Michiel van Lambalgen (Amsterdam) gives a talk at the MCMP Colloquium (10 Nov, 2011) titled "Logic or probability? An ERP study on defeasible reasoning". Abstract: Currently there is a vociferous debate over the question, whether actual human non-monotonic reasoning is best captured by a non-monotonic logic, or by probability theory. We take as concrete example the 'suppression task' in which supplementary information may lead to the withdrawal of an earlier conclusion from a modus ponens argument. We present logical and probabilistic models of this phenomenon and discuss the impact of recent EEG data on the validity of these models.