Plain women know more about men than beautiful women do.

The remark contrasts social power based on beauty with knowledge gained through observation and experience. It implies that women who are not treated as “beautiful” may receive fewer flattering projections and fewer social advantages, which can push them to read men’s motives and behavior more carefully. Conversely, “beautiful” women may be insulated by attention and deference, encountering a narrower range of candid male behavior. As a Hepburn-attributed aphorism, it also fits her public persona: skeptical of conventional femininity and alert to the ways gender expectations distort relationships. The line is less a universal claim than a pointed comment on how appearance can shape what one is allowed—or forced—to learn.