From: Chris Lofting (
Date: Wed 17 May 2006 - 11:12:03 GMT

  • Next message: Chris Lofting: "RE: RS"

    Oops - left out the promised abstract re probabilities reasoning and so
    'best-fit/worst-fit' mappings:

    Cerebral Cortex, Vol. 11, No. 10, 954-965, October 2001 C 2001 Oxford University Press

    New Evidence for Distinct Right and Left Brain Systems for Deductive versus Probabilistic Reasoning Lawrence M. Parsons and Daniel Osherson1 University of Texas Health Science Center at San Antonio, San Antonio, TX and 1 Rice University, Houston, TX, USA

    Lawrence M. Parsons, Director, Cognitive Neuroscience Program, Division of Behavioral and Cognitive Sciences, Directorate for Social, Behavioral, and Economic Sciences, National Science Foundation, 4201 Wilson Boulevard, Arlington, VA 22230, USA.

    Deductive and probabilistic reasoning are central to cognition but the functional neuroanatomy underlying them is poorly understood. The present study contrasted these two kinds of reasoning via positron emission tomography. Relying on changes in instruction and psychological 'set', deductive versus probabilistic reasoning was induced using identical stimuli. The stimuli were arguments in propositional calculus not readily solved via mental diagrams. Probabilistic reasoning activated mostly left brain areas whereas deductive activated mostly right. Deduction activated areas near right brain homologues of left language areas in middle temporal lobe, inferior frontal cortex and basal ganglia, as well as right amygdala, but not spatial-visual areas. Right hemisphere activations in the deduction task cannot be explained by spill-over from overtaxed, left language areas. Probabilistic reasoning was mostly associated with left hemispheric areas in inferior frontal, posterior cingulate, parahippocampal, medial temporal, and superior and medial prefrontal cortices. The foregoing regions are implicated in recalling and evaluating a range of world knowledge, operations required during probabilistic thought. The findings confirm that deduction and induction are distinct processes, consistent with psychological theories enforcing their partial separation. The results also suggest that, except for statement decoding, deduction is largely independent of language, and that some forms of logical thinking are non-diagrammatic.


    Oaksford, M., and Chater, N., (2001) "The probabilistic approach to human reasoning" IN Trends in Cognitive Sciences Vol 5. No8 August 2001: 349-357

    (published PRIOR to the above) From the intro:

    "In a standard reasoning task, performance is compared with the inferences people should make according to logic, so a judgement can be made on the rationality of people's reasoning. It has been found that people make large and systematic (i.e. non-random) errors, which suggests that humans might be irrational. However, the probabilistic approach argues against this interpretation" (p349)


    =============================================================== This was distributed via the memetics list associated with the Journal of Memetics - Evolutionary Models of Information Transmission For information about the journal and the list (e.g. unsubscribing) see:

    This archive was generated by hypermail 2.1.5 : Wed 17 May 2006 - 11:34:36 GMT