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NEUROCASE
2010, iFirst, 1–22
Cognitive and neural components of the
phenomenology of agency
NNCS
BASIC COMPONENTS OF AGENCY
Ezequiel Morsella,1,2 Christopher C. Berger,1 and Stephen C. Krieger3
1
Department of Psychology, San Francisco State University, San Francisco, CA, USA
Department of Neurology, University of California, San Francisco, CA, USA
3
Department of Neurology, Mount Sinai Medical Center, New York, USA
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2
A primary aspect of the self is the sense of agency – the sense that one is causing an action. In the spirit of recent
reductionistic approaches to other complex, multifaceted phenomena (e.g., working memory; cf. Johnson &
Johnson, 2009), we attempt to unravel the sense of agency by investigating its most basic components, without
invoking high-level conceptual or ‘central executive’ processes. After considering the high-level components of
agency, we examine the cognitive and neural underpinnings of its low-level components, which include basic consciousness and subjective urges (e.g., the urge to breathe when holding one’s breath). Regarding urges, a quantitative
review revealed that certain inter-representational dynamics (conflicts between action plans, as when holding one’s
breath) reliably engender fundamental aspects both of the phenomenology of agency and of ‘something countering
the will of the self’. The neural correlates of such dynamics, for both primordial urges (e.g., air hunger) and urges
elicited in laboratory interference tasks, are entertained. In addition, we discuss the implications of this unique
perspective for the study of disorders involving agency.
Keywords: Sense of agency; Phenomenology of agency; Self consciousness; Volition; Conscious conflict; Cognitive
control.
INTRODUCTION
What we call a body is only a bundle of sensations; and what we call the mind is only a bundle
of thoughts, passions, and emotions, without any
subject.
—Thomas Reid’s (1785/1855, p. 119) criticism of
Hume’s conclusion that the self is nothing more
than a bundle of sensations.
When attempting to unravel the scientific basis of
phenomena as perplexing and multifaceted as the
‘sense of self’ or the ‘sense of ownership’ (Synofzik,
Vosgerau, & Newen, 2008a), it has been fruitful to
consider how the phenomena may arise from basic
component cognitive and neural processes. Such a
reductionistic approach has been instrumental in
the study of working memory, another multifaceted phenomenon (cf. Johnson & Johnson, 2009).
In this spirit, we focus on the basic cognitive and
neural nuts-and-bolts of a primary aspect of the
sense of self: the sense of agency, that is, the sense
that one is causing a physical or mental act (Engbert,
Wohlschläger, & Haggard, 2008; Sato, 2009;
Synofzik, Vosgerau, & Newen, 2008b). The main
burden of this review is to demonstrate that, just as
fundamental aspects of working memory have
been unveiled by focusing on basic component
processes (e.g., the ‘top-down’ re-activation of
Address correspondence to Ezequiel Morsella, Ph.D., Assistant Professor, Social Cognitive Neuroscience, Department of
Psychology, San Francisco State University (SFSU), 1600 Holloway Avenue, EP 301, San Francisco, CA 94132-4168, USA.
(E-mail: [email protected]).
© 2010 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business
http://www.psypress.com/neurocase
DOI: 10.1080/13554794.2010.504727
2
MORSELLA ET AL.
representations through the act of refreshing; Johnson & Johnson, 2009), much can be unraveled
about the sense of agency (‘agency’, for short) by
examining low-level component processes. We
focus on the nature of the interactions among
action-related representations and explain how the
resulting subjective urges (‘urges’, for short) form
an essential part of the ‘bundle of sensations’ constituting the sense of agency.
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Outline of article
The aim of this treatise is to begin to understand
the cognitive, neural, and physiological underpinnings of the most basic components of agency. To
do so, we first review briefly the high-level components of agency. Second, we justify our approach,
in which agency can arise without a ‘supervisory
system’ (Angell, 1907; Norman & Shallice, 1980),
‘central executive’ (Baddeley, 1986), or other,
homuncular-like agent in the brain. In this section,
we argue that, regardless of whether Hume (1739/
1888, Part IV, Sect. 6) is right or wrong, with the
knowledge at hand it is progressive to attempt to
explain agency as if he were right. It is then that we
discuss the non-conceptual, low-level components
of agency, including basic consciousness,1 the skeletal
muscle output system, and subjective urges.
Regarding urges, we present the results of a quantitative review of inter-representational dynamics
(e.g., conflict between action plans, as when holding
one’s breath) giving rise to urges and to ‘something
countering the will of the self’. Last, we discuss the
implications of our conclusions for the study of
disorders involving agency.
HIGH-LEVEL COMPONENTS: CONCEPTUAL
AND ATTRIBUTIONAL PROCESSES
High-level component processes of agency are based
on the perception of the lawful correspondence
1Throughout this
article, we refer only to the most basic form
of consciousness, often referred to as ‘subjective experience’,
‘qualia’, ‘sentience’, ‘basic awareness’, and ‘phenomenal state’.
Perhaps this basic form of consciousness has been best defined
by Nagel (1974), who claimed that an organism has phenomenal states if there is something it is like to be that organism –
something it is like, for example, to be human and experience
pain, love, breathlessness, or yellow afterimages. Similarly,
Block (1995) claimed, ‘the phenomenally conscious aspect of a
state is what it is like to be in that state’ (p. 227).
between action intentions and action outcomes
(Haggard & Clark, 2003; Hommel, 2009; Wegner,
2003). If one has the intention of flexing one’s finger
and then the finger happens to flex, for example,
one is then likely to sense that one caused the
action. This attribution is the outcome of a high
level, conceptual process (Jeannerod, 2009; Synofzik
et al., 2008b) that takes into account information
from various contextual factors (Moore, Wegner,
& Haggard, 2009; Wegner & Wheatley, 1999),
including motor efference (Cole, 2007; Engbert
et al., 2008; Sato, 2009; Tsakiris, Schütz-Bosbach,
& Gallagher, 2007), proprioception (Balslev, Cole,
& Miall, 2007; Knoblich & Repp, 2009), and the
perception of the real-world consequences of one’s
intentions (Synofzik, Vosgerau, & Lindner, 2009).
It has been proposed that this conceptual process,
resulting in ‘the “I” of “I did that”’ (Engbert et al.,
2008, p. 693), is used to explain other forms of causation (Epley, Waytz, & Cacioppo, 2007; Wegner
& Wheatley, 1999).2 Matching intentions to outcomes also influences agency in the mental realm
(Bortolotti & Broome, 2009): If one intends on
imagining a Mondrian and then experiences the
relevant imagery, then one may believe that one
caused the imagery, even when the percept may
have been caused by an experimental trick, as in
the Perky effect3 (Perky, 1910). Thus, by manipulating contextual factors, scores of experiments
have demonstrated that subjects can be fooled into
believing that they caused actions that were in fact
caused by something else (Wegner, 2002). For
example, when a participant’s hand controls a
computer-drawing device behind a screen such that
the participant cannot see his or her hand in
motion, the participant can be fooled into thinking
(through false feedback on the computer display)
that the hand intentionally moved in one direction
when it actually moved in a slightly different direction (Fourneret & Jeannerod, 1998). With such
techniques, participants in another study were
tricked into believing that they could control the
2One detects agency in oneself, for example, when one’s
intentions satisfy the Humean causal principles of consistency,
priority, and exclusivity: Our intentions should be consistent
with, and be experienced at an appropriate interval prior to, the
relevant action, and there should be no other cause for the
action (Wegner & Wheatley, 1999). For a treatment of the temporal properties of agency, see Sarrazin, Cleeremans, and Haggard (2008).
3
In the Perky effect, experimental subjects are fooled into
believing that they are imagining an image that is actually presented physically on a screen.
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BASIC COMPONENTS OF AGENCY
movements of stimuli on a computer screen
through a phony brain-computer interface (Lynn,
Berger, Riddle, & Morsella, in press).
The opposite effect – the sense that ‘I did not
intend that’ – has also been induced experimentally.
