BACKGROUND AND OBJECTIVES: Child mobile device use is increasingly prevalent, but research is limited by parent-report survey methods that may not capture the complex ways devices are used. We aimed to implement mobile device sampling, a set of novel methods for objectively measuring child mobile device use. METHODS:We recruited 346 English-speaking parents and guardians of children aged 3 to 5 years to take part in a prospective cohort study of child media use. All interactions with participants were through e-mail, online surveys, and mobile device sampling; we used a passive-sensing application (Chronicle) in Android devices and screenshots of the battery feature in iOS devices. Baseline data were analyzed to describe usage behaviors and compare sampling output with parent-reported duration of use. RESULTS:The sample comprised 126 Android users (35 tablets, 91 smartphones) and 220 iOS users (143 tablets, 77 smartphones); 35.0% of children had their own device. The most commonly used applications were YouTube, YouTube Kids, Internet browser, quick search or Siri, and streaming video services. Average daily usage among the 121 children with their own device was 115.3 minutes/day (SD 115.1; range 0.20-632.5) and was similar between Android and iOS devices. Compared with mobile device sampling output, most parents underestimated (35.7%) or overestimated (34.8%) their child's use. CONCLUSIONS:Mobile device sampling is an unobtrusive and accurate method for assessing mobile device use. Parent-reported duration of mobile device use in young children has low accuracy, and use of objective measures is needed in future research.

Parent smartphone use has been associated with decreased responsiveness to children,(1) fewer verbal and nonverbal interactions,(2) and higher ratings of child externalizing behavior.(3) However, existing studies are limited by use of brief (10-15 minute) observations of parents using smartphones(1, 4) or rely on parent self-report,(3) which may be biased by social desirability. In addition, self-report of smartphone use may be inaccurate due to the brief, intermittent ways users interact with mobile devices,(5) which makes recall difficult.(6) The purpose of this pilot study was to improve upon these measurement limitations by implementing a novel approach-passive mobile sensing-in order to objectively assess parent smartphone use over several days. Passive mobile sensing harnesses data already collected by mobile devices, such as application ("app") or battery usage, and generates usage logs that are transmitted to cloud-based servers or can be emailed to research teams. This Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

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