Learning Words Over Time: The Role of Stimulus Repetition in Mutual Exclusivity

During the second year of life, infants develop a preference to attach novel labels to novel objects. This behavior is commonly known as “mutual exclusivity” (Markman, 1989). In an intermodal preferential looking experiment with 19.5‐ and 22.5‐month‐olds, stimulus repetition was critical for observing mutual exclusivity. On the first occasion that a novel label was presented with 1 familiar object and 1 novel object, looking behavior was unsystematic. However, on reexposure to the same stimuli, 22.5‐month‐olds looked preferentially at the novel object prior to the re‐presentation of the novel label. These findings suggest a powerful memory mechanism for novel labels and objects, enabling mutual exclusivity to emerge across repeated exposures to potential referents.