When intentions and outcomes mismatch, people
are less likely to perceive actions as originating
from the self (Wegner, 2002). It seems that agency
is diminished more by discrepant information
regarding the nature of an action (e.g., direction of
an arm movement) than by discrepant information
regarding its timing (Farrer, Bouchereau, Jeannerod,
& Franck, 2008a). In a functional MRI experiment,
when intentions of subjects mismatched action
outcomes, subjects reported decreased agency. In
addition, activity in the temporo-parietal junction,
a region that is important for ideomotor learning
(Hommel, 2009), increased as a function of the
degree of action-intention mismatch (Spengler,
von Cramon, & Brass, 2009; see related findings in
Farrer et al., 2008b). Similarly, mismatches involving one’s intended speech and what one actually
hears oneself say are associated with decreased
gamma-band coherence (an index of functional
synchrony) between frontal and temporal lobes
(Ford, Gray, Faustman, Heinks, & Mathalon,
2005).
Most of these studies examine how agency is
influenced by intention-outcome mismatches or
illusory intention-outcome matches. Because these
high-level components of agency arise from judgments from a high-level conceptual system (Jeannerod, 2009; Synofzik et al., 2008b), it is likely that
many of their subcomponents are shared by other
rational processes, such as those used for inferring
physical cause-and-effect relationships. There are
several ‘comparator models’ explaining how intention-outcome mismatches are detected and influence various levels of agency. Different theorists
link the sense of agency and urges to different
phases of the process (cf. Berti & Pia, 2006; David,
Newen, & Vogeley, 2008; Haggard, 2005, 2008).
Figure 1 illustrates the primary components of
such models.
LOW-LEVEL COMPONENTS: URGES AND
BASIC CONSCIOUSNESS
Basic component processes of agency are associated with the actual intending itself – the subjective
feeling of intending that accompanies the control
of ongoing physical and mental action (Pacherie,
3
Figure 1. Primary components of a comparator model of
agency, in which a ‘comparator’ detects intention-outcome mismatches on the basis of discrepant afference from the world/
body, or from reafference (e.g., corollary discharge). Different
theorists link the sense of agency and urges to different phases
of the process. Based on Berti and Pia (2006) and Haggard
(2005).
2008). Such a feeling is closer to the phenomenology
of agency than to the concept of agency discussed
above. This phenomenology of agency requires the
components of an inclination (or urge) and basic
consciousness. The components are experienced
together in dramatic form when one holds one’s
breath or refrains from dropping a hot dish. Presumably, such subjective states can occur independent of the aforementioned conceptual
processes that are necessary to ascribe actions to
the self, as in ‘I did it’ or ‘It is I who am observing
this’ (Crick & Koch, 2000; James, 1890; Jeannerod,
2009; Merker, 2007; Synofzik et al., 2008b). It has
been proposed that these basic urges exist in nonhuman mammals (Denton, McKingley, Farrell, &
Egan, 2009; Gray, 2004; Merker, 2007). Insofar as
something akin to the urge to breathe can arise
without high-level conceptual processes (Denton
et al., 2009), then one must explain the nature of
such non-conceptual processes when reducing
agency into its component parts. This is the aim of
this section.
Assumptions of the approach
Before examining these basic components, we must
justify our reductionistic approach in which agency
is explained without invoking the actions of a
‘supervisory system’ (Angell, 1907; Norman &
Shallice, 1980), ‘central executive’ (Baddeley,
1986), or other, homuncular-like agent in the brain
whose presiding over action is a necessary ingredient
of agency. Although it is tempting to say that an
action is ‘voluntary’ only when ‘one’ intends to do it,
there are strong a priori considerations (the fallacy of
ad infinitum) and empirically-based considerations
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4
MORSELLA ET AL.
(e.g., Libet, 2004) that render such a position
unscientific (Morsella & Bargh, in press). (For supporting evidence, see Curtis & D’Esposito, 2009;
Kimberg, D’Esposito, & Farah, 1997; Roepstorff
& Frith, 2004.) This conclusion is evident in article
titles with phrases such as What’s at the Top in the
Top-Down Control of Action? (Roepstorff & Frith,
2004), In Search of the Wild Homunculus (Logan,
2003), and Banishing the Homunculus (Hazy,
Frank, & O’Reilly, 2006). In this vein, James
(1890) proposed that, not only is it theoretically
unnecessary to propose that conscious thought
must be the object of some ‘observer’, but that,
when introspecting, one is unable to find any evidence of there being such an observer: James
reported that, through his mind’s eye, he encountered nothing but sensations, inclinations, and
other ideas, that is, only the objects of the observer
with no observer to be found. Supporting this
view, recent neural evidence demonstrates that,
when introspecting about two different kinds of
perceptual events, there is no common brain region
activated during both acts of introspection
(Guggisberg, Dalal, & Nagarajan, 2009), as if
there were no ever-present observer.
Regardless of whether Hume was right or
wrong, we propose that, at this stage of understanding of the nervous system, it is progressive
to ‘theory build’ as if Hume were correct – that
is, to explain as much as possible regarding
agency by appealing to low-level processes. It
is important to note that ideomotor theory
(cf. Hommel, 2009), the prevalent theory
addressing the nature of voluntary action, satisfies this criterion.
In ideomotor theory, the mere thoughts of
actions produce impulses that, if not curbed or
controlled by ‘acts of express fiat’ (i.e., exercise of
veto), result in the performance of those imagined
actions (James, 1890). James added that this was
how voluntary actions are generated: The image
of the sensorial effects of an action leads to the
corresponding action – effortlessly and without
any knowledge of the motor programs involved
(why motor programs are unconscious is
addressed by Gray, 1995, 2004; Grossberg, 1999;
Rosenbaum, 2002). Importantly, in ideomotor
accounts there is no single homunculus in charge
of suppressing one course of action in order to
express another course of action, consistent with
the empirically-based conclusion that ‘no single
area of the brain is specialized for inhibiting all
unwanted actions’ (Curtis & D’Esposito, 2009,
p. 72). With respect to the mechanisms of suppression, ideomotor theory refers not to a homunculus
reining action in but rather to the influence of an
incompatible idea (i.e., a competing action plan).
From this standpoint, action plan A may in the
morning oppose plan B, and in the evening plan C
may conflict with D, with there never being the
same third party (a homunculus) observing both
conflicts.
By studying such dynamics among representations, much can be learned about the component
processes of agency, without invoking a central
executive. Interactions among plans can lead to
urges, a primary low-level component of agency.
We now focus on inter-representational dynamics
and assess which dynamics are intimately-related
to agency. Emulating recent reductionistic
approaches to working memory (Johnson & Johnson,
2009), in our approach we first identify a component process and only then attempt to isolate its
neural correlates.
Inter-representational dynamics
As is evident in our examples of conflict, subjective
perturbations tend to arise from representations
competing for the control of action. According to
Supramodular Interaction Theory (SIT; Morsella,
2005), representations competing for action selection must lead to strong perturbations because the
primary function of consciousness is to integrate
incompatible skeletomotor intentions. Thus, conscious conflicts (Morsella, 2005) are automatically
triggered by incompatible skeletomotor plans, such
as when one holds one’s breath while underwater,
suppresses emotions, or inhibits a prepotent
response in laboratory interference paradigms. No
such conflicts emerge from intersensory conflicts,
perceptual conflicts, or from non-skeletal muscle
effectors (e.g., smooth muscle conflict in the pupillary reflex; Morsella, Gray, Krieger, & Bargh,
2009a). Regarding the conflicts occurring at the
different stages of processing, consciousness is
required to integrate information at the responseselection stage.
From this standpoint, in the nervous system
there are three distinct kinds of integration or
‘binding’ (Morsella & Bargh, in press). Perceptual
binding (or afference binding) is the binding of perceptual processes and representations (Figure 2A,
top). This occurs in intersensory binding, as in the
McGurk effect,4 and in intrasensory, feature binding
BASIC COMPONENTS OF AGENCY
S
S
S
R
S
R
S
R
(A)
(B)
Integrated
Action
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Associated to Self / Will
S
R
(C)
S
R
Integrated
Action
Against Self / Will
Figure 2. Three forms of binding in the brain, with only efference–efference binding requiring basic consciousness. S (sensory) signifies ‘perceptual/afference’, and R (response) signifies
‘motor response’. (A) Afference binding and efference binding.
(B) Efference–efference binding. (C) In efference–efference
binding, the self is associated with one of the conflicting plans;
the other plan is perceived as something countering the will of
the self.
