Baldwin, DareKosie, Jessica2020-02-272020-02-272020-02-27https://hdl.handle.net/1794/25250Over the first few years of life, infants acquire the ability to make sense of, predict, respond to, remember, and learn from a variety of everyday human actions. Finding segmental structure within unfolding activity – in particular, boundaries at which units of action begin and end – seems key to the acquisition of such action-processing fluency, and has important downstream implications for cognitive and linguistic development (e.g., Levine et al., 2018). However, action unfolds rapidly and is just as quickly gone. How do infants find structure in the complex, dynamic, fleeting action that they observe? Caregivers’ infant-directed action demonstrations might serve to help with this challenging task. In interactions with infants, caregivers modify their motion in a variety of ways that engage infants’ overall attention (i.e., “motionese;” Brand, Baldwin, & Ashburn, 2002). It seems likely that these modifications additionally highlight and promote infants’ processing of the internal structure of action. This dissertation explores the influence of motionese on infants’ online processing of action. We first created a corpus of infant- and adult-directed activity sequences. Next, we use a recently-developed, open source, inexpensive, infant-friendly methodology to measure infants’ pupil dilation as they viewed a select subset of these videos. We found that infants’ pupil size (an indication of attention or cognitive engagement) increased in response to action boundaries, but only for motionese demonstrations. Thus, in addition to engaging overall attention, motionese likely serves to promote infants’ processing of action’s internal structure. These findings set the stage for future work targeting the source of this increased pupil dilation at boundary regions. In sum, this work makes several important contributions to developmental science. First, we have created a large, open video corpus of caregiver-infant interactions. We have also validated a new methodology for addressing any number of novel questions about infants’ processing of visual information as it unfolds over time. Finally, this work provides the first demonstration to date that motionese influences infants’ on-line action processing, and in this way scaffolds their understanding of, and ability to learn from, dynamic, novel activity.en-USAll Rights Reserved.action processingaction segmentationmotionesenatural pedagogypupillometryElectronic Thesis or Dissertation