.”

Click here to read the entire study of “Childhood Socialization and Political Attitudes: Evidence from a Natural Experiment”.