New UCL study reveals how your body can predict ad effectiveness — before your brain does.
According to Forbes, the average person now encounters between 4,000 and 10,000 adverts per day, whether scrolling Instagram, riding the Tube, or watching TV. Most will vanish from memory in seconds, but now and then, one sticks: a John Lewis tearjerker, an Aldi punchline, or a jingle that echoes in your head for days.
So, what makes certain ads memorable while others fade?
For decades, marketers have tried to decode this mystery using tools like surveys, focus groups, or click-through rates. But people don’t always know how they feel, and what they say doesn’t always match how they respond.
University College London (UCL) researchers set out to solve a key question: can we measure true advertising engagement better than industry tools?
They compared a new method, physiological synchrony (PS), against 12 existing metrics employing different approaches, from facial coding to emotion sliders.
Unlike traditional tools, PS doesn’t rely on self-reports. It listens to the body.
What Is Physiological Synchrony?
PS happens when multiple people’s bodies respond in similar ways at the same time, like a shared increase in heart rate or skin conductivity. In advertising, this alignment could indicate whether an audience is collectively engaged, even if they are unaware.
In a new study, UCL researchers fitted 93 people with wearable sensors to watch 14 real-world ads from brands like Coca-Cola, Burger King, and Colgate. The sensors tracked electrodermal activity (EDA), which rises when we’re emotionally aroused or paying attention. Afterwards, participants’ memory was tested using quick-response image recall, measuring whether they recognised key scenes from the ads.
The results were striking. Out of more than 20 engagement tools tested (including extra self-report measures), only PS could predict which ads people would remember.
Why It Matters
The advertising industry talks a lot about “engagement”. But what that means, and how to measure it, remains surprisingly vague.
Some companies define engagement as how long someone watches a video. Others rely on eye-tracking, facial coding, or emotion scales. However, as the UCL study showed, these tools often disagree. One metric might label an ad highly engaging; another calls it forgettable.
To make matters worse, when researchers fed the metrics fake, random signals, many still rated them as ‘highly engaging’ – a red flag that some metrics confuse noise for genuine audience response. In contrast, PS stood out. It not only predicted memory recall but also had the lowest false-positive rate of any tool tested.
“This method captures something deeper,” the researchers explained. “It reflects subconscious, collective emotional alignment — not just attention, but resonance.”
Instead of asking individuals what they think, PS measures what a group feels, together.
It’s like an audience gasping at a plot twist or laughing at the same punchline. Those shared, invisible moments of connection might be the most honest signal of when an ad truly works.
A Scalable, Human-Centred Future
What’s especially exciting is how accessible this technology is becoming. The UCL study used unobtrusive wearable sensors, but everyday devices like Apple Watches, Fitbits, and even smartphones already record similar physiological signals. These devices routinely track heart rate and other data that could be harnessed to measure synchrony at scale.
This opens the door to real-time feedback, not just in labs, but across real-world settings. Brands could start testing different ad versions and selecting the ones that spark the strongest physiological resonance.
Synchrony could become a powerful, non-invasive way to understand what truly moves audiences, helping advertisers create campaings that are not just seen, but genuinely felt.
Because PS captures shared, subconscious reactions rather than isolated opinions, it has the potential to help brands create more emotionally intelligent and inclusive advertising.
The Ethics of Listening to the Body
Tracking subconscious reactions raises important ethical questions. Can people give meaningful consent to measuring their emotions if they’re unaware of what’s being tracked? What safeguards are needed to ensure that insights are used to inform, not manipulate?
As biometric tools become more available, these issues will only grow. The researchers stress that transparency and accountability must guide any commercial application of PS. While the technology can offer powerful insights, it must never cross the line into exploitation.
Looking Ahead
This UCL research is part of a broader shift in how we understand and measure engagement, not just in advertising but across media and entertainment.
Future studies are already exploring whether PS can predict brand loyalty, emotional impact, or purchase decisions. If proven effective, PS could be integrated into creative testing tools, helping agencies prioritise campaigns that trigger emotional connection, not just clicks or surface reactions
In the age of AI-generated content, these questions matter even more. Brands are increasingly using AI to generate ads. But do they feel human enough to connect? Early evidence suggests that it is not always the case, and PS could help detect when a message hits the mark or misses by a mile.
Reflection: Engagement, Rewired
By measuring the body’s subconscious, real-time responses – not just what people say, but what they feel – PS gives us a deeper, more accurate understanding of what truly connects.
Finding what resonates is more important than ever in a world overflowing with content. And it turns out that the secret to unforgettable advertising might not be what we think, but what we feel, together.
Cover Image: Wikipedia (Times Square)
