In a 2018 survey of 803 Internet users by UK-based digital marketers Varn, 57.5% of respondents said that they were unable to recognize Google Ads in pages of search returns.

Findings:

• All respondents:
  • 57.5% said they cannot recognize Google Ads.
  • 34.8% said they can recognize them and don't click on them.
  • 7.7% said they can recognize them and do click on them.
• Respondents by sex:
  • Unable to recognize: 48.2% male, 51.8% female
  • Recognize and don't click: 50.0% male, 50.0% female
  • Recognize and do click: 68.7% male, 31.3% female
• Respondents by age:
  • Unable to recognize: 50.2% of those aged 18-34, 61.6% of those aged 35+
  • Recognize and don't click: 41.4% of those aged 18-34, and 31.2% of those aged 35+
  • Recognize and do click: 9.2% of those aged 18-44, 6% of those aged 45+

Researchers' conclusions:

• Most people don't know the difference between Google Ads and organic listings in SERPs.
• Across demographic groups, 34.8% of people who say they are aware of the difference tend not to click on Google Ads. So improve organic search rankings wherever possible.
• 35+ is best target age group for Google Ads
• Ads targeting younger people may need to be more age-specific.

FYI: Varn has done this type of survey 5 times since February 2016. And the % of respondents who say they're unable to recognize Google Ads has steadily increased.

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Comments:

• Sample size is pretty small, and probably drawn from UK only. But results are consistent over 5 replications, and grossly similar to those of studies done by others.
• Since 68.7% of people who recognize and click on Google Ads are men, Google Ads look like a good channel for marketing to men. Because we tend to click on them regardless of whether or not we recognize them as ads. (What could account for that sex difference? Is it because women are more attracted to ads with images, as other research has shown, while Google Ads in SERPs are text ads? If you have another theory, please let me know.)
• Response of over-35s to Google Ads will likely change somehow as under-35s age. Need to keep revisiting this kind of research.
• If you've ever tried to write age-specific ads for young people using only 140 characters of text and no visuals, you'll have an appreciation of how difficult that can be.