Virtually all agency creative executives and many marketers have preached for decades that advertising works by making emotional connections, not rational appeals. It turns out, they were right, and are even more so over time—at least according to one new study.

Brand Keys, which has been surveying people about brand preference and what drives it for 25 years across more than 4.3 million interviews, has released findings from a meta-analysis of all that data. And it shows that emotional factors bypassed rational ones in a big way over time.

Subscribe to Ad Age now for the latest industry news and analysis.

In 1997, the ratio between rational and emotional considerations in driving brand preference was about 60%-40% in favor of the rational, according to Brand Keys President and Founder Robert Passikoff. Now, the mean across all categories surveyed is closer to 80%-20% in favor of emotional over rational appeals.

That’s a huge swing over a quarter century. It’s been driven, Passikoff said, by a combination of more categories seeing quality parity—i.e. commoditization—and more marketers being swayed by the primacy of emotional appeals and adapting their advertising accordingly.

But the primacy of emotional factors doesn’t mean just having entertaining ads is going to work, he noted. First, people have to be able to link the ad to the brand. Second, all kinds of factors lead to forming emotional attachments, including a broad range of experience and associations with the brand.

“Advertisers tend to make the mistake to think that entertainment is a replacement for emotional engagement,” Passikoff said. “It isn’t.”

Ads that make people feel good about themselves for using a product, for a variety of reasons, can work. For example, aligned with the rise of emotional over rational factors, consumers really do place importance on alignment of a brand with their outlook on social issues, Passikoff said. So the much-ballyhooed "purpose marketing" might actually be paying off. But what drives emotional attachment also can vary by category.

How Brand Keys measures the mix of emotional vs. rational in driving brand choice is complex. But it boils down to asking people about how they rate brand preference overall, and also rating how they see brands in terms of rational factors like product quality, features and price while also asking questions—sometimes less direct—to gauge their emotional attachment to the brand. Correlating people’s rational and emotional evaluations of brands with their overall brand preference helps indicate which factors are most decisive.

The rise of the emotional over rational appeals tracks nicely with how marketers have evolved over the past 25 years.

For example, Procter & Gamble Co. was once legendary for its army of analytical marketers bent on driving home product benefits and other rational appeals in ads. Then, early in the millennium under former global brand officer Jim Stengel, the company began emphasizing more emotional appeals in ads, sending marketers to Cannes in an effort to transform the culture. Rival Unilever and others evolved on a similar timeline, as even the most hardline rational marketers turned to more emotional appeals.

Even so, there remains plenty of room for the rational. P&G, currently on a multi-year streak of beating top-line expectations and broadly gaining market share, evaluates the success of its marketing via what it calls “noticeable superiority,” or how consumers rate brands on performance as well as how attached they are to them emotionally. In announcing its latest quarter of beating Wall Street top-line forecasts with 6% organic growth on Jan. 19, Chief Financial Officer Andre Schulten noted in an earnings call that P&G’s brand portfolio is “75% superior by our assessment” which is “reflected probably in the market share results and trends that we’re seeing.”

RSVP for Ad Age’s Super Bowl event on Feb. 8 at AdAge.com/InDepthSuperBowl.

Brand Keys used a wide array of tracking surveys, which included more than 88,000 in the past year and 4.3 million over the past quarter century, covering consumers ages 16 to 65 from nine U.S. Census regions. Brand Keys said its loyalty assessments correlate with consumer marketplace behavior at above 0.8, where zero is no correlation and 1.0 is complete correlation.

Chief among brands making the right connection, according to Brand Keys, include Discover, which has held the top spot in credit cards for all 25 years of the survey; Avis, a 23-year leader in rental cars; Domino’s, which has been a pizza leader for 18 years; Dunkin’, a leader for 16 years in out-of-home coffee; and AT&T Wireless, a leader for 13 years.