(e.g., the binding of shape to color; Zeki & Bartels,
1999). Another form of binding, linking perceptual
processing to action/motor processing, is known as
efference binding (Haggard, Aschersleben, Gehrke,
& Prinz, 2002) (Figure 2A, bottom). This kind of
stimulus-response binding is what allows one to
learn to press a button when presented with a cue
in a laboratory paradigm. Research has shown that
responding on the basis of efference binding can
occur unconsciously. For example, Taylor and
McCloskey (1990, 1996) demonstrated that, in a
choice response time (RT) task, subjects could
select the correct motor response (one of two
button presses) when confronted with subliminal
stimuli (see review in Hallett, 2007).
4
The McGurk effect (McGurk & MacDonald, 1976) involves
interactions between visual and auditory processes: An observer
views a speaker mouthing ‘ba’ while presented with the sound
‘ga’. Surprisingly, the observer is unaware of any intersensory
interaction, perceiving only ‘da’.
5
The third kind of binding, efference–efference
binding, occurs when two streams of efference
binding are trying to influence skeletomotor
action at the same time (Figure 2B). This occurs
when one holds one’s breath or suppresses a prepotent response. In SIT, it is the instantiation of
conflicting efference–efference binding that
requires consciousness. Consciousness is the
‘crosstalk’ medium that allows such actional
processes to influence action collectively. Absent
consciousness, behavior can be influenced by
only one of the efference streams, leading to unintegrated actions such as unconsciously inhaling
while underwater or reflexively removing one’s
hand from a hot object (Morsella & Bargh, in
press). According to SIT, one can breathe unconsciously, but consciousness is required to suppress breathing. Similarly, one can unconsciously
emit a pain-withdrawal response, but one cannot
over-ride such a response without consciousness.
Response systems are inflexible in that, without
consciousness, they are incapable of taking
information generated by other systems into
account. For example, the tissue-damage system
is ‘encapsulated’ in the sense that it will protest
damage (e.g., from running across the desert
sand to reach water) even when the action engendering the damage is lifesaving (Morsella, 2005).
Thus, regarding agency, inclinations can
be behaviorally suppressed, but not mentally
suppressed (Bargh & Morsella, 2008). Representations of inclinations function like ‘internalized
reflexes’ (Vygotsky, 1962), which is consistent
with Sherrington’s (1941) definition of pain as,
‘the psychical adjunct of an imperative protective
reflex’ (p. 286).
NEURAL BASIS OF THE BASIC
COMPONENTS OF AGENCY
If, as if according to Hume and ideomotor theory, there is no self observing this or that mental process, nor favoring one versus another
action plan during conflict, then what is left
apart from the activation of action plans? Plans
alone are insufficient to instantiate agency:
these representations must be conscious, for
unconscious representations and processes
alone are incapable of engendering ‘voluntary’
(or, ‘integrated’) actions (Morsella & Bargh, in
press). We now review two basic components of
agency.
6
MORSELLA ET AL.
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Basic consciousness and the skeletal muscle
output system
It is often taken for granted that, in a diagram of
the divisions of the nervous system, including the
autonomic system (with its parasympathetic and
sympathetic components influencing smooth muscle, cardiac muscle and glands) and somatic system
(influencing skeletal muscle), the self and agency
are intimately associated only with the latter. SIT
explains why skeletal muscle is voluntary muscle
without invoking an agentic ‘doer’: Skeletomotor
actions are at times ‘consciously mediated’ because
they are directed by multiple, encapsulated systems
that, when in conflict, require consciousness to
yield adaptive action. Figuratively speaking, multiple systems in the brain are trying to control the
same ‘steering wheel’ (i.e., the skeletal muscle system) – expressing (or suppressing) inhaling, blinking, pain withdrawal, and micturating all involve,
specifically, skeletal muscle actions/plans. Accordingly, regarding processes such as digestion, one is
conscious of only those phases requiring coordination with skeletomotor plans (e.g., chewing) and
none of those that do not (e.g., peristalsis). Conversely, no skeletal muscle plans are directly
involved in unconscious processes such as the
pupillary reflex, peristalsis, bronchial dilation, and
vasoconstriction (all involving smooth muscle).
Just as a prism combines different colors to yield a
single hue, consciousness integrates simultaneously
activated tendencies to yield adaptive skeletomotor
action, as captured by the acronym PRISM: parallel responses into skeletal muscle (Morsella, 2005).
Neural correlates of basic consciousness
and the cortical-subcortical controversy
Not requiring conscious crosstalk, unconscious
processes involve smaller networks of brain areas
than their conscious counterparts (Gaillard et al.,
2009; Sergent & Dehaene, 2004), and automatic
behaviors (e.g., reflexive pharyngeal swallowing)
involve substantially fewer brain regions than their
intentional counterparts (e.g., volitional swallowing; Kern, Jaradeh, Arndorfer, & Shaker, 2001;
Ortinski & Meador, 2004). Such a network
approach has led to the hypothesis that consciousness requires a form of thalamocortical interaction
(or resonance) between thalamic ‘relay’ neurons
and cortical neurons (Coenen 1998; Edelman &
Tononi 2000; Edelman, Baars, & Seth 2005; Llinás,
Ribrary, Contreras, & Pedroarena, 1998; Ojemann
1986), but this is inconsistent with the fact that we
consciously experience aspects of olfaction even
though the afferents from the olfactory sensory
system bypass the thalamus and directly target
regions of the ipsilateral cortex (Morsella, Krieger,
& Bargh, 2010a; Shepherd & Greer, 1998). This is
not to imply that conscious olfaction does not
require the thalamus: in later, post-cortical stages
of processing, the thalamus does receive inputs
from cortical regions that are involved in olfactory
processing (Haberly, 1998).5 Buck (2000) proposes
that conscious aspects of odor discrimination
depend primarily on the activities of the frontal
and orbitofrontal cortices; Barr and Kierman
(1993) propose that olfactory consciousness
depends on the pyriform cortex. These proposals
appear inconsistent with subcortical accounts of
consciousness (Merker 2007; Penfield & Jasper
1954).6 As explained below, the tension between
cortical versus subcortical accounts (the ‘corticalsubcortical controversy’, for short) of consciousness is a recurring theme in the study of agency.
Regarding neuroanatomy, consciousness has
been linked to the ‘ventral processing stream’ of
the brain, which is not necessary for action execution but for knowledge-based action selection
(Goodale & Milner, 2004, p. 48). (Substantial
research, including that of the dorsal visual processing stream [Goodale & Milner, 2004], reveals
that online motor control can occur unconsciously;
Rosenbaum, 2002.) Thus, the consensus is that
only a subset of the central nervous system is
necessary for sustaining basic consciousness (see
review in Morsella et al., 2010a). For instance,
5As well, this does not imply that the pre-cortical, relay thalamus is unnecessary for other forms of consciousness (e.g., visual, auditory, or haptic) or that, within the olfactory system, no
structure carries out a function similar to that of the thalamus
(see Kay & Sherman, 2007). A critical empirical question is
whether the olfactory system can generate some form of consciousness (a ‘microconsciousness’; Zeki & Bartels, 1999) by
itself or whether olfactory consciousness requires interactions
with other, traditionally non-olfactory regions (Cooney &
Gazzaniga, 2003). For instance, perhaps one becomes conscious
of olfactory percepts only when they crosstalk with other systems or influence processes that are motor (Mainland & Sobel,
2006) or semantic-linguistic (Herz, 2003).
6
Investigations on the neural correlates of phantosmias
(Leopold, 2002) and conscious versus unconscious olfactory
processing may resolve this controversy. Regarding the former,
it has proven difficult to identify the minimal region(s) whose
stimulation is sufficient to induce olfactory hallucinations
(Mizobuchi et al., 1999).
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BASIC COMPONENTS OF AGENCY
although the absence of the spinal cord or cerebellum leads to sensory, motor, cognitive, and affective deficits, it does not seem to eradicate such a
form of consciousness (Schmahmann, 1998). Similarly, although extirpation of the amygdalae or
hippocampi leads to anomalies including severe
deficits in affective processing (LeDoux, 1996) and
episodic memory (Milner, 1966), respectively, it
seems that such an identifiable form of consciousness persists without these structures. Regarding
the cerebral cortex, extensive investigations on
‘split-brain’ patients (Wolford, Miller, & Gazzaniga, 2004), binocular rivalry7 (Logothetis & Schall,
1989), and split-brain patients experiencing binocular rivalry (O’Shea & Corballis, 2005) strongly
suggest that basic consciousness does not require
the non-dominant (usually right) cerebral cortex
nor the commissures linking the two cortices.
