Emerging word segmentation abilities in European Portuguese-learning infants: new evidence for the rhythmic unit and the edge factor.

Word segmentation plays a crucial role in language acquisition, particularly for word learning and syntax development, and possibly predicts later language abilities. Previous studies have suggested that this ability develops differently across languages, possibly affected by the languages' rhythmic properties (Rhythmic Segmentation Hypothesis) and target word location in the prosodic structure (Edge Hypothesis). The present study investigates early word segmentation in a language, European Portuguese, that exhibits both stress- and syllable-timed properties, as well as strong cues to both higher-level prosodic boundaries and the word level. Infants aged 4-10 months old were tested with target words located in utterance-medial and utterance-final positions. Evidence for word segmentation was found early in development but only for utterance-edge located target words, suggesting the more salient prosodic cues play a crucial role. There was some evidence for segmentation in utterance-medial position by 10 months, demonstrating that this ability is not yet fully developed, possibly due to mixed rhythmic properties.