Figure 1. The sleep habit model to clarifying the daily routine is important for the good sleep habituation in Japanese toddlers.

Squares indicate the “observed variables,” which are the input data, such as the toddler’s wake-up time. Circles with words indicate the “latent variable,” which is the construct that we are unable to directly observe. Circles with “e” and a number are “error variables”—namely, the variables of the other factors of the data that need to be analyzed. Variables that affect “sleep pressure,” “hyperarousal,” “irregularity of schedule,” and “conditioning” and their relationships are shown. All of the standardized estimates show significant differences at **P < 0.001, *P < 0.01.