Executive Function The Search for an Integrated Account Marie T. Banich Department of Psychology & Neuroscience, and Institute of Cognitive Science, University of Colorado at Boulder; Department of Psychiatry, University of Colorado Denver ABSTRACT—In general, executive function can be thought of as the set of abilities required to effortfully guide be- havior toward a goal, especially in nonroutine situations. Psychologists are interested in expanding the under- standing of executive function because it is thought to be a key process in intelligent behavior, it is compromised in a variety of psychiatric and neurological disorders, it varies across the life span, and it affects performance in compli- cated environments, such as the cockpits of advanced aircraft. This article provides a brief introduction to the concept of executive function and discusses how it is assessed and the conditions under which it is compromised. A short overview of the diverse theoretical viewpoints re- garding its psychological and biological underpinnings is also provided. The article concludes with a consideration of how a multilevel approach may provide a more inte- grated account of executive function than has been previ- ously available. KEYWORDS—executive function; frontal lobe; prefrontal cortex; inhibition; task switching; working memory; atten- tion; top-down control Like other psychological constructs, such as memory, executive function is multidimensional. As such, there exists a variety of models that provide varying viewpoints as to its basic component processes. Nonetheless, common across most of them is the idea that executive function is a process used to effortfully guide behavior toward a goal, especially in nonroutine situations. Various functions or abilities are thought to fall under the rubric of executive function. These include prioritizing and sequencing behavior, inhibiting familiar or stereotyped behaviors, creating and maintaining an idea of what task or information is most relevant for current purposes (often referred to as an attentional or mental set), providing resistance to information that is dis- tracting or task irrelevant, switching between task goals, uti- lizing relevant information in support of decision making, categorizing or otherwise abstracting common elements across items, and handling novel information or situations. As can be seen from this list, the functions that fall under the category of executive function are indeed wide ranging. ASSESSING EXECUTIVE FUNCTION The very nature of executive function makes it difficult to measure in the clinic or the laboratory; it involves an individual guiding his or her behavior, especially in novel, unstructured, and nonroutine situations that require some degree of judgment. In contrast, standard testing situations are structured—partic- ipants are explicitly told what the task is, given rules for per- forming the task, and provide ...

1. Executive Function
The Search for an Integrated Account
Marie T. Banich
Department of Psychology & Neuroscience, and Institute of
Cognitive Science, University of Colorado at Boulder;
Department of Psychiatry, University of Colorado Denver
ABSTRACT—In general, executive function can be thought
of as the set of abilities required to effortfully guide be-
havior toward a goal, especially in nonroutine situations.
Psychologists are interested in expanding the under-
standing of executive function because it is thought to be a
key process in intelligent behavior, it is compromised in a
variety of psychiatric and neurological disorders, it varies
across the life span, and it affects performance in compli-
cated environments, such as the cockpits of advanced
aircraft. This article provides a brief introduction to the
concept of executive function and discusses how it is
assessed and the conditions under which it is compromised.

2. A short overview of the diverse theoretical viewpoints re-
garding its psychological and biological underpinnings is
also provided. The article concludes with a consideration
of how a multilevel approach may provide a more inte-
grated account of executive function than has been previ-
ously available.
KEYWORDS—executive function; frontal lobe; prefrontal
cortex; inhibition; task switching; working memory; atten-
tion; top-down control
Like other psychological constructs, such as memory, executive
function is multidimensional. As such, there exists a variety of
models that provide varying viewpoints as to its basic
component
processes. Nonetheless, common across most of them is the idea
that executive function is a process used to effortfully guide
behavior toward a goal, especially in nonroutine situations.
Various functions or abilities are thought to fall under the
rubric
of executive function. These include prioritizing and sequencing

3. behavior, inhibiting familiar or stereotyped behaviors, creating
and maintaining an idea of what task or information is most
relevant for current purposes (often referred to as an attentional
or mental set), providing resistance to information that is dis-
tracting or task irrelevant, switching between task goals, uti-
lizing relevant information in support of decision making,
categorizing or otherwise abstracting common elements across
items, and handling novel information or situations. As can be
seen from this list, the functions that fall under the category of
executive function are indeed wide ranging.
ASSESSING EXECUTIVE FUNCTION
The very nature of executive function makes it difficult to
measure in the clinic or the laboratory; it involves an individual
guiding his or her behavior, especially in novel, unstructured,
and nonroutine situations that require some degree of judgment.
In contrast, standard testing situations are structured—partic-
ipants are explicitly told what the task is, given rules for per-
forming the task, and provided with information on task

