Most marketing copy is bad in ways that are actually research-documented. Over the last twenty years, academic psychology and consumer-behavior research have produced a stack of findings about which words work and why. Most marketers haven't read this research. Some of it is genuinely counterintuitive.
I want to walk through five findings that, taken together, should change how you write headlines, body copy, social posts, and emails. Each is grounded in a specific peer-reviewed paper.
1. Present Tense Beats Past Tense
In 2023, Grant Packard, Jonah Berger, and Reihane Boghrati published a paper in the Journal of Consumer Psychology called "How Verb Tense Shapes Persuasion." They analyzed thousands of product reviews and found a consistent pattern: reviews written in present tense were significantly more persuasive than equivalent reviews in past tense.
"This coffee is amazing" outperforms "This coffee was amazing."
The mechanism, per the authors: present tense signals current certainty. Past tense signals historical experience. The reader's brain treats current certainty as a stronger evidentiary signal than historical experience. The grammatical choice tilts the entire credibility weighting.
The operational implication for marketing: when quoting testimonials, prefer the ones written in present tense. When writing your own product copy, prefer "Domino's makes the most consistent delivery pizza in fast food" over "Domino's has made consistently good pizza for forty years." The first is stronger, even though the second contains more information.
Jonah Berger's book Magic Words covers this finding and a half-dozen related ones at length. It's worth reading the whole book if this kind of micro-linguistic research interests you.
2. Size Captures Attention
Rik Pieters and Michel Wedel published a 2004 paper in the Journal of Marketing on text-size effects in print advertising. The finding: ads where some words were noticeably larger than others captured more attention than ads with uniform text size — and the effect was strongest when the emotional words were the larger ones.
Your brain evolved to equate size with importance, and possibly with threat. Uniform text gives the brain nothing to lock onto. Variable size forces the eye to attend to the larger elements and gives those elements disproportionate emotional weight.
This isn't permission to crank up every font in your copy. It's a reason to be deliberate about which words you size up. Pick the most emotionally loaded word in any headline. Make that the biggest. Let everything else recede.
If you've ever wondered why old Volkswagen ads from the Doyle Dane Bernbach era were so effective — "Lemon." "Think small." — it's largely this. The DDB creative team intuited Pieters and Wedel's finding decades before the research was formalized. One huge, emotional word. Then everything else.
3. Make It Familiar (MAYA Principle)
In 1951, the industrial designer Raymond Loewy — the man who designed the Studebaker Avanti, the Shell logo, the Coca-Cola fountain, Air Force One's livery — published an autobiography called Never Leave Well Enough Alone. In it he laid out a design principle he called MAYA: Most Advanced Yet Acceptable.
Loewy's argument was that humans are pulled simultaneously by two opposing forces: neophilia (a curiosity about the new) and neophobia (a fear of the new). The successful product, ad, or brand sits exactly at the threshold where these forces balance. Familiar enough to feel safe. Novel enough to feel exciting.
The behavioral economics underneath this is Robert Zajonc's 1968 research on the Mere Exposure Effect — the well-replicated finding that humans like things more the more we see them. New things, by definition, lack exposure. So they need to be presented in a familiar frame to feel acceptable.
Derek Thompson's book Hit Makers extends this argument across pop music, film, and consumer products. Every big hit, Thompson argues, is a familiar surprise — recognizable enough to feel safe, novel enough to feel interesting.
The operational implication: when you're selling something genuinely new, don't lean into its novelty. Lean into a familiar metaphor for it. Steve Jobs introduced the iPhone in 2007 not as "a revolutionary new computing platform" but as "an iPod, a phone, and an Internet communicator" — three things the audience already knew, recombined. That's MAYA.
4. Certain Language Beats Hedged Language
In a 2021 paper in the Journal of Interactive Marketing titled "Certainty in Language Increases Consumer Engagement on Social Media," researchers Pezzuti, Leonhardt, and Warren analyzed social-media engagement across thousands of brand posts. The finding: posts using certain language ("always," "forever," "everything," "completely") got significantly more likes, shares, and retweets than posts using hedged language ("might," "could," "may," "sometimes").
The mechanism is that certain language signals brand power. A brand confident enough to make absolute claims registers, in the reader's brain, as a brand worth engaging with. Hedging registers as weakness.
The implication for copy is uncomfortable for anyone with a legal background. "Customers love our product" beats "Customers often report satisfaction with our product." Of course, you can't make claims you can't substantiate. But within the range of substantiable claims, the more certain framing wins.
This is, incidentally, why "A diamond is forever" is one of the most successful ad campaigns in history. De Beers's slogan from 1947, written by copywriter Frances Gerety, contains no qualifier. The diamond is forever. Not "lasts a long time." Not "should outlast you." Forever. The certainty is the asset.
5. Indirect Claims Outperform Direct Claims
In 2013, Edward McQuarrie and Barbara Phillips published a paper in the Journal of Advertising called "Indirect Persuasion in Advertising." They found, across multiple experiments, that metaphorical or implied claims outperformed direct claims for memorability and persuasion — particularly in image-heavy media.
This contradicts a lot of marketing 101 advice, which leans toward "be clear, be direct, tell them exactly what you sell." McQuarrie and Phillips's research suggests that's wrong — at least for emotional engagement.
The mechanism is that indirect claims invite the reader to complete the meaning themselves. The reader's brain does the inferential work, and the brain values conclusions it generated itself more highly than conclusions handed to it.
This is the territory George Lakoff covered in his 1980 book Metaphors We Live By — the foundational text on how metaphorical framing shapes thinking. It's also why slogans like "Just Do It," "Think Different," "The Ultimate Driving Machine," and "You're not you when you're hungry" outperform their literal alternatives.
Snickers's "You're not you when you're hungry" is dramatically more effective than "Snickers is filling." The first invites you to fill in your own experience of being hungry. The second just tells you what the product does.
How To Apply All Five
These five findings stack. You can use them simultaneously in a single piece of copy.
A bad ad headline might say:
"Our coffee is good and we hope you'll consider buying some."
A version that applies all five findings might say:
"Coffee, perfected. Forever." — present tense, three emotional words sized for impact, MAYA-acceptable, certainty language, indirect claim.
That's a difference of about thirty words. Across a thousand ads over five years, those word-level decisions compound into substantially different conversion rates.
If you want the academic reading list: Berger's Magic Words, Cialdini's Pre-Suasion, the Heath brothers' Made to Stick, Phil Barden's Decoded, and Derek Thompson's Hit Makers. Five books, and you'll understand more about why some copy works and other copy doesn't than 95% of working marketers do.