Finite case series or infinite single-case studies? Comments on "Case series investigations in cognitive neuropsychology" by Schwartz and Dell (2010).

In this commentary, though acknowledging that a case-series approach in neuropsychology is not always possible, we set out a series of considerations that in our view make this approach generally superior to single-case study. We argue that case-series designs are crucial for theory-testing, assessment of computational models, evaluation of inter-patient variation (including selection criteria, patient homogeneity/heterogeneity, premorbid individual differences, etc.) and to establish solid foundations for the interpretation of behavioural dissociations and associations. We conclude by suggesting that, alongside other neuroscience techniques, case-series cognitive neuropsychology provides a crucial contribution to the future of clinical and cognitive neuroscience.