Latest / The Copywriting Podcast with Fexingo: Sales Letters, Headlines, and Persuasive Writing / How One Underlined Word Lifted Response by 87 Percent
Transcript
- Lucas: Let me tell you about a single underlined word that lifted response by 87 percent. Luna: Eighty-seven percent from one word? That's the kind of number that makes you question everything you think you know about copy. Lucas: Exactly. The test was run by the American Cancer Society back in the 1970s. They were sending out a fundraising letter, pretty standard for the time. But they decided to split-test one variable: they underlined a single word in the body copy. Luna: Which word? Lucas: The word was 'you'. They underlined 'you' in a sentence that said something like, 'This is important for you.' The control version had no underlining. The variant had that one word underlined. And the variant outperformed the control by 87 percent in donations. Luna: So it wasn't a different headline or a stronger call to action. It was just a typographic choice — a simple line under a pronoun. Lucas: Right. And that's what makes it so fascinating. It suggests that the brain processes emphasis cues unconsciously, and that underlining, specifically, taps into a kind of pre-digital reading habit. It signals, 'Pay attention, this word matters.' Luna: I wonder if the same test would work today. We're so used to bold, italics, colour, animation. Underlining feels almost old-fashioned — especially because on the web, underlined text usually means a link. Lucas: Great point. In fact, many web designers strip underlining from all non-link text precisely to avoid confusion. So the same technique might backfire online. But that doesn't mean the principle is dead. It means we have to find the modern equivalent. Luna: What would that be? A different colour? A highlight? A bolded word? Lucas: I've seen tests where a single bolded word in an email subject line lifts open rates by 10 to 20 percent. But the key is restraint. If you emphasise everything, you emphasise nothing. The power comes from isolating one element and making it visually distinct. Luna: The American Cancer Society test is a classic example of that. I've also read about a test where underlining the word 'now' in a call to action button lifted click-throughs significantly. But again, that was in print. Lucas: Let's talk about the psychology for a second. Underlining works because it mimics the way we physically mark up text when we're studying — it's an act of emphasis that feels handcrafted. It breaks the monotony of uniform type. And because it's rare, it stands out. Luna: So it's scarcity in visual form. If every other word had a line under it, the reader would tune out. But one single underlined word? That's an invitation to pause. Lucas: Exactly. And in the American Cancer Society case, that pause likely led the reader to personalise the message. The word 'you' is already powerful — it directly addresses the reader. Underlining it reinforces the idea that this letter is about them, not a generic audience. Luna: It's almost like a whisper in a loud room. Everyone else is shouting, and you lean in to hear the one quiet voice. The underlining creates that quiet emphasis. Lucas: That's a great metaphor. And it speaks to a broader principle in copywriting: the most powerful techniques are often the simplest. You don't need a flashy design or a complicated offer. Sometimes a tiny tweak — a single underlined word — can double your response. Luna: Let's talk about where this technique is still applicable today. Obviously, in direct mail it still works. But what about email? Or landing pages? Lucas: For email, I'd experiment with underlining a key word in the preheader text or in a short paragraph. But you have to be careful that the underline doesn't look like a link. Some email clients still render underlined text as clickable. So maybe use bold instead. But the principle holds. Luna: Yeah, the goal is the same: draw the eye to the most important word. In a landing page, you might underline a single word in the headline or in the call to action button. I've seen tests where underlining the word 'free' in a button text increased clicks by 15 percent. Lucas: And there's a psychological reason for that, too. Underlining a word like 'free' or 'now' or 'you' gives it weight. It signals that this is the core of the offer. The reader doesn't have to guess what matters — you're telling them. Luna: But I've also seen tests where overusing underlining actually hurt response. One marketer underlined three words in a single paragraph, and the control beat it by 12 percent. So restraint is key. Lucas: Absolutely. The rule of thumb is: one underline per piece of copy. Maybe two if the piece is very long. But never more. And always underline the word that carries the emotional or action-oriented weight. Luna: So if I'm writing a donation letter today, I'd underline 'you' or 'now'. If I'm selling a product, I might underline 'guaranteed' or 'risk-free'. What about you, Lucas? Lucas: I'd underline the word that encapsulates the benefit. For example, in a headline like 'Double your sales in 30 days,' I'd underline 'double'. That's the promise. That's what the reader wants. By underlining it, you're saying, 'Yes, that's the point.' Luna: And I think that's the key takeaway: underlining is a form of vocal emphasis on the page. It's like saying the word a little louder. But if you shout every word, you're just yelling. Lucas: Exactly. And speaking of emphasis, there's a related technique that often gets overlooked: using a different colour for a single word. In print, that might be red ink. Online, it's a hex code. I've seen tests where a single red word in a black and white letter lifted response by 40 percent. Luna: So the principle is broader than just underlining. It's about isolating one element and making it visually different. The brain can't help but notice the outlier. Lucas: Right. And that's why these old tests are still valuable. They teach us about human psychology, not just about specific tactics. The tactic might change, but the psychology remains. Luna: Honestly, if today's episode sparked something you've actually used — maybe you're going to test underlining in your next email or landing page — then it might be worth a coffee to you. If so, there's a link at buy me a coffee dot com slash fexingo. Just a small way to keep the show ad-free and running. Lucas: Yeah, we appreciate that. And now back to the psychology. There's another fascinating angle: underlining works because it creates a moment of intimacy. It's like the writer is reaching out and tapping the reader on the shoulder. Luna: I love that. It's a physical gesture translated into typography. And in a world of sterile digital text, that human touch can be powerful. Lucas: So if you're writing copy today — whether it's a sales letter, an email, or a social media post — ask yourself: what is the one word that, if the reader remembers nothing else, they must remember? That's your candidate for emphasis. Luna: And then test it. Because the 87 percent lift in the American Cancer Society test might not replicate in every situation. But the odds are good that some version of that technique will work for you. Lucas: I'd love to hear from listeners who test this. Drop us a note — we're on social media as Fexingo. And if you want to dig deeper into the archives, we have over a hundred episodes on these micro-tactics. Luna: Next time, we'll look at the opposite: what happens when you remove all emphasis? Spoiler: sometimes it works better. See you then. Lucas: See you then.