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 underwhich 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; workingmemory; 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 provided with information on task
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 theWisconsin 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, individualsmust
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,
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: marie.banich@colorado.edu.
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
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
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
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,
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). Individualsmust deduce the 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 the rule is changed, individualswith prefrontal damage 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 showna series of itemswith 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 goal state. In some cases, suchas in the sequence shownhere, the individual may have to backtrack—that is, move a ball to a temporary position (the first move) before moving it back to its final position.
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