One of the greatest scientific mysteries is how the human mind/brain functions. For example, how does a young child control his or her temper? How does a child manage to sit still in school and pay attention to what the teacher is saying? How do we decide what career to pursue, make plans to obtain our academic goals and to pursue them despite often severe difficulties? How do we manage the intricacies of human relationships including intimate ones? These are just a few of the many life tasks involving what neuropsychologists refer to as executive function.

Briefly, executive function is the set of cognitive processes which enables us to become aware of our needs and desires, and to create ways to attain them.

Executive function is a term perhaps unfamiliar to many mental health professionals but it is extremely important because it could be considered the brain function that sets us apart from other animals and hence the defining characteristic of human beings. Even the technical name of our species, homo sapiens, which means "knowing man" points to its importance.

To a much greater degree than other animals including our closest primate species, humans evolved the capacity to formulate goals, develop complex strategies to attain them and exert conscious, and many times effortful action to attain these goals. This is executive function and modern civilization could not have existed without it. Yet we know so little about how the human mind accomplishes these executive functions.

Problems in defining and measuring executive functioning

Despite its importance, the term executive function is difficult to define in a technically precise way. Barkley in Chapter 1 of "Executive Functions" reviews the history with its origin in a study conducted over 100 years ago on the behavioral effects of damage to the frontal lobes of the brain. Since then most neuropsychologists have included frontal lobe damage in their definitions. However the definitions changed as research methods improved and knowledge accumulated about the term. And as this happened a sometimes confusing variety of definitions arose.

Barkley in his book begins by defining it as self-regulation but gradually in the following pages of the book provides an increasingly deeper and broader conception based on his extensive neuropsychological research. Unlike most previous attempts at conceptualizing the term, his includes an evolutionary and developmental perspective. He makes it a point to not adhere strictly just to the old brain lesion-behavioral effects approach. Barkley in unique in thinking of executive function as part of the "extended phenotype" of humans as is explicated in the following section.

What is extended phenotype and what are the advantages to using the concept?

For the sake of simplicity, phenotype is defined here as the structural and functional characteristics of an organism which are produced from its genes. In actuality the concept has undergone modifications since first proposed over a century ago and now is often thought to include the products of behaviour eg a bird's nest or a spider's web. Dawkins (1982) further expanded on the latter aspect and called it the extended phenotype.

There are several important advantages to using this concept of extended phenotype. The first reason is revealed by Barkley's choice of title for his Chapter 2 "The Extended Phenotype: A foundation for modelling executive functioning". The use of extended phenotype logically leads to a much more complex and complete model of executive function.

Secondly, Barkley's wise use of the concept of the "extended phenotype" (instead of the widely known and applied "general systems" approach) facilitated his modelling executive function hierarchically from the genetic level, to the conventional phenotypic level (the organism bounded by its physical surface (skin), to the extended phenotypic level which involves the organism interacting with the environment including objects created by this interaction. Thirdly, the concept of extended phenotype along with an evolutionary perspective emphasizes the importance of environmental factors both in the evolution of executive function and in its proper assessment by neuropsychologists and clinicians.

Brief Outline of Barkley’s Model of Executive Function as an Extended Phenotype

Barkley's Hierarchy of Levels of Executive Function

Barkley's use of extended phenotype along with an evolutionary developmental approach logically leads to a hierarchical systemization of executive functioning into 6 levels of executive function of increasing levels of complexity and extension outwards from the individual (conventional phenotype). The names of each level along with a simplified description are provided below:

Pre-executive level (unconscious involuntary actions including reflexes, homeostatic functions and conditioned reflexes; Barkley also includes here "primary neuropsychological processes such as attention, memory, spatial and motor functions, primary emotions and motivations"; Barkley does not consider this level as truly executive since it is not conscious, voluntary and effortful, characteristics which he assumes essential).

