As science inevitably evolves, ideas once considered established are subject to debate, and this is the case with thinking regarding brain lateralization. Since the mid-20th century, evidence indicated that the differing brain hemispheres dominated specific functioning, and it became largely accepted that “right brain” individuals are more intuitive and creative, with “left brain” types tending more to objectivity and analytical thinking. While modern studies examine the legitimacy of this, there is nonetheless good reason to believe that language is largely controlled and understood by the left hemisphere, in which the cerebral language centers reside. For example, extensive research supports that human infants are more responsive to communication transmitted to the right ear, which translates to left brain response as more active (Molfese, Segalowitz, 1988, p. 73). This left brain dominance is also supported by a further analytical dominance; research in fact suggests that language as predominantly a function of the left brain hemisphere correlates to that sphere’s role in mathematical reasoning, as both language and arithmetic processes then occur primarily in the left region (Pinel, Deheane, 2010, p. 58). If modern studies go to understanding the more interactive and cooperative processes of the hemispheres, there is nonetheless strong evidence going to language as a left brain function.
Not unexpectedly, then, injury to the left side of the brain consistently damages speech and comprehension abilities. In a study of young children suffering mild to moderate traumatic brain injury (TBI), those with injuries to the left hemisphere evinced consistently greater language impairment. The evidence suggests also that this disability triggers left brain resources by which communication may occur in other ways, as the children studied “adapted” to their impairment: “The use of gestures to initiate social interaction may indicate a developmental lag or deficit in the continued reliance on gestures to support verbal communication” (Ewing-Cobbs et al, 2012, p. 258). In other words, physical functions reflexively begin to take on communication behaviors when the cognitive processes are hampered.
- Ewing-Cobbs, L., Prasad, M. R., Swank, P., Kramer, L., Mendez, D., Treble, A., … & Bachevalier, J. (2012). Social communication in young children with traumatic brain injury: Relations with corpus callosum morphometry. International Journal of Developmental Neuroscience, 30(3), 247-254.
- Molfese, D. L., & Segalowitz, S. J. (1988). Brain Lateralization in Children: Developmental Implications. New York, NY: Guilford Press.
- Pinel, P., & Dehaene, S. (2010). Beyond hemispheric dominance: brain regions underlying the joint lateralization of language and arithmetic to the left