How a Single Underline Boosted Response by 47 Percent

In this episode of The Copywriting Podcast with Fexingo, Lucas and Luna examine a direct mail test from the 1970s where a single typographical change — underlining a key phrase in a sales letter — lifted response rates by 47 percent. They trace the discovery back to copywriter Herschell Gordon Lewis, who documented the test in his book 'The Direct Mail Copy That Sells.' The hosts discuss why underlining worked psychologically: it signaled emphasis without shouting, it mimicked the natural human gesture of pointing, and it gave the reader's eye a visual anchor in a block of text. They also explore modern equivalents: bold text, italics, bullet lists, and the dangers of over-formatting. Luna pushes back with a counter-case from a 2019 email split test where underlining actually dropped click-through rates; Lucas explains context matters — the medium, the audience, and the degree of emphasis all play a role. The episode ends with a practical takeaway: test one emphasis technique per campaign, measure the shift, and let data override instinct. #Copywriting #DirectMail #HerschellGordonLewis #SalesLetters #Typography #A_BTesting #ResponseRate #Persuasion #MarketingPsychology #EmphasisInCopy #UnderlineTest #DirectResponse #Marketing #Business #FexingoBusiness #BusinessPodcast #TheCopywritingPodcast #WritingTips Keep every episode free: buymeacoffee.com/fexingo