(unconscious involuntary actions including reflexes, homeostatic functions and conditioned reflexes; Barkley also includes here "primary neuropsychological processes such as attention, memory, spatial and motor functions, primary emotions and motivations"; Barkley does not consider this level as truly executive since it is not conscious, voluntary and effortful, characteristics which he assumes essential). Instrumental-self-directed level (internalized mental processes: e.g. internal self-talk eg emotional self-regulation)

(internalized mental processes: e.g. internal self-talk eg emotional self-regulation) Methodical-self-reliant level (behaviours one could generally carry out by oneself)

(behaviours one could generally carry out by oneself) Tactical-reciprocal level (social behaviours ie interacting with others)

(social behaviours ie interacting with others) Strategic-cooperative level (more complex social interactions)

(more complex social interactions) Principled-mutualistic level (the broadest social ecology in which "each individual strives to look out for others' long-term self-interest, provided those others do the same.")

6 Types of Executive Function

In Chapter 4, are listed the six types of executive functions used specifically at the Instrumental-Self-Directed Level i.e. actions by the self which are directed at the self and in such a way that the individual is more successful in attaining a goal. These types of executive function are:

Attention : paying attention to the self by 1. specifically monitoring discrepancy between distant desired state and current state and 2. monitoring usefulness of ongoing strategies to attain desired goal

: paying attention to the self by 1. specifically monitoring discrepancy between distant desired state and current state and 2. monitoring usefulness of ongoing strategies to attain desired goal Inhibition : the capacity to stop an action (impulse) based on awareness of relevant information, and taking corrective action based on information gained through self-attention

: the capacity to stop an action (impulse) based on awareness of relevant information, and taking corrective action based on information gained through self-attention Self-directed sensory-motor action: Involves non-verbal working memory, imagination including especially visualizing)

action: Involves non-verbal working memory, imagination including especially visualizing) Self-directed speech : speech (public or private) to self; involves verbal working memory, especially mental verbalization = thinking).

: speech (public or private) to self; involves verbal working memory, especially mental verbalization = thinking). Self-directed appraisal (emotion and motivation): emotional effects of actions

(emotion and motivation): emotional effects of actions self-directed play: innovation and problem solving

Some difficulties with Barkley's approach

Three possible criticisms of Barkley's approach are:

Although implicitly acknowledging the importance of the self (note how many times the word self is mentioned in the above outline) and discussing how it is missing from other researchers' formulations of executive function, Barkley does not provide an explicit description of how the self is involved in executive function. At the bottom of page 58 Barkley writes "It is important to note here that evolution does not proceed for socialistic or collectivist motives but from self-interested one (Dawkins, 2006)". Dawkins in the introduction to the 30th anniversary edition recants his use of the word selfish and writes that it referred only to the unit selected by natural selection. At the bottom of page 58 Barkley writes "It is important to note here that evolution does not proceed for socialistic or collectivist motives but from self-interested ones" with a reference to Dawkins' "The Selfish Gene". Obviously there can be no "self" let alone "self-interest" at the genetic level. From developmental psychological research on the self and from the concept of the biological medial self system (Northoff and Panksepp (2008), Panksepp and Northoff (2009)), it would seem that the self is a complex biological-psychological-sociological system which develops in a specific context. One might consider the concept of the self as analogous or identical with executive function--extended phenotype discussed by Barkley. Barkley's model seems to not include the well known and important capacity to shift between the two fundamental states of brain function i.e. fast automatic mode versus slower reflective mode as described in Nobel prize winner Kahneman's book "Thinking Fast and Slow" (2011). Only "slow thinking" would fit Barkley's requirement that executive function be conscious, voluntary and effortful. And yet as Kahneman and many others have shown most decision making occurs unconsciously. A related problem arises from the work of Miyake et al (2000) who concluded that there are three basic types of executive function: working memory operations, inhibition, and mental set shifting. Barkley's model seems to lack the capacity for shifting mental sets although the executive function of inhibition along with decision making may allow set shifting. Barkley in Chapter 4 proposes that executive functioning first emerges at the Instrumental self-directed level seemingly holus bolus suggesting a jump from the pre-executive level to the executive levels without any intervening stages. This is contrary to the way evolution works.