Investigations regarding prefrontal lobe syndromes (Gray, 2004) and the psychophysiology of
dream consciousness, which involves prefrontal
deactivations (Muzur, Pace-Schott, & Hobson,
2002), suggest that, although the prefrontal lobes
are involved in cognitive control (see review in
Miller, 2007), they are not essential for the generation of basic consciousness. According to Gray
(2004), one is conscious, not of high-level executive
processes or motor efference, but only of perceptual-like contents. (Importantly, Fodor [1983]
reached the same conclusion on different grounds.)
Consistent with these views, Koch and Tsuchiya
(2007) provide substantial evidence that cognitive
control and attentional processing are distinct
from basic consciousness.
Establishing the cortical-subcortical controversy, Penfield and Jasper (1954) concluded from
observations of awake patients undergoing brain
surgeries involving ablations and direct brain stimulation that, although the cortex may elaborate the
contents of consciousness, it is not the seat of consciousness. To them, consciousness is primarily a
function of subcortical structures. Recently, based
7
In binocular rivalry (Logothetis & Schall, 1989), an observer
is presented with different visual stimuli to each eye (e.g., an
image of a house in one eye and of a face in the other). It might
seem reasonable that, faced with such stimuli, one would perceive an image combining both objects – a house overlapping a
face. Surprisingly, however, an observer experiences seeing only
one object at a time (a house and then a face), even though both
images are always present. At any moment, the observer is
unaware of the computational processes leading to this outcome; the conflict and its resolution are unconscious.
7
on such evidence and clinical observations of anencephaly, Merker (2007) re-introduces this hypothesis
in a theoretical framework in which consciousness is
primarily a phenomenon associated with mesencephalic areas (e.g., zona incerta). It seems reasonable to conclude that consciousness can persist
even when great quantities of the cortex are absent
(Merker, 2007). The question remaining is whether
an identifiable form of consciousness (e.g., primordial urges) can exist despite the non-participation
of all cortical matter.
Neural correlates of efference–efference
binding in primordial urges
Of all the bundles of sensations that are experienced
phenomenologically, perhaps efference–efference
binding during conflict is the basic process that is
most associated with agency. Previous research has
focused on how agency is influenced by intentionoutcome mismatches, but little research has examined how agency is influenced by conflict, a basic
conscious state. The idea of a self battling an
action plan is captured by the ‘monkey on one’s
back’ metaphor that is often used to describe the
conflicting tendencies associated with aspects of
addiction. Most exemplary, in Freud’s (1938)
framework of the id, ego, and superego, primitive
animalistic urges (e.g., libidinal urges from the id)
stem from something that is perceived to be distinct from the self (i.e., the ego). Accordingly, when
performing trials in response interference paradigms (see below), participants perceive the activation of plans as less associated with the self when
the plans conflict with intended action than when
the same plans lead to no such interference (Riddle
& Morsella, 2009; Riddle, Rosen, & Morsella,
2010). Efference–efference binding is thus a basic
process associated with a basic aspect of agency –
the sense of something countering the will of the self
(Riddle & Morsella, 2009) (Figure 2C).
There is now substantial research on the neural
correlates of primordial urges (see review in Denton
et al., 2009). As reviewed in Denton et al. (2009)
and Liotti et al. (2001), the feeling of the urge to
breathe while holding one’s breath is associated
with a distributed network including the insula and
limbic/paralimbic areas of the brain, a network
that overlaps with those found for other primal
emotions, such as thirst (Denton et al., 2009; Egan
et al., 2003), hunger for food, micturition, and pain
(Liotti et al., 2001). More specifically, ‘air hunger’
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8
MORSELLA ET AL.
is associated with activations in the anterior insula
(Banzett et al., 2000), anterior cingulate cortex
(ACC), operculum, cerebellum (Parsons et al.,
2001), amygdala, thalamus, and basal ganglia
(Evans et al., 2002); frontoparietal attentional networks also participate in this state (Evans et al.,
2002). Evans et al. (2002) conclude that the insula is
essential for dyspnea perception, but that it works
in concert with a larger neural network. Air hunger
is accompanied by deactivations in the dorsal cingulate, posterior cingulate, and prefrontal cortex
(Brannan et al., 2001). In another study (Egan
et al., 2003), thirst was associated with activations
in the ACC, parahippocampal gyrus, inferior and
middle frontal gyri, insula, and cerebellum. As
thirst is quelled, activity in ACC decreases. The
ACC is also associated with cravings for cocaine
(Wexler et al., 2001) and alcohol (Myrick et al.,
2004, see review in Franken, Zijlstra, Booij, & van
den Brink, 2006). The insula and ACC are also
involved in the urge to blink (Lerner et al., 2008).
Re-awakening the cortical-subcortical controversy
of Penfield and Jasper (1954), Grossman (1980) proposes that, regarding urges, the urge cannot arise
without cortical participation: ‘Although the anterior thalamic and possibly mesencephalic and pontine brainstem are necessary for consciousness, they
are probably not sufficient – interaction of the rather
small masses of neurones with at least a certain volume of limbic cortex or neocortex must occur’ (cited
in Liotti, 2001, p. 2039). Thus, it has been difficult to
isolate the most minimal number of brain regions
that could give rise to a basic consciousness involving an urge (Morsella et al., 2010a).
Another challenge in isolating the subjective
effects and neural circuits involved in these primordial scenarios is that consciousness is inherently
multidimensional and can be influenced both by
the nature of ongoing cognitive processing and by
the resultant consequences of such processing
(Gray, 2004). Thus, it is difficult to distinguish the
‘processing-based’ subjective effects (primary
effects) of conflicts from their indirect subjective
effects (secondary effects; Morsella et al., 2009a).
When holding one’s breath, for example, one presumably experiences both the effects of sustaining
efference–efference binding as well as secondary
effects, such as the subjective effects caused by the
afference arising from the bodily consequences of
breathlessness (as noted in Evans et al., 2002).
Hence, it is easier to draw conclusions from
laboratory tasks, which are less ‘visceral’ and
introduce little if any secondary effects. Moreover,
these tasks include control conditions that allow
one to distinguish the effects of the critical process
(e.g., efference–efference binding) from more general effects, such as those associated with affect,
motor control, and cognitive control.
Laboratory tasks inducing efference–
efference binding
There are several laboratory tasks that reliably
induce efference–efference binding with minimal
secondary effects, but only recently have investigators begun to examine the subjective aspects of
these tasks (Morsella et al., 2009b). Hence, there
are very little data regarding the subjective aspects
of conflicts. We now review the selection of tasks
that have yielded some data.
In all reported studies, urges were measured
after each trial. In general, participants were asked
a question (e.g., ‘How strong was your urge to
make a mistake?’ or ‘How strong was the thought
of a competing response?’), and then responded
using a Likert scale, in which 1 signified the bottom-end of the continuum (e.g., ‘no urge to err at
all’) and the highest number signified the other end
(e.g., ‘extremely strong urge’). In most studies, an
8-point scale was used.
In the classic Stroop task (Stroop, 1935), participants are instructed to name the color in which a
word is written. When the word and color are
incongruous (e.g., RED presented in blue),
response conflict leads to increased error rates,
RTs, and reported urges to make a mistake
(Morsella et al., 2009a). When the color matches
the word (e.g., RED presented in red), or is presented on a neutral stimulus (e.g., a series of x’s as
in ‘XXXX’), there is little or no interference (see
review in MacLeod & MacDonald, 2000). It has
been proposed that, in the incongruent condition,
there is conflict between word-reading and colornaming plans (Cohen, Dunbar, & McClelland,
1990). This condition can be construed as eliciting
efference–efference binding; the neutral condition
can be construed as a case of regular efference
binding8 (Figure 2B).
One limitation of this task is that it compares the
dynamics between two action plans that differ in
8
The nature of the interaction between the color-naming and
word-reading plans in the incongruent condition has been the
object of much current research and theorizing (for distinct
views, see Eidels, Townsend, & Algom, 2010, and Roelofs, 2010).
