Recent technological advances and research trends have enabled the collection and analysis of multi-hour or daylong recordings of children’s auditory environment. While this technology has allowed researchers to sample language experience from multiple contexts across the day, challenges remain with respect to how these audio recordings can or should be coded and analyzed. Daylong audio samples have the potential to transform our understanding of the language input that children encounter, but new analysis techniques may be necessary to take advantage of these new opportunities. The present work explores the linguistic content of the transcripts of three daylong recordings with the goal of understanding the content of these recordings in order to develop new ways to analyze and gain insight from these recordings.

Picture book reading is a common activity in the lives of many children. This work describes the frequency andcharacter of picture book reading in American homes. Seventy-seven monolingual English-speaking families with childrenbetween the ages of 18-30 months took part in a 5-day diary study in which caregivers recorded details about picture book read-ing activities. This sample is characteristic of some laboratory samples but less nationally representative; 92.2% of caregiversheld a college degree. Relative to previously reported averages, caregivers reported reading to children more often (6.8x/day),reported beginning reading at a younger age (2.2 months) and reported more books in the home (111.1 books). Caregiversreported both reading the book text and discussing the pictures with their children. These numbers suggest an extremely highupper-limit to the amount of language input some children receive from picture book reading. Consequences for languageenvironments and language development will be discussed.

Shared book reading positively effects language development, yet the causal pathways of this relationship are not un-derstood. Evidence shows that the book complexity modulates caregiver talk, but the link between the book linguisticcomplexity and child syntactic development remains unclear (Noble, et al. 2017). This project describes the speech gen-erated during book reading to see how it differs from typical child-directed speech and whether the picture-book sentencecomplexity is present in the speech that children hear. 10 families with children aged 30-37 months (MBCDI raw vocab-ulary 350-675 out of 680 total) recorded 6-12 picture-book reading sessions in their homes. The books were controlledfor word length (short: 125 words vs long: 1472 words) and syntactic complexity according to the 8 categories analyzedin Montag (2019): complex (17 tokens) vs. simple (0-7 tokens). The caregiver and child speech syntactic complexitymodulation as a function of picture-book syntactic complexity will be discussed.

While naturalistic daylong audio recordings of children’s auditory environments have the potential to reveal key insights about the input children receive and inform our theories of language development, it also presents various methodological hurdles. In the present work, we used three fully transcribed daylong audio recordings to investigate the challenge of manually extrapolating aggregate statistics and quantify the kinds of sampling choices daylong researchers can make. Our findings highlight sampling choices that maximize sampling from the full distribution of the day and potential tradeoffs between human effort and obtaining accuracy.

Why do children learn some words before others? Understanding individual variability across children and also variabilityacross words, may be informative of the learning processes that underlie language learning. We investigated item-basedvariability in vocabulary development using lexical properties of distributional statistics derived from a large corpus ofchild-directed speech. Unlike previous analyses, we predicted word trajectories cross-sectionally, shedding light on trendsin vocabulary development that may not have been evident at a single time point. We also show that whether one looksat a single age group or across ages as a whole, the best distributional predictor is whether a child knows a word is thenumber of other known words with which that that word tends to co-occur.

Reading to young, pre-literate children is associated with better language and reading outcomes, but the underlying mechanisms are poorly understood. The goal of this work is to better understand the potential mechanisms. We hypothesized that vocabulary diversity and sentence complexity might vary between picture books and child-directed speech, and we wanted to quantify those potential differences. We built a corpus consisting of the text of 100 picture books that caregivers might read to pre-literate children. We compared the distributions of vocabulary and certain complex sentences of that corpus to child-directed speech from the CHILDES corpus. We found that picture books contained a higher number of unique word types for a given number of tokens, and contained a higher proportion of complex sentences. The mechanisms by which shared book reading may contribute to improved language outcomes is by exposing children to words and sentence structures that they would not encounter otherwise.