Latest / The Copywriting Podcast with Fexingo: Sales Letters, Headlines, and Persuasive Writing / How One Underlined Word Lifted Response by 42 Percent
Transcript
- Lucas: If you've been listening to this show for a while, you know I'm a sucker for tiny changes that produce outsized results. Today's example might be the smallest yet: one underlined word. Luna: One word? Underlined? That's it? Lucas: That's it. And it lifted response by 42 percent. This comes from a direct mail test done in the 1970s for a veterans' charity. The control package was already performing well — it had a strong letter, a compelling story, a clear ask. The only difference in the test was that the copywriter underlined a single word in the body copy. Luna: Which word? Lucas: The word 'you.' Specifically, the sentence read: 'This is your chance to make a difference.' In the control, it was just a normal sentence. In the test, 'your' was underlined. That's all they changed. Luna: And that lifted response by 42 percent? I mean, I get that 'you' is a powerful word in copywriting, but an underline? Lucas: I know. It sounds almost too simple. But the data held up over multiple mailings. The underline acted as what you might call a 'cognitive highlighter.' It told the reader's brain: pay extra attention here. And because the word was 'your,' it also reinforced the personal relevance. Luna: So it's a double whammy — the personal pronoun plus the visual emphasis. Lucas: Exactly. And this is where the psychology gets interesting. When you underline a word, you're essentially adding a nonverbal cue that says 'this matters.' In a medium like direct mail, where the reader is scanning quickly, that cue can be the difference between a glance and a read. Luna: But could it also backfire? Like, if you overuse underlines, don't they lose their power? Lucas: Absolutely. And I think that's the key lesson here — it's not that underlines always work. It's that strategic underlines, used sparingly, can direct attention effectively. In the veterans' letter, there was only one underline in the entire piece. That's what made it stand out. Luna: So the principle is: one emphasis per piece. Not five, not ten. One. Lucas: Right. Think of it like a single exclamation mark in a 500-word email. One feels intentional. Two feels desperate. Three feels like spam. Luna: That's a good rule of thumb. I'm thinking about how this translates to digital copy. We don't underline much anymore on the web because it looks like a link. Lucas: That's a great point. Underlining in digital is almost always associated with hyperlinks now. So the same technique won't work in an email or on a landing page — it'll just confuse the reader. But the principle behind it — visual emphasis — is still valid. You just need to use the right tool for the medium. Luna: Like bolding a key word. Or using a different color. Or even adding a subtle icon. Lucas: Exactly. I've seen tests where bolding a single word in an email subject line lifted open rates by 15 to 20 percent. Same mechanism: you're telling the reader's brain to stop and process. Luna: Before we dig deeper into that, I want to mention something. We get a lot of questions about how we keep this podcast ad-free. The answer is simple: listeners like you who choose to support it. If these copywriting examples have ever sparked a test you ran, or a headline you wrote that worked, and you want to help keep the show free of sponsors, the link is buy me a coffee dot com slash fexingo. No pressure, just an option. Lucas: Yeah, it's a small way to keep the conversation going without having to sell you something in the middle of it. Appreciate anyone who's ever chipped in. Luna: Alright, back to the underline. Lucas, you mentioned the test was from the 1970s. Are there more recent examples of this principle in action? Lucas: There are. One that comes to mind is from a 2019 A/B test run by a nonprofit that sends monthly appeal letters. They tested underlining the word 'now' in the call to action: 'Donate now.' The underlined version outperformed the control by 18 percent. Luna: So the underline works on urgency words too. Lucas: Yes. But again, only if it's the only emphasis in the piece. In that same test, they tried underlining both 'Donate' and 'now' — and response dropped back to the control level. Luna: That's fascinating. So the brain interprets multiple underlines as noise, not signal. Lucas: Exactly. And this connects to a broader principle in persuasion: scarcity of attention. If you try to emphasize everything, you emphasize nothing. Luna: So the practical takeaway for a copywriter today: pick one word — ideally a personal pronoun or an urgency word — and emphasize it. Just once. And test it. Lucas: And test it. That's the most important part. What worked for a veterans' charity in the 1970s might not work for your SaaS product in 2026. But the underlying behavior — that a single, strategic visual cue can increase response — is almost certainly still true. Luna: I want to try this in an email I'm writing later this week. I'll underline 'you' in the opening line — but I'll do it in bold, not underline, so it doesn't look like a link. Lucas: Good call. And if you do, let me know how it performs. We can share the results on a future episode. Luna: I will. So, final thought: the underline isn't a magic bullet. It's a reminder that small, intentional details can have big effects. And that sometimes the simplest change is the one that works best. Lucas: Well said. That's our show for today. Thanks for listening — we'll be back on Monday with another copywriting story.