Biometrics and Experimental Consumer Psychology

Ben Ambridge

At Endless Gain, our state-of-the-art biometrics setup combines five technologies: Eye Tracking, to tell you which parts of your site customers are looking at and when; Facial-Expression Recognition, to tell you how they’re feeling when they’re doing so; Galvanic Skin Response, to measure the strength of these emotions; EEG to measure their engagement with your site; and Pupil Dilation to measure their arousal.

We are the pioneers of using biometrics to understand consumer behaviour, and then to optimise consumer behaviour. Biometrics on their own are very useful, but the real gains come when they are paired with psychology.

For example, eye-tracking technology can tell you where your customers are looking; but psychology can tell you where you want them to be looking, and how best to achieve this.

This special five-part series, demonstrates the link between the biometric techniques that we use at Endless Gain, and cutting edge theories and findings from experimental consumer psychology research using (1) Eye Tracking, (2) Facial Expression Recognition, (3) Galvanic Skin Response, (4) EEG and (5) Pupil Dilation.

What Is Eye Tracking?

Eye tracking technology monitors customers’ eye movements as they browse a website, and – at a basic level – is used to answer questions like whether customers notice a particular product or advert, and which parts of the site they skim briefly, and which they pay more attention to.

But when paired with the right experiment or test, it can tell us so much more.

Some of the earliest studies (summarised in a 2012 review paper by Hilke Plassman and colleagues)1 used eye-tracking to identify features that automatically command our attention. The big four are faces, text, novelty and one’s own name. And when I say “automatically”, I mean it: If I show you an otherwise-fairly-plain website with a picture of a face, you’ll look at the face, even if you’re trying not to.

The same goes for your own name (which is presumably why sites such as eBay and Amazon display your name at the top whenever you’re logged in).

Where do people look?

Another batch of early studies investigated not what people look at, but where they look. A famous study from the 1970s by Richard Nisbett and Timothy Wilson2 found that, when five identical stockings were displayed horizontally (obviously in real life, not on the internet), customers were most likely to choose the pair on the right.

That said, an eye tracking study published by Eleana Reutskaja3 in the American Economic Review  found that the centre of the screen is also special, with customers 60% more likely to choose a product displayed centrally than one shown elsewhere.

Two further studies drilled down into the cause of this “centre stage effect”. Although centrally-presented items do receive more attention when the page is first displayed, what actually predicts purchasing is increased looking to the centre just before the decision is made, as reported in a 2012 study by Selin Atalay4.

Interestingly, a 2009 study by Ana Valenzuela and colleagues found that customers are savvy to the centre-stage effect5, and so expect the item in the centre to be the most popular, and – therefore – probably the best choice for them. Either way, if your key product or call-to-action button is in the bottom left-hand corner, you’ve got problems.

Eye Movements matter

But it’s not just about where customers end up looking; eye movements are crucial too. A 2014 study by Anneleen Van Kerckhove and colleagues6 found that customers who looked up were more likely to select a more desirable product than a more realistic option (e.g., iPhone X vs a cheaper Android phone with similar spec), while customers who looked down showed the opposite pattern.

Even more intriguingly, a 2016 study by Hao Shen at Hong Kong University7 found that if participants repeatedly perform the same eye movement – e.g., left to right – and then do so again when asked to evaluate a product, they give it higher ratings. What seems to be happening is that participants get better at making the eye-movement with practice, and incorrectly interpret this increased “fluency” as a liking for the product.

Similarly, because we perceive time as flowing from left-to-right, a 2013 study by Boyoun Chae found that products are rated more favourably when positioned in that order8 (e.g., an antique lamp on the left, a modern lamp on the right) than vice versa (though watch out: if your customers speak a language that is written from right to left – such as Arabic or Hebrew – it’s the opposite).

How long do people look?

But when it comes to looking durations, more isn’t always better. Yes, in general, customers do tend to look for longer at the item that they end up purchasing. But increased looking times can also be a sign that something doesn’t quite add up.

For example, an eye tracking study (conducted just down the road from our office), by Andrew Stewart at the University of Manchester9, found that customers were happy with the idea of Polaroid-branded audio tape (since the company makes cameras and film), but not Polaroid-branded serving dishes.

Finally, it’s important to remember that, while all of these findings are from rigorous peer-reviewed academic studies, every product and every website is different. Therefore, extensive testing is needed to figure out how best to apply them to your own site.

And at Endless Gain, we are the world leaders in teaming up biometrics – not just eyetracking, but EEG, pupil dilation, skin conductance and facial expression recognition too – with theory and findings from cutting edge Psychology.


[1] Plassmann, H., Ramsøy, T. Z., & Milosavljevic, M. (2012). Branding the brain: A critical review and outlook. Journal of Consumer Psychology, 22(1), 18-36.

[2] Nisbett, R. E., & Wilson, T. D. (1977). Telling more than we can know: Verbal reports on mental processes. Psychological Review, 84(3), 231.

[3] Reutskaja, E., Nagel, R., Camerer, C. F., & Rangel, A. (2011). Search dynamics in consumer choice under time pressure: An eye-tracking study. American Economic Review, 101(2), 900-926.

[4] Atalay, A. S., Bodur, H. O., & Rasolofoarison, D. (2012). Shining in the center: Central gaze cascade effect on product choice. Journal of Consumer Research, 39(4), 848-866.

[5] Valenzuela, A., & Raghubir, P. (2009). Position-based beliefs: The center-stage effect. Journal of Consumer Psychology, 19(2), 185-196.

[6] Van Kerckhove, A., Geuens, M., & Vermeir, I. (2014). The floor is nearer than the sky: How looking up or down affects construal level. Journal of Consumer Research, 41(6), 1358-1371.

[7] Shen, H., & Rao, A. (2016). Looks good to me: How eye movements influence product evaluation. Journal of Consumer Psychology, 26(3), 435-440.

[8] Chae, B., & Hoegg, J. (2013). The future looks “right”: Effects of the horizontal location of advertising images on product attitude. Journal of Consumer Research, 40(2), 223-238.

[9] Stewart, A. J., Pickering, M. J., & Sturt, P. (2004). Using eye movements during reading as an implicit measure of the acceptability of brand extensions. Applied Cognitive Psychology, 18(6), 697-709.