4. constraints (e.g., time limits). Since executive function covers
a wide domain of skills, there is no single agreed-upon ‘‘gold
standard’’ test of executive function. Rather, different tasks are
typically used to assess its different facets.
One classic test often used to assess the compromise of ex-
ecutive function after brain injury is the Wisconsin Card Sorting
Test. This task is thought to measure a variety of executive
subprocesses, including the ability to infer the categories that
should guide behavior, the ability to create an attentional set
based on those abstract categories, and the ability to switch
one’s
attentional set as task demands change. Briefly, individuals
must
deduce from the experimenter’s response the rule by which the
cards should be sorted (rather than being told the rule
explicitly;
see Fig. 1a). After the initial rule is learned successfully, the
examiner changes the rule without informing the individual. At
this point the old rule must be rejected, the new rule discovered,

5. and a switch made from the old rule to the new. The ability to
exhibit such flexible readjustment of behavior is a cardinal
characteristic of executive function. Individuals with frontal
lobe damage and children younger than 4 years (who are typi-
cally tested on a two-dimensional version of the sorting task)
tend to persist in sorting items according to the previous and
now
inappropriate rule.
Address correspondence to Marie Banich, Director, Institute of
Cognitive Science, University of Colorado at Boulder, UCB
0344,
Boulder, CO 80305; e-mail: [email protected]
CURRENT DIRECTIONS IN PSYCHOLOGICAL SCIENCE
Volume 18—Number 2 89Copyright r 2009 Association for
Psychological Science
Cognitive psychologists have attempted to disentangle the
different executive subprocesses that underlie performance on
the Wisconsin Card Sorting Test, as well as to identify other
executive subprocesses. For example, the ability to switch
mental sets has been studied by presenting individuals with

6. multidimensional stimuli (e.g., a colored numeral) along with a
cue that indicates the attribute on which a response should be
based (e.g., color, or whether the number is odd or even). Indi-
viduals are slower to respond and make more errors on trials
requiring a task switch (e.g., categorize by color preceded by
categorize by odd/even) than they do on those that do not (e.g.,
categorize by color preceded by categorize by color), indicating
that task switching requires executive control (Monsell, 2003).
In other executive tasks, decisions must be based on task-
relevant information in the face of distracting information. One
such measure of this ability is the Stroop task, in which a
word’s
color must be identified while ignoring the word itself. Since
word reading is more automatic than color naming, executive
control is required to override the tendency to read or to
respond
on the basis of the word rather than the ink color. The need for
such control is reflected in slower responses when the word
names a competing ink color (e.g., the word ‘‘red’’ printed in
blue

7. ink) than when it does not (e.g., the word ‘‘sum’’ in red ink or
the
word ‘‘red’’ in red ink).
Other tasks, such as the Tower of London task, examine the
ability to plan and sequence behavior towards a goal. In this
task,
a start state and a goal state are shown, and the individual must
determine the shortest number of moves required to get the balls
from the starting state to the goal state (see Fig. 1b). An
inability
to solve the problems, taking more steps than necessary, and/or
impulsively starting to move the balls before planning are all
symptoms of executive dysfunction on this task.
THE COMPROMISE OF EXECUTIVE FUNCTION
Psychologists are interested in executive function because it is
critical for self-directed behavior, so much so that the greater
the
decrement in executive function after brain damage, the poorer
the ability to live independently (Hanks, Rapport, Millis, &
Deshpande, 1999). Normal children, adolescents, and older

