While minstrel-styled wordplay humor was common in the formative years of the program, it was used less often as the series developed, giving way to a more sophisticated approach to characterization. Correll and Gosden were fascinated by human nature, and their approach to both comedy and drama was drawn from their observations of the traits and motivations that drive the actions of all people. While their characters often overlapped popular African-American stereotypes, there was also a universality to their characters which transcended race; beneath the dialect and racial imagery, the series celebrated the virtues of friendship, persistence, hard work, and common sense, and as the years passed and the characterizations were refined, "Amos 'n' Andy" achieved an emotional depth rivaled by few other radio programs of the 1930s.