"Someone's not telling the truth," laughs internet stats guru Bill Tancer as he tells TechRadar of his latest stunt at conferences – asking for a show of hands on who accesses adult sites.

Tancer, the author of CLICK: What We Do Online and Why It Matters and General Manager of Global Research for web stats company Hitwise, certainly knows what he's talking about.

"I ask by a show of hands how many people access adult entertainment and sites," he says when TechRadar asks him about the disparity between what we admit to publicly and what we actually do on the internet.

"Out of thousands of people I've only ever got one person raise his hand and that was the sound guy at one of conferences I was doing.

"And then you go online and look at the percentage of the online population that accesses adult entertainment sites - ­here in the UK I think it's 7.7 per cent and in the US it's about 11 per cent, so clearly someone's lying."

Cognitive dissonance

It's not all about peope's embarrassment over their porn habits however, with Tancer admitting that 'cognitive dissonance' or saying one thing while doing another is a common trait.

"People want to appear in the best possible light," he adds. "They don't want to appear unsavoury in an audience of other people so they might change their answer.

"Adult sites are an extreme example, but it can come into play with much smaller things.

"Sometimes it's a matter of recall, but often people just want to answer in a way that makes them look intelligent."