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BASIC COMPONENTS OF AGENCY
9
Figure 3. Schematic of sample stimuli from congruent (left column) and conflict-related conditions (rightmost column), with the latter
including efference–efference binding. (A) MacLeod and Dunbar shape and color naming task. (B) Stroop task. (C) Flanker task. (D)
Multi-source interference task.9 (E) Antisaccade task, with congruent (e.g., looking toward the bright stimulus) and incongruent (e.g.,
looking away from the bright stimulus) conditions. (F) Sustained intentions task. In the middle are sample stimuli from conditions
involving regular efference binding with minimal perceptual interference. For A, the neutral condition involves naming the shape when
presented without color. No such intermediate conditions exist for tasks D through F.
various ways from each other (e.g., color-naming is
not automatic and taxes the semantic systems,
whereas word reading is automatic and can
by-pass the semantic system; Cohen et al., 1990).
MacLeod and Dunbar (1988) developed a Strooplike task without this shortcoming. In it, participants are trained to name nonsense shapes using
color names. For instance, the participant is
instructed to name a six-sided polygon as ‘orange’.
Following training, participants are instructed to
name the colors in which the shapes happen to be
presented. On congruent trials, the shape and color
are congruent (e.g., the shape ‘orange’ is presented
in orange). On incongruent trials (involving
efference–efference binding), the shape and color
name are different. For example, the same six-sided
polygon will appear in blue and the participant
must respond ‘blue’, leading to interference
(MacLeod & MacDonald, 2000) (Figure 3A). In a
second phase, participants are instructed to name
the shapes and disregard the colors in which the
shapes are presented. In the incongruent condition,
newly acquired shape-naming plans interfere with
color-naming plans (MacLeod & MacDonald,
2000). Thus, one can measure within a single
session the interference effects of each stimulus-
related plan, because the plan that is task-irrelevant in one phase (e.g., shape naming) of the
session is task-relevant in the other, and vice versa.
The paradigm is also ‘purer’ than the Stroop in
that intended and interfering plans involve the
same kind of action (naming).
A limitation of this task and the Stroop task is
that the incongruent conditions cannot be used to
distinguish the effects of interference occurring at
different stages of processing (e.g., at perceptualsemantic levels or response selection levels).9 The
Eriksen flanker task (e.g., Eriksen & Schultz, 1979)
has been used to show that introducing interference
at different stages of processing leads to distinct
behavioral, neural, and subjective effects (Coles,
9
A reliable interference task that induces even more kinds of
interference than these two tasks is the multi-source interference
task (MSIT; Bush, Shin, Holmes, Rosen, & Vogt, 2003). In one
version of this task, subjects are instructed to indicate the oddball stimulus in an array of three stimuli (e.g., 113) by pressing
one of three buttons. Interference arises, for example, when participants must press the third button to indicate that the first
stimulus is the oddball, as when presented with 311 (Figure 3D).
This task includes elements of spatial and flanker interference
(Stins, van Leeuwen, & de Geus, 2005).
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10
MORSELLA ET AL.
Gratton, Bashore, Eriksen, & Donchin, 1985;
Morsella et al., 2009b; van Veen, Cohen, Botvinick, Stenger, & Carter, 2001). In one version of the
task, participants are trained to press one button
with one finger when presented with the letter S or
M and to press another button with another finger
when presented with the letter P or H. Participants
are then instructed to respond to the stimulus presented in the center of an array (e.g., SSPSS,
SSMSS, targets underscored) and to disregard the
flanking distracters (Figure 3C). RTs and selfreported ‘urges to err’ are greater when distracters
are associated with a response that is different
from that of the target (response interference [RI];
e.g., SSPSS) than when the distracters are different
in appearance but associated with the same
response (perceptual interference [PI]; e.g.,
SSMSS; Morsella et al., 2009b), a difference attributed to the automatic activation of response codes
by distracters (Eriksen & Schultz, 1979; Coles
et al., 1985; Morsella & Miozzo, 2002; see review in
Levine, Morsella, & Bargh, 2007). Responses are
fastest when flankers and targets are identical (e.g.,
SSSSS). In this task, efference–efference binding is
induced in the RI condition. In our quantitative
review (see below), we include two versions of the
flanker task that tax working memory. In one version (Morsella, Rigby, Hubbard, & Gazzaley,
2010b; Table 1, Sample 7), participants are
instructed to hold two stimuli (e.g., the ‘S’ and ‘P’
of the flanker task) in mind until a cue prompts
them to respond to one of the two stimuli; in
another version (Morsella et al., 2010b; Table 1,
Sample 6), participants are instructed to respond
to the letter in the center of the screen (the target)
but to delay responding until they see a subsequent
letter (the distracter), with participants instructed
to disregard the characteristics of distracters and
emit only the response associated with the target.
Another task involving the suppression of prepotent action plans is the antisaccade task (Curtis &
D’Esposito, 2009; Hallett, 1978). In the incongruent condition, participants are instructed to look
away from a briefly presented salient stimulus (e.g.,
a bright light or loud sound). Performance is faster
and less effortful in the congruent, ‘pro-saccade’
condition, in which participants are instructed to
look at the stimulus (Figure 3E). (For the neural
correlates of the self-control during the execution of
eye movements, see Curtis & D’Esposito, 2009;
Husain, Parton, Hodgson, Mort, & Rees, 2003.)
One limitation of these paradigms is that the
incongruent conditions involve more than just the
activation of incompatible action plans, the proposed critical ingredient of conscious conflict
(Morsella, 2005). These conditions also involve a
host of executive processes and the suppression of
(often pre-potent) action plans (e.g., Stroop and
flanker tasks; Cohen et al., 1990; DeSoto, Fabiani,
Geary, & Gratton, 2001; MacLeod & MacDonald,
2000). Similarly, in real world cases of efference–
efference binding (e.g., holding one’s breath or
refraining from dropping a hot dish), incompatible
action plans are often inextricably co-mingled with
secondary effects such as need deprivation and
noxious stimulation, as mentioned above.
The sustained intentions task (Morsella et al.,
2009a) was designed to diminish the influence of
these confounds. In this task, while in a motionless
state, participants introspect subjective aspects of
their experience while holding in mind incompatible
intentions (e.g., to point left and right with the same
finger), congruent intentions (e.g., two commands to
point left with the same finger), and compatible (coexpressible) intentions (e.g., pointing left with a given
finger and vibrating that finger) (Figure 3F). By activating incompatible plans without behavioral performance, the incompatible condition distills the
subjective effects of efference–efference binding.10
There is evidence that, for all these tasks, trial-bytrial subjective effects are not due to participants
observing their own RTs. For example, the subjective effects are still robust in a flanker-like interference paradigm (Morsella et al., 2009b; Table 1,
Sample 4), in which participants are instructed to
withhold responding for over a second, which
eradicates RT effects (Eriksen & Schultz, 1979).
Moreover, in the sustained intentions task, the
effects are present when participants sustain
incompatible intentions (e.g., to point left and
right) in a motionless state in which no response is
emitted (Morsella et al., 2009a). In addition,
though post-error corrections in interference paradigms involve improved performance (e.g., faster
RTs) on trials following a trial involving response
interference (e.g., an incongruent trial), reported
urges to err actually increase in such a trial, which
10
In the variations of this task reported in our quantitative
review, participants are first trained to introspect their urge to
make a mistake while performing the Stroop task, and then they
are told that what they introspected was something called
‘activity’ (i.e., activity from interference/conflict) and that they
must now introspect ‘activity’ during the sustained intentions
task. Without such training, it is difficult for participants to
identify the subjective dimension of interest.
