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The brain has two hemispheres that largely mirror each other in structure and function but also demonstrate some specialization or lateralization (Hugdahl & Westerhausen, 2010). For instance, language functions are located in the left hemisphere for most people, whereas complex visual processing tends to occur in the right one. The hemispheres are separated by the corpus callosum, which is a dense network of fibers that allows for communication between the hemispheres. When scientists have separated the hemispheres of certain patients with epilepsy by cutting the corpus callosum, the patients’ left hands literally did not know what their right hands were doing (Sperry, 1961)!

Each of the hemispheres is composed of four lobes: frontal, temporal, parietal, and occipital (see Figure 2.5). The frontal lobes—considered the seat of planning and rationality as well as being critical to gross and fine motor functioning—are, well, where you’d expect them to be, in the front part of the brain. It makes sense, then, that Gage’s ability to manage projects and to control his impulses would be compromised by the damage that his frontal lobe sustained in the explosion. The temporal lobes lie roughly behind the temples and play a central role in auditory processing, including comprehension of speech.

Figure 2.5 The Four Brain Lobes

Source: Barnes, J. (2013). Essential Biological Psychology. Thousand Oaks, SAGE.

The parietal lobes, heavily involved in the sensation of touch, sit atop the temporal lobes, extending to the top of the brain. Social neuroscientists have been particularly interested in the junction between the temporal and parietal lobes (the temporal-parietal junction or TPJ), because it is activated when a person is induced to adopt another person’s perspective (see Chapter 8) (Ruby & Decety, 2004; St. Jacques, Conway, Lowder, & Cabeza, 2011). Finally, the occipital lobes—most closely associated with vision, constitute the rear of the brain. One critical stage in the perception of faces is located here, and hence facial recognition can be hampered when it is damaged (Haxby, Hoffman, & Gobbini, 2000, 2002). Imagine how different your social interactions would be if you were unable to recognize the faces of your friends and family. Trauma to the occipital lobe can also cause what is known as blindsight, wherein your eyes register sensory input and you may be able to spatially locate objects, but you experience blindness.

Although identifying the lobes associated with certain functions can be useful at a gross level, mental processes correspond more closely with specific structures and/or regions within the lobes rather than with the lobes in their entirety. Here we will focus on a subset of brain structures that have been more heavily researched in social neuroscience and figure prominently in the explanation of social behavior (see Table 2.3). These are the prefrontal cortex, the limbic system, the insula, and thalamus and hypothalamus.

Table 2.3