Mothers modify their actions when demonstrating objects to infants versus adults.Such modifications have been called infant-directed action (IDA) or mofionese (Brand, Baldwin, & Ashburn, 2002). We investigated the IDA features of interactiveness and simplification by quantifying eye gaze, object exchanges, and action units enacted between exchanges in 42 mothers' demonstrations of novel objects to infants (6-8 months or 11-13 months) or adults. We found more eye gaze, more object exchanges, and fewer action types per turn in demonstrations to infants relative to adults. Unlike prior research using global measurements, we detected differences in behavior directed at infants of different ages: Shorter, more frequent gazes and more exchanges characterized demonstrations to older versus younger infants. These findings indicate the fruitfulness of fine-grained analysis of IDA, and further clarify how adults may support infants' processing of human motion.Despite the complexities in their everyday social environment, infants make rapid progress in analyzing incoming streams of information. In the action domain, for instance, infants can parse dynamic behavior streams into intention-relevant units by 9 months of age (