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
Prefrontal Cortex
Sometimes called the executive of the nervous system, the prefrontal cortex is associated with selecting and guiding behavior. It receives information from many parts of the brain and integrates these when setting goals, planning, and directing behavior (Miller & Cohen, 2001). Remember how the injury to Gage’s prefrontal cortex prevented him from setting goals and controlling his behavior. Our ability to take environmental cues and conditions into account when deciding how to behave is dependent on the prefrontal cortex (Miller & Cohen, 2001). For instance, when do you decide to scratch or ignore an itch in a private part of your body? Obviously, context matters. Hopefully, you will ignore it when you are speaking in public, but you may deal with it immediately when you are home alone in your living room. This sensitivity to external cues is particularly important for social behavior because it so often is (or should be!) responsive to context.
Limbic System
The limbic system is a set of connected structures that are central to the experience and regulation of emotions, motivation (including eating, drinking, and sex), and memory. The limbic structures most relevant to social psychology are the amygdala and hippocampus. (See Figure 2.6.)
Amygdala. An almond-shaped structure that is physically connected to the ends of the basal ganglia and is closely associated with the detection of and response to threat. Damage to the amygdala appears to inhibit people from experiencing an appropriate fear response to potentially threatening stimuli—such as a receiving a painful shock (Olsson & Phelps, 2004). For example, if a person is unable to feel fear when he notices that another man is becoming very angry at him, then he is much more likely to be vulnerable to potential aggression.
Hippocampus. This structure plays a crucial role in memory formation and recall and, together with the amygdala, creates emotional memories. The hippocampus is a key component of the controlled processing system that we discuss in detail in Chapter 3 (Lieberman, 2007b). The hippocampus is also key to spatial awareness and navigation, as demonstrated by the fact that the right side is enlarged in the brains of London taxi drivers (Maguire & Gadian, 2000). However, the hippocampus-taxi driver relationship is correlational, and therefore it is unclear how the two are causally connected, if at all. Individuals who are unable to create long-term memories often have damage to the hippocampus.
Figure 2.6 The Limbic System
Source: Kuther, T. L. (2017). Lifespan Development: Lives in Context. Thousand Oaks, CA: SAGE.
Insula
The insula is connected to the olfactory bulbs and is involved in the reaction to smells, such as the disgusting aroma of spoiled meat and unpleasant odors stemming from other people. The olfactory bulbs are part of the only sensory system in which stimuli from the external world are piped directly to the brain (including the amygdala) without first passing through the thalamus. As a result, smells such as those indicating spoiled meat and the presence of predators or other people have a particularly powerful influence on behavior. The insula has also been associated with moral disgust, and there is evidence that the brain responds to moral and physical disgust in similar ways (see Research Box 2.1) (Tybur, Lieberman, Kurzban, & DeScioli, 2013).
Thalamus and Hypothalamus
Sensory information (with the exception of smell) is transmitted to the thalamus, which processes it and then sends to other parts of the brain, including the amygdala. The hypothalamus—through its effects on the release of hormones by the pituitary gland—seems to have a role in virtually all aspects of behavior, such as sexuality, sleeping, and feeding, and is also involved in the regulation of bodily temperature. These structures are associated with the experience and expression of emotion and with the fight-or-flight response.
Think Again!
1 How does injury to the prefrontal cortex affect behavior?
2 What is the function of the amygdala?
3 Imagine a person’s insula were severely damaged and she could no longer experience disgust. What would the consequences be?
Research Box 2.1
Moral Disgust and the Insula Hypothesis: The Perception of Disgust
Hypothesis: The perception of disgust responses in the facial expressions of others would be associated with activation of the insula but not the amygdala.
Research Method: Across four experiments, seven participants viewed photos of male and female facial expressions reflecting disgust, fear, or no emotion. They believed that the purpose of the study was to identify the sex of the person in the photo, when in fact the researchers were interested in their perception of and response to facial expressions. The experiments were completed while the participants were undergoing fMRI scanning.
Results: As expected, perception of disgust expressions led to greater
