Digging up the building blocks of language: Age-of-acquisition effects for multiword phrases

• Early acquired words show processing advantages in adult language.
• We show that like words, multiword phrases also show Age-of-Acquisition effects.
• Early-acquired phrases are processed faster in adulthood.
• After controlling for adult frequency, plausibility and lexical AoA.

Words are often seen as the core representational units of language use, and the basic building blocks of language learning. Here, we provide novel empirical evidence for the role of multiword sequences in language learning by showing that, like words, multiword phrases show age-of-acquisition (AoA) effects. Words that are acquired earlier in childhood show processing advantages in adults on a variety of tasks. AoA effects highlight the role of words in the developing language system and illustrate the lasting impact of early-learned material on adult processing. Here, we show that such effects are not limited to single words: multiword phrases that are learned earlier in childhood are also easier to process in adulthood. In two reaction time studies, we show that adults respond faster to early-acquired phrases (categorized using corpus measures and subjective ratings) compared to later-acquired ones. The effect is not reducible to adult frequencies, plausibility, or lexical AoA. Like words, early-acquired phrases enjoy a privileged status in the adult language system. These findings further highlight the parallels between words and larger patterns, demonstrate the role of multiword units in learning, and provide novel support for models of language where units of varying sizes serve as building blocks for language.