Why This Book Is Useful for Mental Health Professionals

Chapter 10 is entitled "Implications for Assessment and Clinical Management of Deficits in Executive Functioning". After digesting this chapter and its important clinical implications, the reader is unlikely to ever intervene with a patient in exactly the same way. One is likely to become sensitized to the role of executive function difficulties in the vast majority of people who come for psychotherapy. The reader is also likely to become much more aware of the complex interaction between the client’s environment and the client's executive function limitations and how consideration of such interactions can lead to creative new interventions.

Barkley provides a useful example of how to take advantage of such interactions in a section entitled "Intervene at the Most Disrupted Level" (p. 208). He suggests that the individual be helped to reorganize their external environment to compensate for their executive function problems. He mentions the use of "artificial devices such as digital memory recorders, computers, personal data assistants, or cell phones to which periodic prompts and reminders are sent, and other such environmental prostheses."

Also in this closing chapter, Barkley suggests (p. 206) in a section entitled "Approach executive function deficits as a chronic condition" that "diabetes is an analogous condition to many forms of executive function deficits." He is proposing that the client and those he or she interacts with, including the therapist, must appreciate that there is no permanent cure although there are many treatments that can greatly assist the client including "taking daily doses of medication and changing settings, task, and lifestyles".

Concluding remarks

"Executive Functions" is not a popularization for the general reader and even specialists in this area may find it difficult reading. It is difficult for several reasons: firstly because of the subject matter: the human mind may be the most complex object in the universe: secondly because executive function has not been clearly; thirdly because Barkley refers to many approaches which are perhaps foreign to the reader e.g. evolutionary. In this regard, it may be useful to read simultaneously another of his books "Taking Charge of Adult ADHD" (2010) which was written for the general public and provides a simpler description of many concepts.

Barkley has provided the most up-to-date conceptualization of the nature of executive function. This book has changed and vastly expanded my perspective on how the mind functions. I am certain that it will help future researchers develop a model of how the brain functions. Also from a more practical point of view, it will help mental health workers understand how the brain functions and from this improved understanding they will be better able to help clients who have executive dysfunction..

The reader of "Executive Functions" may conclude that Russell Barkley is attempting to sum up and integrate his vast store of psychological and evolutionary knowledge and wisdom. If so, Barkley has done an admirable job and produced a book well worth reading and indeed studying. He is to be commended for giving us an inspired and comprehensive model not only of executive function but also of how the human mind works in general. This book will undoubtedly be useful to future investigators of that great mystery, the human mind.

Image Credited to MoonyWolf of Deviantart

References

Barkley R. A. (with Benton, C.M.). (2010). Taking Charge of Adult ADHD. Guillford Press, New York, NY, USA.

Barkley R. A. (2012). Executive Functions. Guillford Press, New York, NY, USA.

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

Dawkins, R. (2006). The Selfish Gene. Oxford University Press, New York, NY.

Kahneman, D. (2011). Thinking Fast and Slow. Farrar, Straus and Giroux, NY.

Miyake, A., Friedman, N., Emerson, M., Witzki, A., Howerter, A., & Wager, T. (2000). The unity and diversity of executive functions and their contributions to complex "frontal lobe" tasks: A latent variable analysis. Cognitive Psychology ,41,49-1000.

Northoff, G., & Panksepp, J. (2008). The trans-species concept of self and the subcortical-cortical midline system. Trends in Cognitive Sciences, 12(7), 259-264.

Panksepp, J., & Northoff, G. (2009). The trans-species core SELF: The emergence of active cultural and neuro-ecological agents through self-related processing within subcortical-cortical midline networks. Consciousness and Cognition: An International Journal, 18(1), 193-215.