8. adults also show decrements in executive function. Most notable
in children is their perseveration when required to switch tasks.
Although they can correctly answer questions about what they
should do, they nonetheless are often unable to produce the
correct motor response (Zelazo, Fyre, & Rapus, 1996).
Similarly,
parents often wonder why teenagers take risks and make im-
prudent decisions even though they seem to ‘‘know’’ better.
This
demonstrated knowledge about abstract rules coupled with an
inability to implement them, especially in the face of distracting
or conflicting information, is reminiscent of that observed in
children. The ability to plan ahead in multistep processes, to
learn about contingences between reward and punishment in
multifaceted decision-making tasks, and to exert inhibitory
control and reduce impulsive behavior continues to increase
during the teenage years and, in fact, well into the early 20s
(Steinberg, 2007). Executive function is also the cognitive
ability most affected by aging (e.g., Treitz, Heyder, & Daum,

9. 2007), with even more severe decline associated with mild
cognitive impairment and Alzheimer’s disease. Finally, execu-
tive function is compromised across a large number of psychi-
atric illnesses, including schizophrenia, bipolar disorder,
??
First Move
Second Move
FinishStart
Fourth Move
Third Move
a
b
Fig. 1. Examples of tasks often used to assess executive
function. In the
Wisconsin Card Sorting Test (a), individuals must sort cards
into one of
four piles; each card has items on it that vary along three
dimensions—
color, number, and shape—with each dimension having one of
four values
(e.g., Color: red, blue, green, or yellow; Number: 1, 2, 3, or 4;
Shape:
circle, square, triangle, or cross). Individuals must deduce the

10. correct rule
(i.e., dimension) on which to sort the cards based on feedback
provided by
the examiner about whether each choice made was correct or
incorrect.
When therule is changed,individualswith prefrontaldamage
andchildren
younger than 4 often perseverate on this type of task. They are
either
unable to learn the new rule or return to the old rule even after
they have
successfully sorted a number of trials by that new rule. In the
Tower of
London task (b), an individual is shown a series of items with
an initial state
and a goal state; on every trial, there are three pegs, which can
hold one,
two, and three balls, respectively. The individual must
determine the
shortest number of moves required to get from the initial state
to the final
goalstate.In somecases,suchas
inthesequenceshownhere,theindividual
may have to backtrack—that is, move a ball to a temporary
position (the
first move) before moving it back to its final position.
90 Volume 18—Number 2
Executive Function
depression, substance use disorders, and attention deficit
hyperactivity disorder (e.g., Willcutt, Doyle, Nigg, Faraone, &

11. Pennington, 2005).
PSYCHOLOGICAL AND NEUROBIOLOGICAL MODELS
OF EXECUTIVE FUNCTION
Even though there is agreement that damage to the frontal lobe
is
associated with compromised executive function, there is little
accord on much else—with regard either to the cognitive com-
ponents of executive function or to the manner in which the
frontal lobe supports executive function. This lack of consensus
seriously inhibits our understanding of the psychological and
neural mechanisms underlying executive function, as well as the
development of treatments to prevent or ameliorate deficits in
this area.
To somewhat oversimplify a complicated literature, one class
of models argues that executive function is an emergent
function
of a more basic, largely monolithic psychological construct like
general intelligence (g), fluid intelligence, reasoning and pro-
cessing speed, or the ability to actively maintain information

12. online to meet task demands (often conceptualized as working
memory; e.g., Salthouse & Davis, 2006). Studies examining in-
dividual differences in task performance across neurologically
intact individuals suggest that there may actually be distinct
subcomponents to executive function, including the ability to
inhibit a prepotent response, the ability to shift the task set
guiding behavior, and the ability to update the contents of
working memory. Of note, studies of twins suggest that at least
some of these subcomponents, notably response inhibition and
set shifting, appear to be separable from g (Friedman et al.,
2006).
Equally contentious are theories regarding the neural mech-
anisms of executive function. Some researchers have argued
that
lateral regions of the prefrontal cortex (PFC) are engaged across
a diverse set of demands that engage executive function
(Duncan
& Owen, 2000). Such theories are consistent with findings that
the performance of patients with frontal lobe lesions across

