During the first two years of life, infants concurrently refine native-language speech categories and word learning skills. However, in the Switch Task, 14-month-olds do not detect minimal contrasts in a novel object--word pairing (Stager & Werker, 1997). We investigate whether presenting infants with acoustically salient contrasts (liquids) facilitates success in the Switch Task. The first two experiments demonstrate that acoustic differences boost infants' detection of contrasts. However, infants cannot detect the contrast when the segments are digitally shortened. Thus, not all minimal contrasts are equally difficult, and the acoustic properties of a contrast matter in word learning.