So advertising works. Even on me.

I sat down with Sensum to see just how much the inconceivable friendship between a hare and a bear would really make me want to buy an alarm clock.

Sensum’s tech combines the biological response to a given ad, using a sensor to detect changes in skin moisture, plus the Sensum app, where the viewer lodges their gut response to what they’re seeing.

Belfast-based co-founders Gawain Morrison and Shane McCourt started out making horror films where the narrative was directed by the audience’s reaction. They then developed the Sensum platform, which visually displays the participants’ emotional responses, to measure bikers’ heart rates during the NW200 motorcycle race for BBC Northern Ireland.

The pair showed me the John Lewis Hare and Bear Christmas ad on a tablet and then on a big screen to see if there was a difference between my responses when viewing ads on different devices. John Lewis didnt use Sensum, but what if they had?

Thankfully for advertising agencies everywhere, I was aroused and pleased (in ad speak terms) for much of the ad on both the large and small screens – with peaks during the money shots – where the rabbit leaves the bear a gift and when the bear emerges to meet its friend for their first Christmas together.

I was even surprised to see my internal feelings for the John Lewis register when the branding came on screen. I guess I like John Lewis, they’re an employee-owned partnership, so I like their ethics, but would I have been so responsive to another brand?

So which platform worked better? With headphones on viewing on the tablet, I was actually more immersed and engaged, according to the stats, particularly in the biological test. This means the message was actually more likely to be committed to memory, showing mobile may be the right avenue for brand campaign managers keen to go beyond the banner.

The platform, developed with psychologists and scientists, has just come out of beta and the company is now touring around the world, debuting it at conferences like SXSW in the US. They are keen to show Sensums potential as a real-time, reactive solution for mobile marketing –  you can take it out of the lab and into the home, the cinema or on the bus to see how effective ads are in different settings.

While Morrison said that brands are curious – how do we get to emotions and measure it? – the practice is not without its critics. Isn’t this all a bit like cheating? And what does this mean for creativity in marketing, and other areas of production, if you can measure emotions and tweak your narrative accordingly? “There are those that don’t want to embrace new technology, there are those that are brilliant at what they do but there are also those that will find value in these new tools to improve what they do,” Morrison said.

He points to an art dealer featured in a recent BBC film who was put into an MRI scanner and asked to judge famous pieces. Because of the cultural context, his understanding of the art world, he was keen to say pieces were good, even when his brain said otherwise. So how can you really tell whether an audience is being truthful without finding out more than just what they say?

“Looking at a campaign like the Lynx Effect, how might that have worked had they used focus groups?” he said. “Would 18 to 24-year-old boys have admitted in a group setting that the ad would speak to them? What if an attractive woman, or a blokey bloke, had been directing the questions?” Whatever process they used, the campaign provided a 3.8 per cent uplift in sales, Morrison says. And no doubt Sensum would have been able to reveal the inner feelings of its target audience.

But where is all this data mining going to lead? Morrison pointed to companies like Nike, Jawbone and Fitbit, who already bringing the personal data revolution to life within their wearable fitness solutions. But similar platforms have recently been accused of selling their data to insurance companies, presumably for use when selling policies to consumers. What will solutions like this mean for data protection and potential litigation? Who owns it?

Sensum is now part of the Neuromarketing Science and Business Association, a growing area of the advertising industry creating solutions that use peoples explicit and implicit emotions to improve what they do. The organisation has a lengthy code of ethics, but like other areas of marketing, legislators may start having to play catch up.