13. distinct tasks can be explained by a single factor. Other theories
hold, however, that distinct regions of the prefrontal cortex are
involved in different aspects of executive functions. For exam-
ple, Petrides (2005) has argued that inferior lateral regions of
the
prefrontal cortex (Brodmann Areas [BA] 45, 47) maintain in-
formation in working memory while others, notably mid-dorso-
lateral prefrontal regions (BA 9, 46), perform executive-control
operations on that information. Another theory is that control
mechanisms in the prefrontal cortex are organized in a hierar-
chical manner, with more anterior regions using internally
generated information to guide behavior and more posterior
regions using information from the environment (Christoff &
Gabrieli, 2000). Another idea, based on the pattern of
decrement
found across a battery of tests in patients with focal frontal le-
sions, is that there are three main types of executive function,
each associated with a different part of the frontal cortex. In
this

14. view, initiating and sustaining a response rely on medial frontal
regions, task setting relies on left lateral regions, and
monitoring
involved in checking and adjusting task performance over time
relies on right lateral regions (Stuss & Alexander, 2007).
Based on functional neuroimaging studies with the Stroop
task, our laboratory has taken yet another view. We suggest that
executive function involves a temporal cascade of selection
processes that are implemented at distinct way stations in the
PFC (see Fig. 2). In this model, posterior regions of the dorso-
lateral PFC (DLPFC) impose an attentional set toward task-
relevant processes. This region activates when it is difficult
to ignore information that engages a task-irrelevant process,
regardless of the type of task-irrelevant process (e.g., word
reading, color identification) or the nature of the process that
is required for the task (e.g., color identification, object identi-
fication; Banich et al., 2000). In contrast, the mid-DLPFC
selects among the specific representations identified as task-
relevant. For example, this region becomes activated for both

15. incongruent (e.g., ‘‘red’’ in blue ink) and congruent (e.g.,
‘‘red’’ in
red ink) trials in the Stroop task, because one must determine
which source of color information (that contained in the ink
color
or that contained in the word) is task-relevant (Milham, Banich,
& Barad, 2003). Posterior portions of the dorsal anterior
cingulate cortex (ACC) tend to be involved in late-stage aspects
of selection, being especially sensitive to response-related fac-
tors. This region shows the greatest activity when stimuli lead
to
two competing responses and is less sensitive to semantic types
of conflict (Milham et al., 2001). Finally, anterior regions of the
dorsal ACC appear to be involved in processes related to re-
sponse evaluation, as activity in this region increases when the
probability of making an error increases (Miham & Banich,
2005). An important part of our theory is that how much any of
these executive-control mechanisms are invoked depends on
how effectively control was applied at earlier way stations, with

16. activity in the ACC being affected by how well regions of
DLPFC
impose control. For example, with increased practice at a Stroop
task, activity in the DLPFC drops slightly, but that of the pos-
terior dorsal ACC diminishes greatly as control by DLPFC
becomes more effective (Milham, Banich, Claus, & Cohen,
2003). Conversely, relative to younger adults, older adults show
less DLPFC activity but increased cingulate activity (Miham
et al., 2002), which is consistent with the cascade-of-control
model.
TOWARD AN INTEGRATED MODEL
How can all these different conceptions of executive function be
reconciled? This is a major challenge facing the field today. In
pursuit of a more integrated account of executive function, our
laboratory is working collaboratively along with others at the
University of Colorado and the University of Illinois under the
auspices of a National Institute of Mental Health center grant to
Volume 18—Number 2 91
Marie T. Banich

17. link theories of executive function across different levels of
analysis. We are considering the nature of executive function at
three distinct levels: the neurobiological (at the level of both
neurotransmitters and brain systems), the psychological, and
the computational. Our goal is to consider how information at
each of these levels can be linked, and thereby lead to a theory
of
executive function that can better account for the many
disparate
pieces of knowledge currently available.
One example of an issue being actively examined within our
center is the nature of executive processes involved in the im-
position and switching of task sets. Our computational models,
as well as empirical studies ofneurotransmitter function, suggest
that dopaminergic connections from the basal ganglia to the
frontal cortex act as a gate, signaling whether one should
hold onto the information currently being maintained in
working memory or clear it out to allow new information to

18. enter
(O’Reilly, 2006). These findings raise the possibility that
genetic
variation in dopaminergic function influences the maintenance
and switching of task sets, a possibility we are currently inves-
tigating. At the level of brain systems, one major area affected
by
this gating would be the posterior portion of the DLPFC, which
according to our cascade-of-control model is involved in creat-
ing and maintaining an attentional set. Moreover, recent work
by
colleagues at the University of Illinois suggests that these same
posterior regions of the DLPFC are involved in creating and
maintaining an ‘‘affective’’ set, as activity in this region during
attentionally demanding tasks differs between depressed and
nondepressed individuals (Herrington et al., 2009). Develop-
mental research in our center shows, at the psychological and
computational levels, that a child’s ability to create abstract
representations of categories predicts her or his task-switching
abilities (Kharitonova, Chien, Colunga, & Munakata, in press).

