Moral Development and the Brain

Moral reasoning is the ability a person has to reason in and through social, ethical, and emotional situations. One component of moral reasoning is moral behavior, which is the intentional and voluntary acting in a prosocial manner (Walker, 2004). Moral behavior and reasoning are the foundation for “many human social and cultural institutions such as family structures, legal and political government systems that affect the lives of virtually every person” (Eslinger, Flaherty-Craig, & Benton, 2004, p. 100). Often situations in life are morally ambiguous and involve a choice between two actions that both have consequences that may or may not be in opposition to each other. Some researchers, such as Lawrence Kohlberg, believe that people will reason through these situations at varying levels or stages, with some in a very concrete and egotistic manner and others in an abstract and universal manner.

Lawrence Kohlberg was the first researcher to come up with a major testable theory of moral development. He formulated six stages of development, with most adults reaching stage four, a few five, and very few stage six. The first two stages are at the pre-conventional level (typically self-centered and concrete reasoning), stages three and four are at the conventional level (recognition of social norms and laws), and the last two stages at the post-conventional level (recognition of universal rights and responsibilities). While Kohlberg’s theory of moral development is a stage model, the progression through the stages is not necessarily viewed as invariant. This means that people reach them at different rates and do not always reason at a particular stage with any given dilemma. There is significant variability within and between people in moral reasoning abilities. Most research focuses on between-person variability.

While there are multiple ways to test moral reasoning, one way is to present vignettes and ask for a choice in response to the situation. Researchers present these short ethical dilemmas and force the participants to make a choice between two actions; the participants then also often describe why they made that choice. For example, participants might have to choose between killing one person to save five others or, letting the five people die because they cannot kill the one. A dilemma such as this helps researchers understand why people make the choices they do in socially and ethically-charged situations.

One measure designed to assess moral development is the Defining Issues Test (DIT) which was developed by Rest (1979) and revised (as the DIT2) in 1999 (Rest, Narvaez, Thoma, & Bebeau, 1999). The DIT is a self-report and objective measure of moral reasoning based upon Kohlberg’s theory of moral development. It is the most common measure used in moral development research (Walker, 2004). King and Mayhew (2002) reviewed the use of the test in higher education. They demonstrated that people with more education show higher levels of moral judgment than do those with less education, even matched for age (which is a predictor of moral reasoning). Cottone, Drucker, and Javier (2007) found that people with higher executive functioning scores had higher rates of post-conventional reasoning on the DIT2.

Some researchers focus on the relationship between underlying cognitive schemas and moral reasoning (e.g., Narvaez & Bock, 2002) while others focus on how emotions relate to moral behaviors (e.g., Damasio, 1994; Koenigs et al., 2007). Researchers have looked at different factors that at least partially explain the variance in differing moral reasoning. Age and education both relate to moral reasoning, with adults and those who have more education reasoning at higher stages on average than adolescents and less educated people (Proios & Doganis, 2006). Personality traits also relate to moral reasoning (Benware, 2002). Additionally, researchers have started studying how moral behavior relates to biological factors.

An ever-expanding body of research focuses on how the brain relates to moral behaviors (Koenigs et al., 2007). The first such case in recorded medical history is the case of John Gage. Gage was a railroad foreman – intelligent, even-tempered, and reasonable. After a tragic accident, where a tamping rod passed through his skull and brain, Gage was left a changed man. His language and intelligence appeared intact but he had impaired reasoning abilities. He had a short temper, could not hold a job, and often acted as if he had weakened morals (Damasio, 1994). Later research and computer reconstruction of the tamping rod, skull, and brain revealed that the rod passed only through Gage’s prefrontal cortex, sparing language and motor abilities (Damasio, Grabowski, Frank, Galaburda, & Damasio, 1994).

As a result of this dissociation, or separation, between functions (e.g., language and social reasoning), researchers learned that brain functions are, to an extent, localized and modular. In other words, damage to specific areas of the brain can impair specific functions without affecting other functions. Damage to the prefrontal cortex in humans results in impaired social and moral behavior (Anderson, Bechara, Damasio, Tranel, & Damasio, 1999) as well as general moral judgment (King & Mayhew, 2002; Koenigs et al., 2007). Emotional regulation, which is also important to social and moral reasoning, is impaired with prefrontal cortex damage (Damasio, 1994). Executive function, the general ability that people have to shift-set, plan, and execute behavior is also impaired by damage to the prefrontal cortex (Sapolsky, 2004). However, people with focal prefrontal cortex damage usually have intact intelligence, verbal abilities, and memory (Eslinger et al., 2004).

The brains of normal infants develop rapidly pre- and post-natally. The last areas of the brain to finish development (i.e., growth and myelination) are the frontal lobes, specifically the prefrontal cortex. The overall volume of the brain does not increase dramatically from age 5 onward but various substructures and areas change with age. Throughout adolescence, cortical thickness decreases while underlying white matter volume increases, presumably as myelination and neuronal connectivity develops (Giedd et al., 1999; Whitford et al., 2007). This change occurs most dramatically in the prefrontal cortices of early adolescents (around age 14). In addition to volumetric and morphologic studies, researchers also have used diffusion tensor imaging (DTI) to measure the integrity and developmental differences of frontal lobe white matter between adolescents and adults (Giorgio et al., 2007).

DTI is sensitive to the diffusion of water in the brain. Water molecules move in a more directional manner (anisotropy) parallel to the length of axons in the brain. Brain areas with fewer axons (i.e., less white matter or more non-myelinated white matter), such as in the gray matter, have more random water molecule movement and thus lower signal in DTI. DTI has been shown to be a useful in vivo method to measure the integrity (usually myelination in young and healthy developing brains) of the white matter in brains. White matter changes as people age, with myelination of the frontal lobes increasing into the third decade of life (Giorgio et al., 2007). These changes in the structure of the brain correlate with impulse control, emotional control, and other cognitive abilities such as working memory (Silveri et al., 2006).


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