ManyBabies 3: 30 labs, 839 infants fail to replicate landmark infant rule-learning finding

AndrewLampinen · x · 2026-09-29

ManyBabies 3, an open-access registered report in Developmental Science, brought together 30 labs across 33 languages testing 839 infants to replicate the textbook 1999 finding from Gary Marcus et al. that 7-month-olds learn abstract rules from speech.

The result: they did not find it. The massive replication effort challenges a foundational claim in infant cognition and weakens a key line of evidence often cited in debates over language acquisition and learning theory.

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