Dr Martina Cossu (University of Amsterdam): 'During the Renaissance period, women used to apply drops of "belladonna" herb to increase pupil dilation and appear more attractive. Almost 400 years later, our study shows that they overlooked the fact that bright eyes with constricted (smaller) pupils appear more attractive than dilated (enlarged) pupils.'

3000 participants

The researchers conducted six experiments testing the effects of pupil size on attractiveness. The pupil is the dark circle in the centre of the eye, and the iris is the coloured ring around it. The researchers showed nearly 3000 participants (of Canada, the US, the UK and the Netherlands) headshots and images of blue or brown eyes from males and females. These images were edited so that one version showed the eyes with constricted pupils and in another version, dilated pupils.

The participants were then asked to evaluate how attractive the faces were. The study found that the faces were judged more attractive with smaller pupils, which show larger irises.

Colour or black and white?

The experiments also tested whether participants found the faces with larger irises more attractive because they were more colourful, or because they made the eyes appear brighter. Results were the same when participants judged black and white images of people with dilated and constricted pupils, proving that the effect is not due to the colour of the iris.

More than 50 years of research

Professor Zachary Estes (Bayes Business School at City, University of London) said: 'For more than 50 years, research has failed to identify whether people appear more attractive with dilated (enlarged) pupils or constricted pupils. Our research reveals that constricted pupils enhance physical attractiveness by making the eyes appear brighter.'

Dr Maria Trupia (postdoctoral scholar from the UCLA Anderson School of Management) added: 'Previous research has shown that physical attractiveness influences a wide range of life outcomes, and scholars have spent decades identifying the characteristics that affect perceived attractiveness. Our research uncovers a novel attribute: pupil size.'

Publication details

‘Beauty is in the iris: Constricted pupils (enlarged irises) enhance attractiveness.’ Martina Cossu (UvA), Maria Giulia Trupia (UCLA, USA) and Zachary Estes (City, University of London, UK). Cognition (volume 250, September 2024). DOI: https://doi.org/10.1016/j.cognition.2024.105842.