Procedural learning across the lifespan: A systematic review with implications for atypical development.

This systematic review aimed to investigate procedural learning across the lifespan in typical and atypical development. Procedural learning is essential for the development of everyday skills, including language and communication skills. Although procedural learning efficiency has been extensively studied, there is no consensus yet on potential procedural learning changes during development and ageing. Currently, three conflicting models regarding this trajectory exist: (1) a model of age invariance; (2a) a model with a peak in young adulthood; and (2b) a model with a plateau in childhood followed by a decline. The aims of this study were (1) to investigate this debate on procedural learning across the lifespan by systematically reviewing evidence for each model from studies using the serial reaction time task; and (2) to review procedural learning in autism spectrum disorder (ASD) and specific language impairment (SLI), two developmental disorders characterized by deficits in communication skills, in the light of these models. Our findings on typical development strongly support a model of age-related changes (Model 2a or 2b) and show that mixed findings regarding the developmental trajectory during childhood can be explained by methodological differences across studies. Applying these conclusions to systematic reviews of studies of ASD and SLI makes it clear that there is a strong need for the inclusion of multiple age groups in these clinical studies to model procedural learning in atypical development. Clinical implications of the findings are discussed. Future research should focus on the role of declarative learning in both typical and atypical development.