Divergent Thinking Styles of the Hemispheres: How Syllogisms Are Solved during Transitory Hemisphere Suppression

An evaluation of dual-process theories of reasoning

“…Goel's (Goel, Buchel, Frith, & Dolan, 2000;Goel & Dolan, 2001;Goel, Gold, Kapur, & Houle, 1997) neuroimaging studies lend further support to Deglin and Kinsbourne's (1996) claims. Normal participants were asked to assess the validity of contentful and abstract syllogisms under time pressure conditions.…”

“…In addition, Ford found that verbal protocols, along with the diagrams that participants constructed, indicated the types of cognitive styles (i.e., visual or verbal representations of premises) that they developed to solve syllogisms. Deglin and Kinsbourne (1996) examined neurologically impaired patients' (i.e., schizophrenics and manic depressives) performance on contentful syllogisms. Each patient was tested three times, once before ECT (electroconvulsive therapy), then once with ECT-induced RH and LH suppression.…”

“…There is, however, some disagreement as to which hemispheric region is associated with particular forms of reasoning. For example, clinical studies that examine patients with LH and RH damage (Golding, 1981) or that induce suppression of these regions (Deglin & Kinsbourne, 1996) suggest that the LH is dominant in abstract deductive reasoning and that the RH is associated with content-based reasoning (e.g., Goel et al, 2000) and probabilistic inferencing (e.g., Wharton & Grafman, 1998). Studies directly comparing probabilistic and deductive reasoning have found that there is a logic-specific network in both the LH and RH and that probabilistic reasoning activated mostly LH regions (Osherson et al, 1998;Parsons & Osherson, 2001), which conflicts with other attempts to localize distinct reasoning mechanisms.…”

“…System 1, which is essentially pragmatic, is based on prior experiences, beliefs, and background knowledge and achieves goals reliably and efficiently without necessarily accompanying awareness. It is characterized as implicit, associative, fast, and highly robust, and it is spared by both aging (Gilinsky & Judd, 1994) and neurological damage (e.g., Deglin & Kinsbourne, 1996). System 2 is explicit, sequential, controllable, and makes high demands of working memory.…”

Development of intuitive rules: Evaluating the application of the dual-system framework to understanding children’s intuitive reasoning

“…Individuals with poorer cognitive ability will perform poorly on these tasks, because the secondary system is unable to inhibit erroneous responses generated by the primary system. Stanovich and West (2000) and Evans and Over (1996) also proposed that because the primary system is robust, it is spared by aging (Gilinsky & Judd, 1994) and neurological damage (e.g., Deglin & Kinsbourne, 1996). Because of this, they predicted that inverted U-shaped development occurs, in which the development of executive functions tracks improvements in performance in reasoning tasks but declines as executive functions become impaired through aging.…”