11
Antisaccade
Flanker (letter stimuli)
Flanker (shape stimuli)
Flanker (delayed response)
Flanker (letter stimuli)
Flanker (working memory, one item in mind)
Flanker (working memory, two items in mind)
MacLeod and Dunbar color and shape-naming
Multi-source interference task∼
Stroop (vocal)
Stroop (subvocal)
Stroop (vocal) †
Stroop (subvocal) †
Stroop (vocal) †
Stroop (subvocal) †
Stroop (vocal) ∞
Stroop (vocal, subliminal [masked] stimuli)
Stroop (vocal) §
Stroop (vocal) §
Stroop (vocal)
Stroop (vocal) *
Stroop (vocal) °
Sustained intentions (finger movements)∼
Sustained intentions (arm movements) *
Sustained intentions (finger movements) °
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Urge to err
Activity from interference/conflict
Activity from interference/conflict
Activity from interference/conflict
Activity from interference/conflict
Urge to err
Urge to err
Perceptions of competition
Activity from interference/conflict
Perceived difficulty
Urge to err
Perceptions of competition
Perceptions of competition
Urge to err
Urge to err
Perceptions of competition
Urge to err
Urge to err
Perceived exerted control
Urge to err
Urge to err
Urge to err
Activity from interference/conflict
Activity from interference/conflict
Activity from interference/conflict
Measure of ‘Something Countering
the Will of the Self’
1.28
1.29
1.00
0.86
0.89
0.30
0.86
0.65
1.64
0.82
1.57
1.52
1.32
1.58
1.33
0.68
0.29
1.04
0.40
1.09
2.03
2.15
2.48
1.63
2.55
1.18***
674
ddiff1
26
28
21
16
9
32
18
84
20
19
15
33
33
34
34
35
33
19
19
64
22
14
14
18
14
N
90***
1.56
1.69
1.43
1.46
1.17
0.60
0.30
1.04
0.37
1.08
0.94
0.74
0.33
0.97
0.17
0.76
0.54
ddiff2
Morsella, Zarolia, and Gazzaley (in press)
Morsella et al. (2009b)
Morsella et al. (2009b)
Morsella et al. (2009b)
Morsella, E. (unpublished data)
Morsella et al. (2010b)
Morsella et al. (2010b)
Riddle et al. (2010)
Kang et al. (2008; and unpublished data)
Etkin, A. (unpublished observations)
Morsella et al. (2009b)
Morsella et al. (2009b)
Morsella et al. (2009b)
Morsella et al. (2009b)
Morsella et al. (2009b)
Riddle et al. (2010)
Rigby et al. (2010)
Lynn, Riddle, and Morsella (2010)
Lynn et al. (2010)
Rigby and Morsella (2009)
Morsella et al. (2009a)
Morsella et al. (2009a)
Kang et al. (2008)
Morsella et al. (2009a)
Morsella et al. (2009a)
Source
Because there are so little data on the subjective aspects of conflict and interference, for this analysis, we included as much data as possible regarding the Stroop task, including data from
the ‘introspection training’ sessions of the sustained intentions task. Thus, some data from the different tasks come from the same subject. This is denoted by the matching symbols. Because
cognitive process, and not study, was the unit of analysis, this does not affect the conclusions drawn about the effects of the cognitive process.
a
Meta-analytic average.
Taska
Sample
TABLE 1
Perception of ‘something countering the will of the self’ as a function of task and experimental condition: Effect sizes for congruent versus conflict (efference–efference binding),
ddiff1, and efference binding (with some perceptual interference) versus conflict (efference–efference binding), ddiff2
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12
MORSELLA ET AL.
has been explained as a dissociation between
implicit measures of performance (e.g., RT) and
explicit measures (e.g., self-reports about task difficulty; A. Etkin, personal communication, July 1,
2009). Similarly, though learning a new action plan
toward a stimulus decreases the strength of previously-acquired urges toward that stimulus, RT is
not influenced to the same degree (Berger &
Morsella, 2010). These data are consistent with the
finding that RT does not always correlate with
subjective measures (Morsella et al., 2009b).11
There is also evidence that such ratings are not
based on folk beliefs regarding how someone
should behave in a psychological experiment
(Morsella et al., 2009b). For example, the ratings
are not fixed but change systematically as a function of trial number, and effects are found with
Stroop stimuli that are subliminal (Rigby, Poehlman,
& Morsella, 2010; Table 1, Sample 17).
Quantitative review of the subjective effects
of efference–efference binding from a
selection of representative interference tasks
In our quantitative review, we analyzed how urges
and self-vs-not self ascriptions vary as a function of
interference condition. The aim of the analysis is
not to review all the pertinent conflict-related data
(though we estimate that few, if any, data points
have been overlooked), but to home in on the common, basic component process that engenders
urges in a representative sample of various laboratory tasks. Hence, the unit of analysis was the kind
of cognitive process rather than the study. For one
analysis, we pooled subjective data falling under
the classification, ‘perception of something countering the will of the self’, comprising data regarding
perceptions of competition, perception of a competing response, urge to err, perceptions of difficulty,
and perceptions of exerted effort (see Table 1). In
our second analysis, we pooled subjective data
regarding the opposite dimension, ‘perceptions of
self-control’, comprising data regarding perceptions
of personal control.
11
It may be that urges and RTs are both distinct consequences of conflict, but that it is difficult, if not impossible, to
separate the two. Observing one’s RTs could influence judgments regarding urges; given the difficulty of introspecting RTs
at this time scale (Buzsáki, 2006; Libet, 2004), perhaps urges too
could inform judgments about RTs.
Aggregate d effect sizes and tests of the effect
sizes were estimated with Comprehensive MetaAnalysis 2.0 using a fixed effects approach. The
fixed effects method provides a more precise and
reliable estimate of the effect size than might be
obtained with a random effects approach (Cooper,
1998). The analysis reveals that, building on demonstrations that action plans conflicting with
intended action are perceived as foreign to the self
(Riddle et al., 2010), in each and every task it was
efference–efference binding that reliably produced
the strongest subjective perturbations associated
with ‘something countering the will of the self’ (see
Table 1 for each d effect size and sample size).
When comparing the conflict (efference–efference)
group to the no conflict (congruent) group, the
mean weighted d effect size (ddiff1) across samples
using fixed effects analysis was 1.18 (95% CI = 1.08 −
1.27; Z = 24.58). When comparing the conflict
(efference–efference) group to the group having
regular efference binding with minimal perceptual
interference, the mean weighted d effect size (ddiff2)
across samples using fixed effects analysis was .90
(95% CI = .79 − 1.01; Z = 16.03). As revealed in
congruent conditions and in conditions associated
with normal efference-binding, the absence of such
binding is often associated with increased ‘perceptions of self-control’ (Table 2). When comparing
the conflict (efference–efference) group to the no
conflict (congruent) group, the mean weighted d
effect size (ddiff1) across samples using fixed effects
analysis was –.54 (95% CI = −.36 − −.73; Z = 5.69).
When comparing the conflict group to the regular
efference binding group, the mean weighted d
effect size (ddiff2) across samples using fixed effects
analysis was –.57 (95% CI = −.38 − −.76; Z = 5.90).
These effects from efference–efference binding
are reliably found even when (a) effectors are not
called into play, as with mental action (e.g., subvocalization; Samples 11, 13, 15, 27), (b) participants
are in a motion-less state (the sustained intentions
task), (c) task difficulty and observations of RT are
taken into account, (d) some of the stimuli are held
in working memory (Samples 6 and 7), and (c) with
responses to subliminal stimuli (Sample 17). The
subvocalization data corroborate the notion that
similar effects are obtained for externalized and
internalized actions (Bargh & Morsella, 2008;
Vygotsky, 1962) and that these subjective effects
do not stem only from conflict at the level of effector activation.
Consistent with our finding, effort at the
response selection stage is construed as being
BASIC COMPONENTS OF AGENCY
13
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TABLE 2
Perceptions of self-control as a function of task and experimental condition: Effect sizes for congruent versus conflict
(efference–efference binding), ddiff1, and efference binding (with some perceptual interference) versus conflict
(efference–efference binding), ddiff2
Sample
Task measuring perceptions of self-control
26.
27.
28.
29.
MacLeod and Dunbar color and shape-naming !
Stroop (subvocal) †
Stroop (vocal) †
Stroop (vocal) ∞
N
ddiff1
ddiff2
Source
84
34
34
35
−0.34
−0.74
−0.81
−0.54
−0.33
−0.79
−0.93
−0.56
Meta-analytic average
187
–.54***
–.57***
intimately associated with conscious processing
and with the ‘conflict type of stress’ (Sanders,
1983, p. 81). (For a case in which Stroop performance is dissociated from subjective effort, see Naccache et al., 2005; for contradictory evidence, see
Modirrousta & Fellows, 2009.) More generally, the
results are consistent with the observation that, figuratively speaking, people tend not to experience
any mental strife while experiencing intersensory
conflicts such as ventriloquism or the McGurk
effect (McGurk & MacDonald, 1976), but such is
apparently not the case while they perform the
Stroop task or exert self-control (Baumeister &
Vohs, 2004). It is important to appreciate that, in
principle, a hypothetical nervous system could
function differently, with conflicts among perceptual
processes being the conflicts that are most taxing.
