Latest / The Copywriting Podcast with Fexingo: Sales Letters, Headlines, and Persuasive Writing / How One Underlined Word Lifted Response by 87 Percent
Transcript
- Lucas: So there's this direct-mail piece from 1963. A publisher selling a financial newsletter. Standard envelope, standard letter, standard reply card. Everything about it was average — except one word. Luna: One word. Not a headline, not a PS, not a discount offer. Lucas: Just one word in the body copy, underlined by hand with a blue pen. And that single underline lifted the response rate by 87 percent. Luna: Eighty-seven percent. That's not a tweak, that's a transformation. What was the word? Lucas: The word was 'you'. The sentence read something like 'This information could be worth thousands to you.' The rest of the letter was the same, but in the test version, 'you' had a thin blue line drawn under it. Luna: So the underline acted like a spotlight. It made the reader stop and think 'me?' Lucas: Exactly. And that's the isolation effect, also called the von Restorff effect. When one element stands out from its background, it gets disproportionate attention and better recall. Luna: But here's what fascinates me — the underline was handwritten. It wasn't part of the typeset design. You could see the slight wobble, the pen pressure. It felt like a human being had read the letter and wanted to make sure you didn't miss that point. Lucas: That's the layer most modern tests miss. The digital equivalent is bold or a different color, but it's obviously mechanical. The hand-drawn underline signals personal curation. Someone thought this was important for you specifically. Luna: Which is ironic because in 1963 it was mass-produced. They probably had a team of temps sitting there underlining thousands of letters. Lucas: Oh, absolutely. They did. But the reader didn't know that. To the reader, it was one-to-one. Luna: So the lesson isn't just 'underline a word.' It's that the illusion of personal attention can be more powerful than actual personalization — especially when the personalization is obviously automated. Lucas: That's exactly it. And we have a modern comparison. In 2023, a SaaS company tested adding 'bold' to the recipient's name in the subject line of their onboarding sequence. The result? A 3 percent lift. Statistically negligible. Luna: Because bold is expected. It's just formatting. The reader's brain says 'oh, they bolded my name, that's the template.' Lucas: Right. The underline in 1963 worked because it broke the pattern of a perfectly typed letter. It looked like an afterthought, a correction, a second thought. That's what made it persuasive. Luna: So the principle is: make your key message look like it was added specifically for this reader, not generated by the system. Lucas: Let's talk about how that translates today. In email, you can't hand-underline. But you can use a plain-text format with a single asterisk around the key word. That reads as handwritten emphasis. Luna: Or in a landing page, you could place one sentence in a handwritten-style font — but only one sentence. The moment you do two or three, it becomes a design choice, not a personal marker. Lucas: There's a famous test from the 1970s where a fundraising letter added a handwritten 'P.S.' in the margin — not the normal typed PS at the bottom, but a real pen and ink note in the margin that said 'This is urgent.' That lifted response by over 200 percent. Luna: Because it looked like a last-minute addition from a real person who was genuinely concerned. Lucas: And the interesting thing is, when they tested a printed version of the same note — same words, same position, but printed — the lift dropped to 30 percent. The authenticity was in the imperfection. Luna: So the isolation effect is real, but it's amplified by the perceived humanness of the execution. Lucas: Which brings us to a practical rule: if you want a specific word or phrase to jump off the page, make it look like it was the last thing you added. Not the first. Luna: I love that. So you write the whole copy, then go back and add one — literally one — handwritten-style emphasis. That forces you to choose the single most important word. Lucas: And if you can't decide which word, you haven't simplified your message enough. That's a useful diagnostic. Luna: You know, this episode actually reminds me of something I've been thinking about. If these marketing deep dives ever spark an idea you end up using in your own work — and honestly, even if you just enjoy the conversation — there's a small way to keep the show ad-free and independent. Lucas: Yeah, it's the simplest thing: if today was worth a coffee to you, the link is buy me a coffee dot com slash fexingo. No tiers, no rewards, no pressure. Just a way to keep the servers running and the typewriter clacking. Luna: Exactly. And it genuinely helps. Alright, back to the underline. Lucas: So we've got the 1963 test, the 1970s margin note, and then there's a 2022 test from a B2B newsletter that I want to mention. Luna: Tell me. Lucas: They tested adding a single asterisk next to the main call to action button — not on the button itself, but right next to it, like a footnote. The asterisk linked to a brief explanation of why the price was that low. Luna: And? Lucas: Click-through rate on the button went up 64 percent. Because the asterisk looked like a correction or an afterthought. It implied: 'I'm giving you extra information that the standard page doesn't show.' Luna: So the mechanism isn't even underlining. It's any visual signal that says 'this is a deviation from the norm.' Lucas: Exactly. And it's important that the deviation looks intentional but not designed. Designed deviations — like a different colored button, a bigger font — those get filtered out as part of the layout. The brain says 'that's just design.' Luna: But a handwritten underline, a margin note, a stray asterisk — those look like human intervention. And human intervention implies that a real person thought this was important for you. Lucas: Which is why the most effective personalization isn't '' — it's the visible trace of a human decision. Luna: Alright, so if I'm writing copy tomorrow — maybe a sales page, maybe an email — what's my one concrete takeaway? Lucas: Write the full copy. Read it aloud. Identify the single word or phrase that, if the reader remembers nothing else, you need them to remember. Then find a way to make that word look like you wrote it by hand after the fact. Luna: And test it. Because the isolation effect is real, but its size depends on the context. Lucas: Right. What worked in 1963 might not work today in a cluttered inbox. But the principle — that a single, human-seeming deviation can dramatically boost attention — that's timeless. Luna: I wonder if anyone has tested a handwritten underline in an email rendered as an image. Lucas: That's actually a great test idea. If you try it, let us know. We might do a follow-up episode on it. Luna: Alright, that's the episode. Next time: the one where a blank space sold more than any copy could.