This project site contains the methods, data, analysis scripts, and pre-registration for a project on trajectories of attachment styles from childhood through adolescence. The questionnaire items are contained in the folder called *Methods*. The data are contained in the folder named *Data*. The data file is a raw comma-delimited text file with variable names in the headers. The variable names are explained in the analysis script for R. The R workspace (containing the data) has also been uploaded as a work-around for users who encounter trouble in downloading or using the raw data. The analysis script for R is designed to automate the downloading and processing of the data. It produces automatically all analyses and graphs reported in the manuscript. Although it is an R script, it can be viewed and edited as a raw text file. The pre-registration for the analysis plan is listed in the pre-registration document. The plan was drafted before the data were received and analyzed.