Is the size of the corpus callosum associated with in-terhemispheric connectivity and/or with hemispheric specialization? Some studies assume group differences in corpus callosum connectivity or behavioral asymmetry and seek morphometric confirmation in the corpus callosum. This is especially common with sex and handedness differences. While there is a consensus that handedness differences in hemispheric specialization are real, with left-handers showing decreased asymmetry and more bilateral functional representation, there is less information about handedness effects in callosal connectivity. The consensus is much less clear in the case of sex differences. While it is true that males are more likely to show lateral differentiation (interaction with lateral-ized sensory field in a behavioral laterality experiment) than females (Zaidel et al., 1995), they are not always more lateralized. Other studies find group differences in callosum morphometry and conclude that the groups differ in hemispheric specialization and/or callosal connectivity. This iterative mutual bootstrapping dance between group differences in behavioral asymmetries and in regional callosum morphometry is a valid scientific maneuver as long as we are aware of it.
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