Book Review

Review of Executive Functions:What They Are, How They Work, and Why

They Evolved, by Russell A. Barkley

Joseph C. Blader, PhD

Leave it to Russell Barkley, one of our field’s most ex-

pansive and nimble thinkers, to combine at least two books

into this volume of just over 200 pages of text.

The first offers a conceptualization of executive functions (EF)

intended to remedy flaws in prevailing ideas about them, which

Barkley identifies in a withering critique. The central idea he

elaborates is that EF are ‘‘self-directed actions needed to choose

goals and to create, enact, and sustain actions toward those goals’’

(p. 60). Notice the verbs in this definition – for example, choose,

create – because they signify Barkley’s real passion, reclaiming, on

behalf of the living, socially engaged, striving self, territory in

psychology now occupied by pallid, eviscerated entities such as the

‘‘central executive.’’ Barkley’s criticism of the EF field dutifully

includes concerns about the psychometric properties of current

measures, the tendency to confuse anatomical localization with a

meaningful definition (e.g., EFs are ‘‘what the frontal lobes do’’),

and weak consensus on core concepts. But he saves his most ve-

hement language to attack the reductionism of the individual to, in

essence, software: ‘‘Instead, cognitive neuropsychology’s view of

humanity is frankly not worth having – an Orwellian automaton of

an information processor without a sense of self.’’

Barkley goes on to enumerate eight fundamental capacities upon

which EF, as he defines them, develop. Spatial, temporal, moti-

vational, inhibitory, conceptual/abstract, behavioral-structural, so-

cial, and cultural capacities all get their moments in the spotlight.

Although not exactly pulled out of thin air, the framework is chiefly

heuristic and derived, unapologetically, more from reason than

evidence of how the brain might actually work. However, Barkley

offers at least one intriguing, and, I think, elegantly argued, idea:

That beneath it all lie the capacities for vicarious learning and

contemplation to anticipate and manage situations that one has not

personally encountered, which are, perhaps, the game changers in

human evolution. But all this is a prelude to the next Great List that

occupies nearly half the book, a hierarchy of human functions and

activities that EF enable, and an analysis of how their effects on the

social and physical environments boomerang back to shaping the

individual’s behavioral repertoire.

These ripple effects of human activities that EF enable give rise to

the second theme, which could easily have spawned a separate book.

Barkley argues that these extended effects are the ‘‘why’’ of EF. To

explain the evolution of EF, Barkley turns to the extended phenotype

concept developed by Dawkins (Dawkins 1999). The kernel of the

extended phenotype idea is that the effects of a genotype extend

beyond the organism that houses it. When such distal effects of a

particular allele help to propagate it in succeeding generations (i.e.,

natural selection favors it), these effects are as much part of the

gene’s phenotype as, for example, hair color. Dawkins realizes that at

first glance this is an unusual way to think about gene effects, and

eases us into the idea by pointing out that the proximal effect of any

coding gene is simply to synthesize a protein. How that protein, in

tandem with other parts of the genome, gives rise to any character-

istic of the organism, is already an enormous way down the road

from that initial biochemical consequence. We could readily accept

that web construction is a rather direct consequence of a spider’s

genome. Any number of allelic variants might arise that improve the

web’s food-catching capability or that require less energy to create it,

and would be favored by natural selection. Why not regard the web

itself, or any other artifact that an organism creates, as part of the

gene’s phenotypic expression? Or, as Dawkins puts it, ‘‘In a very real

sense, her web is a temporary functional extension of her body, a

huge extension of the effective catchment area of her predatory or-

gans’’ (Dawkins 1999, p. 198). Another oft-cited example that pro-

foundly changes ecology for numerous animals is the beaver dam

that ‘‘creates a large shoreline which is safe and available for for-

aging without the beaver having to make long and difficult journeys

overland’’ (Dawkins 1999, p. 200). The genes responsible for this

behavior can claim not only the dam, but also the entire beaver lake

as part of their extended phenotype. In addition to impacts on the

environment that are favorable for propagating the responsible

genes, impacts on other organisms are part of the extended pheno-

type also. Barkley leverages this insight to argue that the capacity for

strategic interpersonal behavior is among EFs’ most decisive influ-

ences on humanity.

