This study explored the impact of infant-directed speech (IDS) versus adult-directed speech (ADS) on neural activity to familiar and unfamiliar words in 6- and 13-month-old infants. Event-related potentials were recorded while infants listened to familiar words in IDS, familiar words in ADS, unfamiliar words in IDS, and unfamiliar words in ADS. The results indicated that IDS elicited increased neural activity compared to ADS for both age groups. Six-month-olds showed a boost in neural activity to IDS for familiar words only. Thirteen-month-olds exhibited increased brain activity to IDS for both familiar and unfamiliar words. The results suggested that IDS changed as a function of development and word familiarity and served as an attentional spotlight to increase brain activity to potentially meaningful words. (Contains 2 tables, 10 figures, and 3 footnotes.)