To illuminate individual differences in the development of attention-deficit hyperactivity disorder (ADHD) symptoms in the general population, psychometric measures are needed that can capture general population-level symptom variation reliably, validly, and comparably from childhood through to the transition to adulthood. The ADHD subscale of the…

Recently, there has been an increased interest in the associations between theory of mind (ToM), the ability to infer others' mental states, and academic functioning in middle childhood including scientific reasoning. This study follows this trend and addresses two gaps in the literature. First, it examines whether individual differences in ToM…

Current theories of loneliness posit that biases in social information processing play a key role in the development and maintenance of loneliness. However, this assumption has rarely been tested in longitudinal research in adolescence. The current study concentrated on two constructs associated with such biases, that is, fear of negative…

First-order theory of mind (ToM) development has shown to conform to a Guttman scale, with desire reasoning developing before belief reasoning. There have been attempts to test for internal consistency and scalability in advanced ToM, but not over a broad age range and only with a limited set of tasks. This 2-year longitudinal study (N = 155;…

Prediction from early development to later achievement has the potential to improve clinical and educational service delivery as well as to inform developmental theory. In this longitudinal study, we asked how well can educational achievement measured in the final year (Grade 9, age 15) of compulsory education--both overall and for outcomes in the…