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Attention Deficit Disorder Association

Executive Functions: What They Are, How They Work, and Why They Evolved, by Russell A. Barkley,
A Book Review

By J. Russell Ramsay, Ph.D.

Attention-Deficit/Hyperactivity Disorder (ADHD) is increasingly recognized as a developmental disorder of impaired executive functions. Rather than trying to seek an "attention” deficit in an adult, or attempting to separate "hyperactive” behavior from "typical” childhood activity, the executive function (EF) model provides a domain of behaviors that lend themselves to observation and assessment, more so than do the iconic but hard-to-define symptoms ensconced in the name of the disorder.

In his new book, "Executive Functions: What They Are, How They Work, and Why They Evolved,” Dr. Russell Barkley takes on the challenge of offering a cogent definition of the EFs, their relevance for human functioning, and an evolutionary perspective on why EFs came about at all. Although obviously stemming from and synthesizing Dr. Barkley’s lifetime of research into the effects of ADHD across a person’s lifespan, this book focuses on the existence and workings of EFs in human nature and their relevance for a wide range of topics beyond ADHD. This is not a clinical workbook or self-help guide, as was Dr. Barkley’s previous book, "Taking Charge of Adult ADHD” That being said, his review of the EFs does nothing but provide further support for the validity and seriousness of the diagnosis and need for treatments for ADHD.

After laying out the questions to be addressed in the book, namely those making up the book’s subtitle, Barkley reviews the multitude of EF definitions that have been given over the years and the limitations we have faced because of how EFs were previously understood and assessed. Barkley transcends these definitional and clinical shortcomings by adopting an extended phenotype view of the EFs. The extended phenotype is an evolutionary framework proposed by Richard Dawkins (1982) that helped explain the deep connection between genes, behavior, and the creation of artifacts that may clues to understanding the organisms that created them. For example, there are parasites that may propagate their genes by being able to be sustained longer and spread farther by host organisms than the parasites could do on their own. Summarized all too briefly, Barkley’s central thesis is that the EFs are self-regulatory behaviors that allow individuals to organize and execute plans that will improve their overall well-being in the future. Evolving as a social species, there was an overlap of the "individual” well-being of various members of a social group. This overlap of interests resulted in increasingly cooperative and mutually beneficial activities that produced larger, more complicated endeavors, such as communities, division of labor, and government, that created a selection pressure for the development of more sophisticated EFs so as to promote these complex social interactions.

The chapters in the middle of the book expand on this extended phenotype conceptualization of the EFs. Individual chapters are devoted to each zone of influence of the executive functions and their impact on human nature and societal functioning at that particular level of development. The final two chapters of the book address various disorders of the EFs, assessment, and treatment options, including discussions relevant for ADHD.

In terms of the objectives of the book, Barkley offers a definition of the EFs as "the use of self-directed actions so as to choose goals and to select, enact, and sustain actions across time toward those goals usually in the context of others, often relying on social and cultural means for the maximization of one’s longer-term welfare as the person defines that to be” (p. 176). He thoroughly reviews the basis for each element of this definition throughout the text.

The specific EF domains that have been identified for clinical assessment are: self-management across time, self-organization and problem solving; self-restraint (i.e., behavioral inhibition); self-motivation; and self-regulation of emotions (see also Barkley, 2011). The presence of these EFs has been identified as a reliable diagnostic indicator in the assessment of adult ADHD (Kessler et al., 2010). Across individual development, the EFs unfold from the Pre-Executive level (the neurological building blocks for later EFs), to the Instrumental-Self-Directed level (when the EF domains listed above emerge), to the Methodical-Self-Reliant level (goal-directed sequences of action are employed), to the Tactical-Reciprocal level (goals are met through social exchange and sharing), to the Strategic-Cooperative level (cooperation and acting in unison are used to achieve larger goals than could be achieved alone), culminating in the Extended Utilitarian level (goal-directed behaviors are guided by principles and to achieve mutually beneficial outcomes). The effects of the EFs radiate further away in time and distance from the individual with each successive level, though continuing to contribute to individual well-being and fitness for survival.

The answer to "why” EFs exist at all is associated with the increased social demands of group living, particularly groups of non-relatives with overlapping self-interests. Working together, groups of individuals can achieve more personally relevant goals than can be achieved alone. Of course, with increased cooperation (guided by individual self-interests), there is also increased opportunities for exploitation and "cheating,” which may create the need for rules, laws, and sense of morals, which could be considered social artifacts of the extended phenotype model.

Although not a book on ADHD per se, the role of the EFs is central to understanding the effects of ADHD on functioning, a view that has been put forward by Barkley, Dr. Thomas E. Brown, and many other leaders in the field. Barkley weaves his theory using evolution, the extended phenotype model, neuropsychology, psychology, etc. and illustrates the role of EFs on various facets of human nature, social institutions, and fields of study, such as economics. Professionals interested in ADHD and EFs will find a great deal of helpful background and theoretical information. The clinical applications of the model are addressed at the end of the book, though in somewhat broad strokes. Overall, this extended view of the EFs makes for a fascinating read about an important facet of human nature and will give interested readers much to ponder.

J. Russell Ramsay, Ph.D. is Co-Chair of ADDA’s Professional Advisory Board, co-director and co-founder of PENN's Adult ADHD Treatment and Research Program, and associate professor of clinical psychology at the Perelman School of Medicine. Dr. Ramsay is author of Cognitive-Behavioral Therapy for Adult ADHD: An Integrative Psychosocial and Medical Approach (Practical Clinical Guidebooks) (with Dr. Anthony Rostain) and Nonmedication Treatments for Adult ADHD: Evaluating Impact on Daily Functioning and Well-Being.


Barkley, R. A. (2011). Barkley deficits in executive functioning scale. New York: Guilford.

Dawkins, R. (1982). The extended phenotype: The long reach of the gene. New York: Oxford University Press.

Kessler, R.C., Green, J. G., Adler, L. A., Barkley, R. A., et al. (2010). Structure and diagnosis of adult attention-deficit/hyperactivity disorder: Analysis of expanded diagnostic criteria from the adult ADHD clinical diagnostic scale. Archives of General Psychiatry, 67, 1168-1178.


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