How a Single Underline Boosted Response by 47 Percent

The Copywriting Podcast with Fexingo: Sales Letters, Headlines, and Persuasive Writing · Jun 2, 2026 · 8m · transcript

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…