ABSTRACTPrevious research shows that English-learning 7.5-month-olds are biased to segment speech at strong syllables consistent with the predominant trochaic (strong-weak) pattern of words in their language (Jusczyk, Houston, & Newsome, 1999). The present study asked whether 7.5-month-olds can use a familiar name to override their metrical bias and segment iambic (weak-strong) words from natural speech. Infants were familiarized to passages containing weak-strong-weak sequences (guiTAR is) preceded by Mama/Mommy or an unfamiliar name. Infants were tested on iambic words (guiTAR in Experiments 1–2) or trochaic nonwords (TARis in Experiment 3). Segmentation occurred only for iambic words that were preceded by Mama/Mommy during familiarization. The presence of Mama/Mommy attenuated infants’ bias to treat strong-syllables as word onsets. We suggest that young infants weight highly familiar words more strongly than metrical information and discuss the implications of this finding for a hierarchical model of s...