The data reveal that agency may also have an
interesting relationship with what occurs during
the opposite of conflict, that is, during harmonious
processing. That urges to err are low for the congruent Stroop condition is interesting because it is
known that participants often read the stimulus
word inadvertently in the congruent condition of
the Stroop task: ‘The experimenter (perhaps the
participant as well) cannot discriminate which
dimension gave rise to the response on a given
congruent trial’ (MacLeod & MacDonald, 2000,
p. 386). (For thorough treatments of this controversial issue, see Eidels, Townsend, & Algom,
2010, and Roelofs, 2010.) Urges to err for the congruent condition are comparable to those of the
‘neutral’ condition of the Stroop task, in which the
color is presented on an illegible letter string
(Morsella et al., 2009b). In addition, in a withinsubjects Stroop manipulation, ‘urges to read’ are
greater when words are presented in standard
black font than when the same words are presented
in a congruent color (Molapour, Berger, &
Morsella, 2010), suggesting that the act of color-
naming masks introspection of the reading process
which may be occur automatically (Morsella et al.,
2009b). This finding has been explained as an
instance of double-blindness, in which one is unaware that two distinct cognitive operations are activated when the operations lead to the same action
plan (Morsella et al., 2009b). The notion is consistent with the view that one is conscious only of the
‘outputs’ of processes, not of the processes themselves (Lashley, 1951). Regarding agency, this signifies that, when there is conflict, the organism makes
self-vs-other ascriptions, and that, when there is
congruence (or harmony), the organism might not
even know that two processes transpired.
Riddle et al. (2010)
Morsella et al. (2009b)
Morsella et al. (2009b)
Riddle et al. (2010)
Neural correlates of efference–efference
binding in two representative tasks
The ACC has been shown to be most active when
contrasting Stroop incongruent and neutral conditions (MacLeod & McDonald, 2000). This brain
region, mentioned in the review of primordial
urges above, is located on the medial surface of the
frontal lobe and is interconnected with many
motor areas. Exactly what the ACC does in interference tasks remains controversial, as there are
various proposals regarding its function (cf.
Botvinick, 2007; Brown & Braver, 2005; Cohen
et al., 1990; Enger & Hirsch, 2005; Mayr, 2004).
(Regarding the intimate relationship between ACC
activation and the autonomic system, see Critchley
et al., 2003.)12 Activation in the ACC is often
followed by ramped up activation in control
12
It has been concluded that, in the Stroop task, inadvertent
reading may be occurring in congruent trials. This may explain
the strange observation that, compared to the neutral condition, the congruent condition, too, yields increased activation of
the ACC (cf. MacLeod & McDonald, 2000).
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14
MORSELLA ET AL.
regions of the brain, such as the dorsolateral prefrontal cortex, which then leads to improved performance (Cohen et al., 1990). During Stroop
performance, this may occur by having top-down
processes increase the activation of task-relevant
dimensions (e.g., attending to color) and decrease
the activation of task-irrelevant dimensions (e.g.,
attending to the word; Gazzaley, Cooney, Rissman, & D’Esposito, 2005; Enger & Hirsch, 2005).
Because most of these studies have focused on the
Stroop task, it has been challenging to distinguish
the neural correlates of perceptual interference
from response interference, for the reasons mentioned above.
In a neuroimaging study addressing this issue
(van Veen et al., 2001), it was found that, though
both response and perceptual interference are associated with differences in performance, only the
former activates the ACC. Building on this literature, in an analysis of the activations accompanying two dissimilar interference tasks (the MSIT, see
footnote 9, and sustained intentions task), it was
revealed that dorsal ACC was engaged by the
increased subjective conflict associated with
response conflict, but only when a motor response
was required (Kang, Morsella, Shamosh, Bargh, &
Gray, 2008). Activations that were uniquely associated with subjective conflict were found in the preand post-central sulcus: Left somatosensory and
possibly motor areas were uniquely engaged by
subjective conflict, regardless of the demand for
motor activity. These regions are known to be
responsible for furnishing the contents of working
memory (Buchsbaum & D’Esposito, 2008), which
is intimately related to consciousness and action
selection (Baddeley, 2007). Consistent with this
finding, regarding the contents of working memory, it has been proposed that one should be conscious only of perceptual-like representations (e.g.,
phonological representations in the phonological
loop; Baddeley, 2007) and not of the motor-like
processes (e.g., the articulatory code in the phonological loop), whether the motor-like process be for
action control or executive control (Gray, 1995,
2004; Morsella, Molapour, & Lynn, in press). A
perceptual-like representation constitutes that
which is consciously experienced in several different contexts – normal action, dreams, and when
observing the actions of others (Rizzolatti, Sinigaglia, & Anderson, 2008). For example, it is the
phonological representation (and not, say, the
motor-related articulatory code) that one is
conscious of during both spoken and subvocalized
speech, or when perceiving the speech of others
(Fodor, 1983; Rizzolatti et al., 2008). There is an
obvious distinction phenomenologically between
perceptual and motor representations (with the latter being unconscious; Gray, 2004; Grossberg,
1999; Rosenbaum, 2002), but it has been challenging to tease apart the neural substrates of the
motor-end versus perceptual-end mechanisms of
verbal working memory (Buchsbaum &
D’Esposito, 2008; Leff et al., 2009).
GENERAL DISCUSSION
In attempting to explain agency without invoking a
‘self’ or high-level conceptual processes, we are left
with (a) basic consciousness and (b) representations competing for the control of action. Our
approach is unique in that we focus on low-level
processes associated with conflict rather than on
high-level mechanisms associated with mismatches
between intentions and outcomes, processes which
rely on conceptual processing (Jeannerod, 2009;
Synofzik et al., 2008b). As predicted by theory
(Morsella, 2005), efference–efference binding reliably elicits strong subjective perturbations, supporting the prediction that, unlike regular efference
binding (which can occur unconsciously; Hallett,
2007), this form of binding requires basic consciousness, an essential component of agency. Such
binding is also accompanied by the sense of something countering the will of the self. The effect is
contextual: In one context, action plan A may be
linked to agency; in another context, the plan may
be perceived as countering the self, as in the case of
suppressed visceral urges (i.e., the ‘monkey on
one’s back’; Riddle & Morsella, 2009) (Figure 2C).
In a study that attempted to isolate the neural
correlates of efference–efference binding in two
dissimilar interference tasks having minimal secondary effects (Kang et al., 2008), activations
uniquely associated with efference–efference binding and subjective conflict were associated with
brain regions known to be involved in working
memory, a phenomenon intimately associated with
conscious action selection (Baddeley, 2007).
Our review suggests that, for a complete theory
of agency, the minimal neuroanatomy capable of
constituting a basic conscious state (e.g., that involving an urge) must be identified. Unfortunately, the
neural findings we reviewed raised more questions
than did the behavioral data. Regarding the substrates engendering basic consciousness and urges,
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BASIC COMPONENTS OF AGENCY
the controversy continues about the primacy of
cortical versus subcortical structures. Apart from
this controversy, and despite the consensus that
basic consciousness is associated with only a subset
of all regions and processes (Crick & Koch 2003;
Gray 2004; Grossberg, 1999; Koch, 2004; Logothetis & Schall 1989; Merker 2007; Weiskrantz
1992; Zeki & Bartels 1999), some researchers propose that consciousness can be constituted at a
small scale (e.g., by a unique set of cells in particular brain regions; Koch 2004) while others propose
that it requires large-scale synchronization of
‘equipotential’ elements across the brain (Greenfield, 2000). Regardless of whether consciousness is
primarily a cortical or subcortical phenomenon,
there does seem to be the consensus that it is constituted by processes in the ventral thalamocortical
stream (Goodale & Milner, 2004). (This is consistent with accounts regarding the neurological condition of sensory neglect; Heilman, Watson, &
Valenstein, 2003.) Regarding urges, one observation that seems to counter this overarching framework is that weak electrical stimulation of the presupplementary motor area, a region of the dorsal
stream, leads to the experience of the urge to move
a body part, with stronger stimulation leading to
movement of the same body part (Fried et al.,
1991; cited in Haggard, 2008). However, it may be
that such activation leads to feedback (e.g., corollary discharge) that is then ‘perceived’ by perceptual areas associated with the ventral system (Lau,
Rogers, & Passingham, 2007), which would be
consistent with research proposing that only perceptual products are conscious (Gray, 2004). As
mentioned above, teasing apart the neural correlates of a motor-like mechanism from its perceptual-like feedback is more than challenging
(Buchsbaum & D’Esposito, 2008). Research on the
neural correlates of subvocalizing may illuminate
the issue (cf. Heuttig & Hartsuiker, 2009; Leff
et al., 2009).
