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NEUROCASE 2010, iFirst, 1–22

Cognitive and neural components of the phenomenology of agency

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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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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

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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.


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.



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,

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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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(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


S

S

S

R

S

R

S

R

(A)

(B)

Integrated Action


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’.

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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.

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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).



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.

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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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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).



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).


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



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


13


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).


14

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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,



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-

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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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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.


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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