CUE: the continuous unified electronic diary method.

In the present article, we introduce the continuous unified electronic (CUE) diary method, a longitudinal, event-based, electronic parent report method that allows real-time recording of infant and child behavior in natural contexts. Thirty-nine expectant mothers were trained to identify and record target behaviors into programmed handheld computers. From birth to 18 months, maternal reporters recorded the initial, second, and third occurrences of seven target motor behaviors: palmar grasp, rolls from side to back, reaching when sitting, pincer grip, crawling, walking, and climbing stairs. Compliance was assessed as two valid entries per behavior: 97 % of maternal reporters met compliance criteria. Reliability was assessed by comparing diary entries with researcher assessments for three of the motor behaviors: palmar grasp, pincer grip and walking. A total of 81 % of maternal reporters met reliability criteria. For those three target behaviors, age of emergence was compared across data from the CUE diary method and researcher assessments. The CUE diary method was found to detect behaviors earlier and with greater sensitivity to individual differences. The CUE diary method is shown to be a reliable methodological tool for studying processes of change in human development.