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A video decoding Indian headshakes has gone viral, attracting over a million hits in a week. What does its popularity tell us about the way Indians see themselves?

"A lot of people might find it strange," says Paul Mathew. "But if you are born in India, as you grow up, it becomes a part of your character, your personality, that as you talk you tend to move your head in different ways." Mathew, originally from south India but now working in the film industry in Mumbai, is the writer and director of Indian Headshakes - What Do They Mean? which has garnered more than a million views on YouTube since it was uploaded last week. "If we had known that this video was going to get such awesome viewership we would have shot it better," he says.

The film presents an array of headshakes and shows how subtle variations in velocity, vigour and amplitude of wobble denote different meanings, including: "yes", "no", "maybe", "what's up?" and "carry on". Mathew admits that his headshakes have been somewhat exaggerated for comic effect, but maintains that it's a true picture of a national trait. The response on social media has been broadly positive. "Oh the accuracy! Love it :)" reads one comment on YouTube. Other comments are a little more sceptical, with some saying that Indian headshakes are more prevalent in the south than the north of the country. BBC Monitoring's Vikas Pandey says that most Indians shake their head unconsciously, with many only realising they do it when foreigners ask them if they mean "yes" or "no". He believes the popularity of the video within India is a sign of the country's growing internationalism. "Indians are becoming more self-aware," he says.

But for people with an Indian background living outside the country, the joke might be a bit old. "It's not so much that I'm offended by it - it's just that I expect better," says Niraj Chokshi. Now at the Washington Post, Chokshi has previously written for the Atlantic about humour directed at Indian Americans. He criticises Mathew's film for a lack of subtlety, but he believes it's accurate - and helpful. "I think a lot of racial humour is helpful in that it interprets and it deconstructs cultural norms that people may be afraid or feel too awkward to ask about."

Reporting by William Kremer

Is this just in India? Are there similar head gestures where you are? Tweet us @BBCtrending using #BBCtrending or email us on trending@bbc.co.uk