Please cite this article in press as: Reverberi, C., et al. Cortical bases of elementary deductive reasoning: Inference, memory, and metadeduction. Neuropsychologia (2009), doi:10.1016/j.neuropsychologia.2009.01.004 ARTICLE IN PRESS G Model NSY-3173; No. of Pages 10 Neuropsychologia xxx (2009) xxx–xxx Contents lists available at ScienceDirect Neuropsychologia journal homepage: www.elsevier.com/locate/neuropsychologia Cortical bases of elementary deductive reasoning: Inference, memory, and metadeduction Carlo Reverberi a,b,∗ , Tim Shallice c,d , Serena D’Agostini e , Miran Skrap e , Luca L. Bonatti f a Bernstein Centre for Computational Neuroscience, Charité-Universitätsmedizin, Berlin, Germany b Department of Psychology, Università Milano - Bicocca, Milano, Italy c Cognitive Neuroscience Sector, SISSA, Trieste, Italy d Institute of Cognitive Neuroscience, University College, London, UK e S. Maria della Misericordia Hospital, Udine, Italy f ICREA, Universitat Pompeu Fabra, Barcelona, Spain article info Article history: Received 19 May 2008 Received in revised form 3 December 2008 Accepted 2 January 2009 Available online xxx Keywords: Executive functions Frontal lobes Logic Rules Learning Monitoring Focal brain lesions Group study abstract Elementary deduction is the ability of unreflectively drawing conclusions from explicit or implicit premises, on the basis of their logical forms. This ability is involved in many aspects of human cognition and interactions. To date, limited evidence exists on its cortical bases. We propose a model of elementary deduction in which logical inferences, memory, and meta-logical control are separable subcomponents. We explore deficits in patients with left, medial and right frontal lesions, by both studying patients’ deductive abilities and providing measures of their meta-logical sensitivity for proof difficulty. We show that lesions to left lateral and medial frontal cortex impair abilities at solving elementary deductive prob- lems, but not so lesions to right frontal cortex. Furthermore, we show that memory deficits differentially affect patients according to the locus of the lesion. Left lateral patients with working memory deficits had defective deductive abilities, but not so left lateral patients with spared working memory. In contrast, in medial patients both deductive and meta-deductive abilities were affected regardless of the presence of memory deficits. Overall, the results are compatible with a componential view of elementary deduction, and call for the elaboration of more fine-grained models of deductive abilities. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction Being able to grasp the deductive relations among sentences or thoughts is a fundamental cognitive ability. If you want to go to a movie and your friend says that if it rains she will not come, and then if it does rain, you will not wait for her. Successful exchanges of information among people, or planning of novel action sequences, require the ability to carry out such deductive inferences: our every- day mental life is densely populated by them. Deductive reasoning is often much more complex. It is involved in mathematics, formal logic, categorization, and scientific hypoth- esis testing and confirmation. Yet, while most people will never engage in sophisticated logico-mathematical reasoning in their life, the kind of everyday reasoning we exemplified above is arguably universal. As basic deductive steps are also involved in word learn- ing (Halberda, 2003), elementary reasoning is also likely to appear early in development. By contrast, most mathematical or sophisti- cated logical reasoning requires years of training and appears late ∗ Corresponding author at: Bernstein Center for Computational Neuroscience, Charité-Universitätsmedizin, Berlin, Philippstr. 13, House 6, 10115 Berlin, Germany. E-mail address: carlo.reverberi@bccn-berlin.de (C. Reverberi). in life. Different levels of performance also support the contrast between the two types of deductive abilities. While humans solve simple deductive problems involved in everyday reasoning almost flawlessly (e.g. Braine, Reiser, & Rumain, 1984), once they go beyond this level of elementary reasoning errors abound. The relations between early basic reasoning abilities and the more sophisticated ones, such as explicit logico-deductive or mathematical reasoning, are unclear. However, what is apparent is that deductive reason- ing is a multi-faced phenomenon, not necessarily involving only a single psychological mechanism. In this article, we will concentrate on the basis of elementary reasoning abilities, that is, the deductive abilities that every human being possesses and deploys in everyday exchanges of information. An elementary level of deductive inference is presupposed by both main theories on human deduction – mental models and mental logic – along with more sophisticated reasoning abilities. According to mental logic theory, reasoning involves the construc- tion of short mental proofs, built by means of a set of rules and procedures for their application. According to one of the most devel- oped version of this theory (e.g., Braine & O’Brien, 1998a), reasoners possess rules in natural deduction form that govern the introduc- tion or elimination of connectives and quantifiers. A procedure for the application of those rules (called Direct Reasoning Routine, 0028-3932/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.neuropsychologia.2009.01.004