This thought-provoking analysis is itself worth the price of the

book, and for many readers, it will be an important introduction to

developments in evolutionary biology beyond the basics. However,

calling EFs themselves, rather than their effects, ‘‘extended phe-

notypes,’’ is not easily reconciled with Dawkins’ ideas. Barkley

skips over the ‘‘unit of evolution’’ issue that underlies Dawkins’

work: It is not the individual organism whose ‘‘fitness’’ determines

which traits are selected, but the genes themselves. The ‘‘interests’’

of the gene do not always coincide with that of the organism; it is in

that sense that the gene is selfish. Barkley implies that EFs devel-

oped because their distal effects favored the fecundity of the animal

Department of Psychiatry, Division of Child and Adolescent Psychiatry, University of Texas Health Science Center at San Antonio, San Antonio,Texas.

ISBN 978-1-4625-0535-7. 2012. New York: Guilford Press. 244 pp.

JOURNAL OF CHILD AND ADOLESCENT PSYCHOPHARMACOLOGYVolume 24, Number 6, 2014ª Mary Ann Liebert, Inc.Pp. 362–363DOI: 10.1089/cap.2014.0021

362

that performed them, and it is that animal’s self-interest that propels

the whole enterprise. The model that Dawkins prefers, of com-

plementarity of genes in a population, leads to a rather different

explanation for a number of phenomena such as empathy, coop-

erative behavior, or leadership versus followership.

Barkley’s discussion of evolutionary processes to explore ‘‘why

EF?’’ exposes him to accusations of what, for many in evolutionary

biology, is a mortal sin: Claiming that a trait arose in order to solve

a specific problem, for a purpose, or, really, for anything bearing on

‘‘why.’’ In short, that sort of teleological thinking can be a source of

fun speculation, but the hard-nosed underlying reality is that all

genetically transmitted traits, including the forerunners of human

EF, just happened to pop up as a random mishap of genetic shuf-

fling, and proliferated in the population because they happened to

improve reproductive success over the alternative alleles in that

space in the genome. Maybe this apparent purposelessness is just as

stale and ‘‘Orwellian’’ as the information-processing automaton

notions of EF that Barkley detests, but this is the playground on

which he chose to play ball.

The final chapter brings us back to more mundane concerns: The

evaluation and treatment of EF deficits. Barkley suggests that ex-

isting tests of working memory, inhibition, and planning may be

useful in assessment of some of the more basic functions at a fairly

circumscribed level (the ‘‘Instrumental – Self-Directed Level’’).

Barkley’s more expansive view of EF puts a higher premium on

human functioning in context, which brings in the higher levels of

methods and tactics. He favors direct observation and rating scale

development. The remedial and compensatory approaches men-

tioned are not path breaking – many are found in current occupa-

tional therapy textbooks (e.g., Crepeau et al. 2003) – but linking

them to the EF extended phenotype framework is an interesting

way to organize them.

The book takes the reader on a rigorous intellectual journey

through neuropsychology, evolutionary biology, and even a fair

amount of political philosophy. It would be smoother sledding if

there were more examples and hypotheticals to make the concepts

more vivid, rather than the abstract presentations that dominate.

The author might take a tip from Dawkins’ own playbook, which

shows that a technically demanding scientific exposition can be a

best-seller when the author adds lots of anecdotes about nature, and

‘‘what if’’ scenarios. All the same, this book is an important

manifesto that challenges the current zeitgeist that human func-

tioning can be reduced to simple performance tests, decontextua-

lized from the web of pressures and relationships to which we spend

a lifetime trying to adapt.

References

Crepeau EB, Cohn ES, Schell BAB: Willard and Spackman’s Occu-

pational Therapy, 10th ed. Philadelphia: Lippincott Williams &

Wilkins; 2003.

Dawkins R: The Extended Phenotype: The Long Reach of the Gene.

(Revised edition with New Afterward and Further Reading). New

York: Oxford University Press; 1999.

Address correspondence to:

Joseph C. Blader, PhD

University of Texas Health Science Center at San Antonio

Department of Psychiatry

Division of Child and Adolescent Psychiatry

7703 Floyd Curl Drive

San Antonio, TX 78229-3900

E-mail: blader@uthscsa.edu

BOOK REVIEW 363