Précis of The Birth of a Word

Sometime around their first birthday, children typically produce their first word, adding hundreds more to their vocabulary during their second year (Fenson et al., 1994). Learning words is a core task in the larger enterprise of acquiring one’s native language. Researchers often refer to this overall enterprise by the theoretically neutral term “language acquisition”, since there is much debate about where maturational processes end and learning begins. But there is little debate that words themselves are learned through experience. How is this accomplished? What is the trajectory of vocabulary development, and how do different environmental factors contribute to word learning? We approach these questions with a particular theoretical interest in how the structure of a child’s everyday experience contributes to word learning. The primary scientific goal of this work is to study how the rich social interaction and activity structures of daily life ground everyday linguistic experience and support learning. We hypothesize that these structures provide useful learning constraints, and that more contextually constrained words will be more readily learned. More broadly, we aim to characterize the environmental contributions to the learning process, since learning requires not only a learner but also learnable structure. We seek to characterize this learnable structure both in the speech a child hears as well as the broader context in which that speech occurs, and to examine the relationships to word learning. To pursue this scientific goal, we embarked on a naturalistic, observational study of one child’s early word learning, collecting and analyzing data about both the learning environment and what was learned. Our data consist of dense audio and video recordings of the home of a family with a young child, which we collected through the Human Speechome Project (Roy et al., 2006). Using a custom audio-video recording system embedded in the ceilings of every room in the family’s home, we initiated recording at the birth of the child and recorded roughly 10 hours per day until the child’s third birthday, collecting an unprecedented amount of data of one child’s experience and development. As with all observational case studies, there are numerous challenges in working with data collected “in the wild”, but to effectively leverage data at this scale required new methodological solutions. Therefore, in addition to our scientific goal of studying the environmental contributions to word learning, our second goal is to develop methods for annotation and analysis of large-scale observational records. The challenges in working with this data are manifold. Audio and video are not easy to analyze directly but must be annotated, yet fully manual annotation is often exceedingly time consuming and expensive. We develop semiand fully-automatic methods for general tasks such as speech transcription and speaker identification, and explore computational approaches to tasks such as identifying and labeling human activities. With the combination of dense, naturalistic recordings and new methods for large-scale data annotation, we organized our analyses around predicting “word births”, a term we coined to identify