New research from On Device has revealed that ad recall, which is still widely used as the basis for brand lift measurement, produces inaccurate results in 8 out of 10 cases.
The findings highlight the urgent need for advertisers, agencies, and adtechs to move beyond outdated memory-based methods and adopt passive exposure measurement, delivering accurate, trusted insights to guide meaningful decisions.
Ad recall research
Analysing brand lift studies for more than 2,000 digital campaigns, On Device compared ad recall responses against real, passively measured, ad exposure.
The study found that ad recall consistently misattributes who had or hadn’t seen an ad. This produced both false positives of people recalling ads they never saw, and false negatives of people forgetting ads they did see.
This contamination of exposed and control groups inflated uplift figures, making ad recall an unreliable foundation for the measurement of advertising effectiveness and subsequent media planning decisions.
The analysis also uncovered the impact of customer selection bias. Further in-depth analysis of 15 passive measurement studies selected at random found ad recall for existing customers was on average 3.1 times higher than for non-customers, despite both groups having comparable exposure to the campaigns.
In practice, this means that in an ad recall exposed group, seven out of ten people are likely to be existing customers. Rather than measuring true brand lift, ad recall is measuring pre-existing brand relationships and inflating campaign results.
With UK digital ad spend expected to grow ~10% annually to reach £45 billion by 2026, the stakes for measurement accuracy are only rising.
At the same time, Q1 2025 saw the first quarterly decline in UK marketing budgets in four years (net –4.8%), meaning every pound wasted matters more than ever.
“Memory is messy and error-prone”, said Alan Bantick, Head of Research at On Device. “People recall ads they didn’t see, forget ads they did, and sometimes confuse one brand for another.
“When your exposed and control groups are built on these shaky foundations, your measurement is fundamentally flawed”.
“Our analysis proves that ad recall is not fit for purpose as a proxy for exposure.
“If advertisers want measurement they can trust to guide budgets, passive methodologies are by far the most reliable solution.”
While ad recall is often chosen because it is easier and cheaper to run, the consequences are serious. Misleading results can distort future planning, erode advertiser trust, and waste valuable marketing spend.
On the flip side, accurate, passive measurement not only provides cleaner data but also underpins long-term growth by giving brands clarity on what truly drives performance, so the effectiveness of future media plans can be enhanced.
For deeper insights and recommendations on improving brand lift measurement, download the full paper – Brand Lift’s Biggest Mistake: Why ad recall Falls Short from on-device.com.