In 2002, Braun, Ellis and Loftus ran an experiment where they implanted false memories of advertisements people had never actually seen. It’s a vivid demonstration of how malleable memory can be—not just for advertising, but in general.
This is a problem for measuring advertising effectiveness. There are several methods for doing this: surveys before and after a campaign, showing participants clips of TV ads and asking if they recognise them. These methods have been used for decades, but they all rely on the accuracy of participants’ memories. If memories can be reshaped or simply wrong, the recall of an advert may not be the best starting point.
One method that helps get around this problem is Google Analytics. It’s not as in-depth as an expensive ad tracking study, but it’s cheap and measures actual actions rather than remembered impressions. You can track any campaign (offline or online) that has an online destination or goal. It’s particularly useful if you’re interested in conversions directly linked to a campaign, rather than things like raising brand awareness.
There’s a solid guide on using Google Analytics for ad tracking if you want to try it yourself.
Of course, this only tells you who clicked—not whether the ad actually changed how they think about your brand. Maybe that’s a question surveys were always bound to struggle with.