both the target article and the precommentary demonstrate that relatively simple biobehavioral processes have the cumulative effect of fostering behavioral outcomes characteristic of attention-deficit/hyperactivity disorder (adhd). as such, the articles illustrate a central theme of darwinian thinking – basic processes acting over time can produce complex and diverse outcomes. in this commentary, we indicate that tracing the action of processes over time can be facilitated by quantitative methods such as artificial neural networks.