Characterising developmental disorders: Towards better group comparisons in developmental research

Investigating a developmental disorder (DD) must consider three questions: 1) Who are you measuring? 2) How are you measuring? and 3) What are you measuring? The decisions made – from selecting an appropriate comparison group and deciding what to match on, to the very measurements and statistics we use – directly inform the characterisations of a DD. We discuss the implications of these decisions through a critique of approaches: Including coping with heterogeneity, group matching and the importance of studying processes as well as outcomes. Our aim is to help researchers navigate this field of research and make informed decisions.