Evaluating the empirical support for the Geschwind-Behan-Galaburda model of cerebral lateralization.

The Geschwind-Behan-Galaburda (GBG) model of cerebral lateralization provides a complex but testable theory of the origins and associates of cerebral lateralization. An overall evaluation of the model suggest that it is not well supported by empirical evidence and that in the case of several key theoretical areas, the evidence that does exist is inconsistent with the theory. In particular: the concept of "anomalous dominance" is shown to be theoretically and methodologically flawed; a meta-analysis of the relationship between handedness and immune disorders finds a marginal overall association, and while three conditions (allergies, asthma, and ulcerative colitis) do show significant associations with left-handedness, two other conditions (myasthenia gravis and arthritis) show significant negative associations with left-handedness. Finally, a review of the origins of the neural crest, and its associations, suggests there is almost no empirical support for the GBG theoretical model in this area.