19. One potential explanation is that actively maintained task-set
representations are relatively weak in children. They only be-
come stronger, as well as more abstract and able to be general-
ized, with practice or experience. Hence, a new task set with
3
Posterior dorsal ACC:
Select the information that
should guide responding
4
Anterior dorsal ACC:
Evaluate the response
W
C
mid-DLPFC:
Bias to task-relevant representations
21
WB
CG
RB
RG
Posterior DLPFC:

20. Bias to task-relevant processes
Fig. 2. Thecascade-of-
controlmodelofexecutivefunctioninfrontalcortex.Here we
showhow the
cascade-of-control model (Banich et al., 2000; Milham &
Banich, 2005; Milham, Banich, Claus, &
Cohen, 2003; Milham et al., 2002) would explain performance
on the Stroop task. The example
shown is for the word ‘‘blue’’ printed in green ink. The
direction of the cascade is indicated by the
dashed arrows. First, posterior regions of the dorsolateral
prefrontal cortex (DLPFC; 1) create
and impose a top-down attentional set for task-relevant goals. In
this case, a top-down attentional
set is imposed toward activation of brain regions involved in
ink-color identification (C). This bias
must be strong (as denoted by the thick line) to counteract the
automatic bias (noted by a thin line)
toward brain regionsthat areinvolvedin wordprocessing (W).
However, thistop-down attentional
set cannot overcome a lifetime of word reading, so selection
must occur among the representations
that are identified as related to color. We argue that mid-DLPFC
(2) selects which of the repre-
sentations,mostlikelybeing activelymaintained, is mosttask
relevant. Herethe selectionwouldbe
toward the ink color green (CG) as compared to the word
‘‘blue’’ (WB). Next, posterior regions of
the dorsal anterior cingulate cortex (3) must determine what
information should be used in de-
termining the response (R), in this case selecting the response
(either verbal or manual) associated
with green (RG) as compared to the response associated with
blue (RB). However, if selection by
prior regions in the cascade (i.e., those in DLPFC) is poor, the

21. posterior dorsal cingulate must also
deal with any unresolved issues of selection from prior way
stations in the cascade before a re-
sponse can be emitted. Finally, more anterior regions of the
dorsal anterior cingulate cortex (ACC;
4) are involved in response evaluation. If such an evaluation
suggests that an incorrect response
was made, these anterior regions of the dorsal ACC send a
signal back to posterior-DLPFC, telling
it to assert top-down control more strongly.
92 Volume 18—Number 2
Executive Function
which a child lacks experience will be relatively weak compared
to a prior task set that has been used repeatedly on preceding
trials.
These are some of our first steps at linking neurobiological,
psychological, and computational approaches in an effort to
better understand executive function. How might such an inte-
grated account be helpful? We believe that a more integrated
account may aid in the design of new interventions for
executive
dysfunction. For example, our findings suggest the possibility

22. that training people in building abstract categories may bolster
aspects of executive function such as task switching. One diffi-
culty with training regimens is that sometimes their results are
not immediately apparent but are only seen down the road.
Brain
imaging might provide a means to determine whether additional
or different regions come on line during the course of training
even before behavioral changes are manifest. Studies with drug
interventions might provide another way to bolster engagement
of brain regions necessary for executive function. In sum, an
integrated understanding of executive function should open up
new avenues for intervention to aid individuals who have com-
promised executive functioning because of a psychiatric disor-
der, brain damage, aging, or other factors.
Recommended Reading
Jurado, M.B., & Rosselli, M. (2007). The elusive nature of
executive
function: A review of our current understanding.
Neuropsychology
Review, 17, 213–233. A longer review of executive function
from
the perspective of neuropsychology, linking behavior to brain