In SIT, the conscious state permits the ‘votes’
from different systems to be taken into account
for adaptive action selection. Accordingly, in disorders in which action seems to be decoupled
from basic consciousness, behavior is often perceived as impulsive, situationally inappropriate,
and uncooperative (Chan & Ross, 1997; Rankin,
2007). For example, in alien hand syndrome
(Bryon & Jedynak, 1972), anarchic hand syndrome
(Marchetti & Della Sala, 1998), and utilization
behavior syndrome (Lhermitte, 1983), brain damage causes hands and arms to function autono-
15
mously, carrying out relatively complex goaldirected behavior (e.g., the manipulation of
objects; Yamadori, 1997) that are maladaptive
and, in some cases, at odds with a patient’s
reported intentions. Regarding agency, patients
may describe such actions as dissociated from
their conscious will (Marchetti & Della Sala,
1998). Although such phenomena have been
explained as resulting from impaired supervisory
processes (e.g., Shallice, Burgess, Shon, & Boxter,
1989), SIT proposes that they are symptoms of a
more basic condition – the lack of adequate crosstalk among actional systems. Similarly, in some
forms of frontotemporal lobar degeneration
(FTLD), among many symptoms, there is abnormal action selection during flanker-like tasks
(Krueger et al., 2009; Luks et al., 2010) and poor
decision-making in both risk-taking contexts (see
review in Roca et al., 2010) and social contexts
(Rankin, 2007). In such disorders, it seems that
basic consciousness is retained but that action
selection is maladaptive (e.g., impulsive, rigid, or
socially inappropriate), as if the ‘votes’ (or inclinations) from certain systems are no longer being
cast. (This is consistent with the ‘somatic marker’
hypothesis; Damasio, 1994.) We propose that
subjective measures such as urges may reveal
which representations are absent (or participating
weakly) during pathological decision-making
processes. For example, in some contexts, urges
may reveal more about aspects of processing than
behavioral or psychophysiological measures.
Consider that, in one flanker task, the size of the
subjective effect was larger than that of the
behavioral RT effect (Morsella et al. (2009b,
Study 4A). We believe that, just as RT can reveal
aspects of cognitive processing that may not be
detectable through less subtle behavioral measures (e.g., response accuracy), measures of subjective aspects of processing may illuminate
features of cognitive processing that are undetectable in standard behavioral and psychophysiological measures.
Consistent with a crosstalk view of consciousness, perhaps consciousness is not instantiated by
the mere activation of a network of specific neuroanatomical loci, but rather by there being a certain
mode of interaction among loci. It seems that,
regarding the outcome and nature (e.g., whether
conscious or unconscious) of processing, the mode
of interaction among regions is as important as the
nature and loci of the regions (Buzsáki, 2006;
Gazzaley, Rissman, & D’Esposito, 2004; Gazzaley
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16
MORSELLA ET AL.
et al., 2005). For example, the presence or lack of
interregional synchrony leads to different cognitive
and behavioral outcomes (Hummel & Gerloff,
2005; see review of neuronal communication
through ‘coherence’ in Fries, 2005). For example,
during binocular rivalry (see Footnote 7), it is only
while experiencing a percept consciously that perceptual processing associated with the percept is
coupled with motor-related processes in frontal cortex (Doesburg, Green, McDonald, & Ward, 2009).
It may be that such a motor-like, top-down signal
is necessary for consciousness of any urge. This is
consistent with the conclusion that every form of
consciousness is a relatively slow brain process
(Gray, 2004; Lau, 2009; Libet, 2004), requiring ‘reentrant’ processing sustained by top-down signals
(Llinás et al., 1998; Llinás & Ribary, 2001; Tong,
2003). From this standpoint, research on the neural correlates of subliminal versus conscious visual
perception reveals that the first ‘feedforward’
stream of activation from posterior to frontal areas
is unconscious, though it can influence behavior,
cognition, and emotion (Morsella & Bargh, in
press). Consistent with this view, during binocular
rivalry (see Footnote 7), voluntary action can
influence which percept enters consciousness
(Maruya, Yang, & Blake, 2007).13
Regarding agency, although top-down signals
may be necessary for consciousness, this does not
imply that there is a single top-down signal whose
business it is to serve as the sole, ever-present
‘introspectioner’: As mentioned above, when introspecting about two different kinds of perceptual
events, there is no common brain region activated
during both acts of introspection (Guggisberg
et al., 2009). At first glance, it seems that the need
for sustained activation (e.g., through top-down
control) for the instantiation of any kind conscious
percept is at odds with the observation that hallucinations and earworms (e.g., a tune that one ‘cannot get out of one’s head’) occur involuntarily.
However, research suggests that there is a topdown component in such phenomena, but that,
because of aberrant corollary discharge mechanisms, the activation is not attributed to the self
(Mathalon & Ford, 2008). Accordingly, evidence
supports the hypothesis that the speech production
13
The object that moves in synchrony with participants’ voluntary movements is conscious for longer periods of time and
unconscious for shorter periods of time. Similar effects can be
obtained, not only with top-down motor signals, but with topdown attentional shifts (Paffen, Alais, & Verstraten, 2009).
system is involved in the generation of auditory
hallucinations (Ford et al., 2005; Green &
Kinsbourne, 1990).
Apart from outstanding questions regarding
the basic neural components of agency, certain
theoretical issues remain opaque. It is clear that
consciousness is more a talker than a doer,
because so much can be achieved unconsciously
with respect to both action and cognition. Yet,
though there are theories that address why consciousness accompanies some processes but not
others (Morsella, 2005), and even why its contents
seem as they do (i.e., being ‘perceptual-like’:
Fodor, 1983; Morsella, Molapour, & Lynn, in
press; Gray, 1995), no theory has begun to
address why the contents require ‘phenomenality’
in order to be crosstalked or broadcasted. What is
it about the physical underpinnings of consciousness that permits such a form of communication?
The answer to this question may require more
than just empirical developments; it may require a
dramatic reconceptualization of what is already
known about the physical basis of cognition
(Grossberg, 1987).
Emulating recent approaches that reduce a
complex phenomenon to basic mechanisms
before identifying its neural underpinnings
(Johnson & Johnson, 2009), we sought to unravel
the sense of agency without invoking a ‘self’ or
high-level conceptual processes. Each of the tenets of our approach is highly falsifiable. For
example, because aspects of an attentional network have been identified in the neural correlates
of both visceral urges and urges from interference
tasks, it could be that an urge is conscious only
when it enters a form of processing such as working memory (LeDoux, 1996) or high-level conceptual processing (Rosenthal, 1991), which
would be at odds with the assumptions of our
approach. Such a falsification would nevertheless
advance our understanding of agency. Regarding
conceptual processing, though a continuous conflicting urge seems very different phenomenologically from an intention-outcome mismatch,
perhaps the conflicting urge is nothing more but
the reiterative cycling of the kind of mismatch
detection system in Figure 1, the kind embodied
in ‘comparator models’ of agency (Berti & Pia,
2006; David et al., 2008; Haggard, 2008). If
future findings indicate that the most basic sense
of agency requires such conceptual processes,
then the processes must join the bundle of sensations identified by Hume.
BASIC COMPONENTS OF AGENCY
ACKNOWLEDGMENT
We are grateful for Ryan Howell’s assistance with
every stage of the statistical analysis, and we thank
Amit Etkin for providing unpublished data.
Original manuscript received 1 April 2010
Revised manuscript accepted 1 June 2010
First published online
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