Hundreds of gay rights supporters in conservative and mainly Catholic Croatia staged a protest on the eve of a constitutional referendum that could outlaw same-sex marriage.

London - Campaigners for same-sex marriage have often come up against opposition from heterosexual men.

But a study from the US has suggested a novel method of persuading them to soften their stance on the divisive issue: get them to watch dirty videos.

The new academic analysis suggests that the more that straight men watch pornography, the more they warm to the idea that two people of the same sex could be married.

Paul Wright, assistant professor of communications at Indiana University and author of the study, said the effect was particularly marked in men who were less-well educated.

He said the change in attitude could be because pornography opens their mind to accepting non-traditional sexual situations – like those involving participants of the same sex.

“Our study suggests that the more heterosexual men, especially less educated heterosexual men, watch pornography, the more supportive they become of same-sex marriage,” he told the Washington Examiner.

“Pornography adopts an individualistic, non-judgemental stance on all kinds of non-traditional sexual behaviours and same-sex marriage attitudes are strongly linked to attitudes about same-sex sex.

“If people think individuals should be able to decide for themselves whether to have same-sex sex, they will also think that individuals should be able to decide for themselves whether to get married to a partner of the same sex.”

The results of the study, published in the journal Communication Research, could be interpreted as suggesting that backers of same-sex marriage should encourage men to watch more porn.

Wright said: “Since a portion of individuals’ sexual attitudes come from the media they consume, it makes sense that pornography viewers would have more positive attitudes towards same-sex marriage.”

If figures on internet usage are correct, it is likely that support for same-sex marriage will be fairly strong worldwide – researchers last year revealed a staggering 30 percent of all online traffic is pornography.

The biggest porn site on the web – Xvideos – receives 4.4 billion page views and 350 million unique visits a month, according to figures revealed last year.

The only sites that surpass this in size are Google and Facebook, according to an investigation carried out by ExtremeTech.

The report uncovered the viewing figures for Xvideos from Google’s DoubleClick Ad Planner, which uses cookies to gather information about users.

It then used these figures – and actual data from the third-biggest porn site, YouPorn – to extrapolate how much data is being transferred out of the site’s servers.

It based the first calculation on the average length of time spent on Xvideos, which is 15 minutes, and assumed a low-resolution video was being streamed.

From this it estimated that around 29 petabytes of pornography is being transferred a month, or 50 gigabytes a second.

However, it upped this estimate to 35 to 40PB a month after learning that YouPorn hosts more than 100TB of porn, gets 100 million page views and transfers 950 terabytes a day.

For the latest study, funded by the National Science Foundation, Wright and study co-author Ashley Randall, of the University of Arizona, looked at data from studies of 500 heterosexual men over the past five years.

“Pornography consumption did predict over time increases in support for same-sex marriage,” Wright and Randall wrote. - Daily Mail