23. systems.
Miyake, A., Friedman, N.P., Emerson, M.J., Witzki, A.H.,
Howerter, A.,
& Wager, T.D. (2000). The unity and diversity of executive
func-
tions and their contributions to complex ‘‘frontal lobe’’ tasks:
A
latent variable analysis. Cognitive Psychology, 41, 49–100.
Out-
lines the argument for separable subcomponents of executive
function, drawn from a cognitive and individual-differences
perspective.
Royall, D.R., Lauterbach, E.C., Cummings, J.L., Reeve, A.,
Rummans,
T.A., Kaufer, D.I., et al. (2002). Executive control function: A
re-
view of its promise and challenges for clinical research. A
report
from the Committeeon Research of the
AmericanNeuropsychiatric
Association. Journal of Neuropsychiatry & Clinical
Neurosciences,
14, 377–405. Discusses the psychiatric and medical disorders
that

24. are associated with compromised executive function, how
execu-
tive function is assessed in clinical settings, and the linkage of
executive function with functional outcome; also discusses chal-
lenges in designing treatments for executive dysfunction.
Acknowledgments—The author would like to thank Gregory
Burgess, Wendy Heller, Gregory A. Miller, Yuko Munakata, and
Randy O’Reilly for comments on earlier versions of this manu-
script. The author would also like to thank all the members of
the Interdisciplinary Behavioral Science Center on the
Determinants of Executive Function and Dysfunction (NIMH
P50 MH079485) for their contributions to some of the ideas
presented in this article. Finally the author would like to
acknowledge the support of NIMH Grants P50 MH079485
and R01 MH070037, on which she serves as Principle Investi-
gator, and NIMH Grant R01 MH061358 (Wendy Heller,
Principal Investigator).
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Week 2 Review Part 2: Essay Question
[WLOs: 1, 2, 5, 6] [CLOs: 1, 2, 3, 4]
The writing assignment this week is the second part of the
Weekly Review activity. You have received your randomized
essay question as the final part of your Week 2 Review Part 1:
Objective Questions activity. You will copy and paste this
prompt into a word document and write a short essay that
addresses the prompt. The prompts will be associated with real-
life scenarios; however you will use your Study Guide to
prepare. This portion of your Weekly Review cannot be retaken
as you were able to retake the Part 1 Objective Questions. The
essay question will be graded by the instructor and not
automatically. Feedback will be given so you can improve your
performance throughout the course.
Your essay
· Must be two to three double-spaced pages in length (not
including the reference page) and formatted according to APA
style as outlined in the Ashford Writing Center (Links to an
external site.)’s APA Style (Links to an external site.)
· No title page is required.

42. · Must utilize academic voice. See the Academic Voice (Links
to an external site.) resource for additional guidance.
· Must begin with an introductory paragraph that has a distinct
thesis statement.
· A thesis statement is required because it is important to tell
your reader what you are going to inform them about. It should
clearly state the topic and the stance you are taking about this
topic. This can also help you to make sure you stay on topic
within your paper.
· Not sure how to write a clear thesis? Try using the Ashford
University Writing Center’s Thesis Generator (Links to an
external site.) or Writing a Thesis Statement (Links to an
external site.)
· Must end with a conclusion that summarizes your thought.
· Tell your reader why or how you have proven your position on
the topic.
· For assistance on writing Introductions & Conclusions (Links
to an external site.), refer to the Ashford Writing Center.
· Must address the topic of the essay with critical thought.
· Must use at least one scholarly source in addition to your
required course text, citing also within the body of writing as
support for your stance.
· The Scholarly, Peer-Reviewed, and Other Credible
Sources (Links to an external site.) table offers additional
guidance on appropriate source types. If you have questions
about whether a specific source is appropriate for this
assignment, please contact your instructor. Your instructor has
the final say about the appropriateness of a specific source for a
particular assignment.
· Must document, in APA style, any information used from
sources with citations and as a list of references, at the end of
the essay. See the Formatting Your References List (Links to an
external site.) resource in the Ashford Writing Center for
specifications.