Emotional ads win for restaurants, rational ads win for dentists.

A dentist and a restaurant owner can both buy a Facebook ad this afternoon, and the temptation is to write the same kind of copy for both: a warm photo, a friendly line, maybe a discount. But the research on advertising appeals says that's backwards for one of them, and the gap isn't small.

Picture the dentist's ad next to the restaurant's. The restaurant shows a plate of food, steam still rising, a couple laughing over wine. The dentist's ad, if it copies that playbook, shows a smiling patient in a chair with soft lighting and a line about "a brighter you." One of these is doing its job. The other is borrowing a tone that doesn't fit what's actually being sold.

Why the dentist and the restaurant need different ads.

A study by Hongxia Zhang, Jin Sun, and Fang Liu ran three experiments testing emotional versus rational ad copy against two kinds of services: ones you can judge by trying them, and ones you can't. A restaurant meal or a plane flight is a service you can judge the moment you've had it, what marketing research calls an experience service. A root canal or a hospital stay requires trusting a professional's judgment, since you may never fully know if the work was right, what's called a credence service.

The authors report that "an emotional advertising appeal led to a higher purchase intention in the experience service condition, while a rational message generated higher purchase intention in the credence service condition." In plain terms: people choose restaurants on feeling and dentists on credentials. Tested across a restaurant-versus-dentist pair and an airline-versus-hospital pair, the pattern held both times. The dentist and the hospital needed credentials, specifics, and reasons to trust the work. The restaurant and the airline needed to make someone feel something before they'd booked anything.

That's a clean rule, but it's not the only variable at work, and treating it as the whole answer is where owners get into trouble. What actually moves people depends on the specific business and the specific goal behind the ad, which is why Knowing learns your business first and judges the ad second.

Involvement matters as much as category.

A separate study by Mahsa Akbari compared rational and emotional appeals across a low-involvement product, sunscreen, and a high-involvement one, a laptop. The common assumption is that cheap, low-stakes purchases are won on feeling and big, complicated ones are won on logic. Akbari's results actually line up with a well-established idea in persuasion research: when people aren't thinking hard about a decision, they lean on feeling, and when they're thinking hard, they lean on logic. Her data confirmed it: "for low involvement products emotional appeals have a more significant effect on advertising attitude, for high involvement products rational appeals are more influential."

That matters for a service business because involvement and service type aren't the same axis. A $20 haircut is low involvement and high experience: emotion probably wins on both counts. But a $20 one-time home inspection might be low-cost and still feel like a serious decision to the customer, because getting it wrong is expensive later. The owner has to ask how much thought the customer is actually putting into the decision, not just what the service costs.

The question isn't whether people buy on emotion or on logic. It's which one feels like the safer bet to the specific person deciding.

Combining both doesn't just split the difference.

It's tempting to hedge: put a warm photo and a bullet list of credentials in the same ad, and cover both bases. A study by Seunghwan Lee and Bob Heere, run on sports fans rather than a general consumer pool, tested purely emotional ads against purely rational ads against combined ads. The emotional-only ads won outright: higher attitude toward the ad, higher brand attitude, higher purchase intent, and more actual merchandise bought, compared to both the rational and the combined versions. Folding in rational content didn't add persuasion. It diluted the emotional pull without buying any credibility in return.

That's a specific, sports-fan context, and it shouldn't be read as a universal law against ever using facts. It doesn't mean skip facts entirely; it means lead with the appeal your customer already expects, rather than splitting the ad evenly between both. An emotional ad and a rational ad are doing different jobs, and running both halfheartedly in the same thirty seconds can leave you with neither.

The audience isn't one person anyway.

Even within a single service category, people don't respond the same way. A 2020 study by researchers writing in Sustainability using smartphone ad copy sorted consumers into hidden groups based on how they actually responded, not how they described themselves: a rational-leaning group of 68 people, an emotional-leaning group of 74, and a third group driven mainly by plain usefulness. Nobody told the researchers which group they belonged to. The groups showed up in the data.

A separate experiment on travel advertising, published in the Annals of Tourism Research in 2022, adds another layer: the right appeal depends partly on what people already believe about the thing being advertised. The researchers found that emotional appeals worked better for destinations with a reputation for warmth, while rational appeals worked better for destinations with a reputation for competence, a pattern they tie to cognitive ease, meaning the message feels easier to take in when it matches what the audience already expects. A dentist's office already carries a competence reputation walking in the door. Fighting that with a warm, feelings-first ad may be working against the grain instead of with it.

What this means for the ad you're about to run.

None of this says emotional ads are soft or rational ads are boring. It says the fit between the appeal and the service is the thing to get right, and that fit depends on two questions an owner can actually answer: can the customer judge this service for themselves once they've experienced it, or are they trusting your expertise on faith? And how much thought is the customer realistically putting into this purchase, regardless of the price tag?

A salon owner selling a $40 haircut probably wants the photo that makes someone feel something. A plumber pitching a $4,000 repipe job, where the customer can't verify the work until it's behind a wall, probably wants the licensed-and-insured line, the before-and-after, the warranty. Both are legitimate advertising strategies. Neither is the default, and running the wrong one isn't a matter of taste, it's a mismatch the research keeps finding.