Doubly blessed: older adults know more vocabulary and know better what they know.

This study examined age-related differences in the ability to judge one's vocabulary. Young, middle-age, and older adults completed a multiple-choice test of vocabulary, judged their confidence in each answer, and estimated their overall performance. Older adults performed better and were more confident in their knowledge than were the other 2 groups. Importantly, relative to young adults, older adults demonstrated better calibration both on item-by-item confidence judgments and on global estimates. Resolution, as defined by correlations between item-by-item performance and confidence judgments, was age-invariant. We suggest that age-related accumulation of vocabulary is accompanied by enhanced perception of mastery in one's knowledge.