Action initiation and punishment learning differ from childhood to adolescence while reward learning remains stable

Theoretical and empirical accounts suggest that adolescence is associated with heightened reward learning and impulsivity. Experimental tasks and computational models that can dissociate reward learning from the tendency to initiate actions impulsively (action initiation bias) are thus critical to characterise the mechanisms that drive developmental differences. However, existing work has rarely quantified both learning ability and action initiation, or it has tested small samples. Here, using computational modelling of a learning task collected from a large sample (N=742, 9-18 years, 11 countries), we tested differences in reward and punishment learning and action initiation from childhood to adolescence. Computational modelling revealed that whilst punishment learning rates increased with age, reward learning remained stable. In parallel, action initiation biases decreased with age. Results were similar when considering pubertal stage instead of chronological age. We conclude that heightened reward responsivity in adolescence can reflect differences in action initiation rather than enhanced reward learning.