Why Do Children Think Words Are Mutually Exclusive?

idea is that children rely on an inductive bias that ensures that novel words get assigned distinct meanings from known
words—mutual exclusivity. Here, we explore the possibility that mutual-exclusivity phenomena do not reflect a bias
but rather information encoded in the message. Learners might effectively be told when (and when not) to assume
that word meanings are mutually exclusive. In three experiments (N = 106 from across the United States; ages 2 years,
0 months−2 years, 11 months), we show that 2-year-olds only assumed that novel words have distinct meanings if
the words were spoken with focus, an information-structural marker of contrast. Without focus, we found no mutual
exclusivity; novel words were understood to label familiar objects. These results provide a novel account of mutual
exclusivity and demonstrate an early emerging understanding of focus and information structure.