Reasoning and Problem Solving: Models

Summary, Conclusions, and FutureDirections The findings discussed in this article support thefollowing conclusions about the neural bases ofreasoning. First, deductive reasoning does not appearto recruit a unitary neural system but instead engagesdifferent brain regions based on the particularreasoning task and materials employed. Second,inductive inferences drawn from familiar categoricalsyllogisms and conditional statements engage a left-hemisphere language and knowledge network imple-mented in frontal and temporal regions. Third,problem solving generally recruits prefrontal regions,includingbilateralDLPFCandMVPFC.Fourth,causalreasoning does not engage a single neural system butinstead recruits different systems based on the causalreasoning task and the consistency of causal evidencewith background beliefs. Finally, analogical inferenceselectively recruits frontal and parietal regions, withfrontopolar cortex becoming increasingly importantas task complexity increases.The neuroscience evidence reviewed helps evaluatecurrent psychological theories. First, reasoning typi-cally recruits broadly distributed neural systems,providing evidence inconsistent with the relativelylocalized predictions of modularity theory. Possibleexceptions include the importance of certain frontalregions for problem solving (left DLPFC) and analogi-cal reasoning (frontopolar cortex). Second, the resultsdemonstratethatreasoningdoesnotsolelyrecruit left-hemisphereregionsforlanguageandrule-basedopera-tions. Instead, reasoning often engages bilateral andposterior regions beyond those implicated by amodaland mental logic theories of reasoning. Third, the pre-dominantly right-hemisphere system predicted by themental-models theory across both deduction andinduction is inconsistent with many patterns of left-hemisphere and bilateral activation observed acrossstudies. Fourth, dual-process, dual-code, and embod-ied theories are generally consistent with the reviewedfindings. These theories receive support because theypredict the presence of (1) broadly distributed neuralsystems and (2) multiple reasoning systems (e.g., asso-ciative vs. rule, language vs. knowledge). These the-ories also receive support from the many studies thatexhibiteffectsoftaskspecificityandcognitivedemand.As task conditions change, so do the neural systemsthat represent and process the relevant information.In general, reasoning tends to recruit broadlydistributed and diverse neural systems. The difficultyof establishing specific neural systems for a given typeof reasoning (e.g., deduction) strikes us as one majorchallenge for future research. Does a particular type ofreasoning consistently activate a specific neural circuitacrosswidevariationintasksandmaterials?Ifso,whatis this circuit? Another major challenge is that the mul-tifaceted nature of the neurobiological evidence andcognitive theories results in a many-to-many mapping:neural regions often serve multiple cognitive functionsthat can be mapped onto multiple cognitive theories.Sortingoutthefunctionalrolesofparticularbrainareasand their roles in psychological theories of reasoningshould be another major goal in this research area.Many other challenges also await future researchin this area. For example, do the results from thelaboratory tasks reviewed here generalize to everydayreasoning tasks? Rather than occurring in a vacuum,everyday reasoning often occurs in social situationsand is associated with emotional affect. What are theneural bases of reasoning under these conditions?How do social and emotional processes modulatereasoning? Future research should also address theimportant distinction between reasoning to a conclu-sion versus recognizing a conclusion. Because manyreal-world situations require that people generatevalid conclusions (not just recognize them), futureneuroscience research should assess the neural basesof this process. Future research should also continueto address the role of task difficulty in reasoning.Does task difficulty result in the recruitment of morebrain regions, or are the same regions activatedmore intensely? Future research should also addressthe effect of learning on the neural systems thatunderlie reasoning. Do novices and experts engagesimilar neural systems during reasoning?Finally,researchersshoulddeveloppsychologicalthe-oriesthatmotivatefine-grainedneurobiologicalpredic-tions, and should design experiments that distinguishbetweentheories,ratherthansimplyattemptingtocon-firm one. Although much progress has been made inframing the issues and establishing preliminary evi-dence, neuroscience research on reasoning is still in itsinfancy.Weanticipatemajoradvancesincomingyears.