Executive Functioning

History of Executive Functioning

[Page 604]The historical knowledge of EF skills and, in particular, the prefrontal cortex of the brain is relatively new when compared with knowledge of other parts of the brain. Of the four major lobes (i.e., temporal, parietal, occipital, and frontal), the frontal lobes, including the prefrontal cortex (the largest portion of the frontal lobes), were believed to be the most enigmatic and difficult to study. For decades, scientists were unsure and in disagreement about what the frontal lobes of the brain actually did. Some believed that the frontal lobes were not responsible for much at all, whereas others believed they were responsible for abstract thought alone. This discrepancy arose from the lack of consistency in the presentation of people with frontal lobe injuries. Over time, it became more apparent that the frontal lobes were responsible for a heterogeneous yet significant amount of functions that controlled higher order regulatory processes. Given that EF skills are required for the smooth operation and governance of a person, damage to the frontal lobes can result in dysregulation, poor decision making, and maladaptive behavior. This point was highlighted in the historical case of Phineas Gage. Gage was a railroad worker in 1848 who received a brain injury to the frontal lobes after an iron rod was driven through the front part of his skull. Prior to his injury, Gage was described as a model railroad worker and a likeable, well-mannered individual. After his injury, Gage had significant difficulty inhibiting his behavior, was prone to violent rages, and could not maintain appropriate social relationships. It is now clear that Gage suffered an extreme injury to the left frontal lobe of his brain, which resulted in significant cognitive, emotional, and behavioral changes in his personality.

It was through case examples of executive dysfunction like that of Gage that the importance of the role of EF skills has become clear. As a result, a greater understanding of how the frontal lobes contribute to an individual’s function has developed. All humans are born with EF skills; however, it is the maturation of the frontal lobes over time that allows the EF skills to become more sophisticated. Information from infant studies has shown that even babies as young as 8 to 12 months have developed the ability to inhibit a response. Throughout the course of child development, researchers have documented a significant jump in the efficiency of executive functions at specific ages, including 5 years, 7 years, 12 years, and 16 years. The studies of adolescents and young adults have shown repeatedly that EF skills are still developing well into late adolescence and young adulthood with the frontal lobes becoming fully developed by an individual’s mid-20s.

...