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Putting the “mental” back in “mental disorders”: a perspective

from research on fear and anxiety
1,2 ✉ 3 4 5,6 7,8
Vincent Taschereau-Dumouchel , Matthias Michel , Hakwan Lau , Stefan G. Hofmann and Joseph E. LeDoux

© The Author(s) 2021

Mental health problems often involve clusters of symptoms that include subjective (conscious) experiences as well as behavioral
and/or physiological responses. Because the bodily responses are readily measured objectively, these have come to be emphasized
when developing treatments and assessing their effectiveness. On the other hand, the subjective experience of the patient
reported during a clinical interview is often viewed as a weak correlate of psychopathology. To the extent that subjective symptoms
are related to the underlying problem, it is often assumed that they will be taken care of if the more objective behavioral and
physiological symptoms are properly treated. Decades of research on anxiety disorders, however, show that behavioral and
physiological symptoms do not correlate as strongly with subjective experiences as is typically assumed. Further, the treatments
developed using more objective symptoms as a marker of psychopathology have mostly been disappointing in effectiveness.
Given that “mental” disorders are named for, and defined by, their subjective mental qualities, it is perhaps not surprising,
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in retrospect, that treatments that have sidelined mental qualities have not been especially effective. These negative
attitudes about subjective experience took root in psychiatry and allied fields decades ago when there were few avenues
for scientifically studying subjective experience. Today, however, cognitive neuroscience research on consciousness is thriving,
and offers a viable and novel scientific approach that could help achieve a deeper understanding of mental disorders and
their treatment.

Molecular Psychiatry; https://doi.org/10.1038/s41380-021-01395-5

INTRODUCTION when behaviorists, because of free-wheeling attribution of mental

Problems related to fear and anxiety are among the most prevalent states as causes of human and animal behavior [28, 29], shunned
forms of mental illnesses [1] and have been the subject of much subjective experience as a scientific construct [30]. The trend
research in animals [2–8] and humans [9, 10]. The success of this continued in the middle of the century, when physiological
pre-clinical research has substantially influenced modern clinical psychologists, mostly from behaviorist backgrounds, began study-
interventions [11–19]. Yet, treatments remain less satisfactory than ing brain mechanisms of overt behavior in animals using the
patients and therapists would like [20–24]. We propose here that methods of behaviorism and embracing its disdain for anything
one factor, more than all others, has contributed to this state of mental [31–34]. Although cognitive science was emerging as a new
affairs: the systematic marginalization of the subjective experience approach to the mind around this time, it treated the mind as a
of patients as a research topic and treatment target. system that processes information rather than one that generates
Modern theories of emotion started in the late nineteenth subjective experiences [35].
century with Charles Darwin [25] and William James [26]. Both Throughout much of the first half of the twentieth century, the
emphasized subjective experience but in different ways. For subjective mind was nevertheless alive and well in psychiatry,
Darwin the mental state of emotion caused behavioral and which was dominated by the psychoanalytic approach initiated by
physiological responses in the body, while for James the body Sigmund Freud. But clinical psychologists in the 1950s and 60s
responses defined the mental state. Contemporary theories of began designing new therapies based on behavioral principles
human emotions, including fear and anxiety, still emphasize the [36, 37]. And biologically oriented psychiatrists were searching
relation between subjective experience, overt behavior, and for medicinal treatments, often through behaviorist-inspired
physiological changes [26, 27]. But the subjective component, studies of animals [38–40]. Proponents of these approaches were
typically assessed via verbal report, has been viewed as no more motivated, in part, by a desire to distance themselves from Freud’s
important than the others, and, in fact, has often been least valued legacy. While they had cause to desire a fresh start, rather than
by scientists. This bias has its roots in the early twentieth century simply distancing themselves from Freud’s view of the mind,

1
Department of Psychiatry and Addictology, Université de Montréal, Montreal, Canada. 2Centre de Recherche de l’Institut Universitaire en Santé Mentale de Montréal, Montreal,
Canada. 3Department of Philosophy, New York University, New York, NY 1003, USA. 4RIKEN Center for Brain Science, Wako, Japan. 5Department of Clinical Psychology, Philipps-
University Marburg, Marburg, Germany. 6Department of Psychological and Brain Sciences, Boston University, Boston, MA, USA. 7Center for Neural Science and Department of
Psychology, New York University, New York, NY 1003, USA. 8Department of Psychiatry, and Department of Child and Adolescent Psychiatry, New York University Langone Medical
School, New York, NY 1003, USA. ✉email: vincent.taschereau-dumouchel@umontreal.ca

Received: 23 April 2021 Revised: 11 November 2021 Accepted: 19 November 2021

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they dismissed the central role of subjective mental states in psychological interventions can be effective treatments because
mental illness. they correct such pathophysiological conditions.
During this same time, the cognitive approach to therapy was This medical perspective gave rise to the commonly used
also emerging in the hands of Albert Ellis [41] and Aaron Beck [42], approach of evaluating the involvement of pharmaceutical and
both of whom were initially trained as psychoanalysts. Their twist other biological targets using behavioral tests in animals before
was to change the focus of subjective distress from unresolved conducting clinical trials in humans. It was assumed that
unconscious conflict to maladaptive beliefs and automatic interventions that proved effective and safe in pre-clinical studies
thoughts. However, over the subsequent years, the popularity of could then be tested in human patients. Because animals lack
the medical model of psychiatry came to be the standard of how the ability to give verbal self-reports of their inner feelings,
to evaluate therapeutic outcomes, and even cognitive approaches behavioral and physiological responses could be used as proxies
began to treat subjective experience as just another factor for subjective experience.
that contributed to the “disease”. As a result, the tendency to But contrary to the predictions of the medical model, decades
marginalize subjective experience is the norm rather than the of research have failed to discover new, efficacious pharmacolo-
exception in the field, despite the fact that the way a patient feels gical treatments [20, 21, 47–49]. As a result, the pharmaceutical
subjectively is a major factor that leads them to seek help, and industry has been eliminating or reducing efforts in psychiatric
also shapes their evaluation of whether the treatment has been drug discovery [23, 24, 50]. According to Steven Hyman [51],
effective. former director of the National Institute of Mental Health, the
Clinicians, of course, have always wanted their patients to failure of the pharmaceutical industry in the area of psychiatric
feel better as a result of their therapies. But because of the research is leading to a global healthcare crisis since psychiatric
inconsistencies they observed in the self-report of patients during illness is the world’s leading cause of disability, and is resulting in
clinical interviews, self-report acquired a bad reputation. As we will enormous societal burden.
see, this was supported by research that questioned the reliability Why has this effort failed? We believe that it was, in fact,
of self-report. But in throwing the baby out with the bathwater, doomed from the start by its commitment to a simplistic view of
important, empirically useful aspects of self-report were ignored. human suffering [52]. Specifically, the medical model of fear
As therapy became more evidence-based, and insurers demanded depends too heavily on the assumption that all three aspects of
objective treatment targets to evaluate treatment success, the fear (subjective, behavioral, physiological) have a common
scientific merit of self-reports was further marginalized (as origin—a fear circuit—in the brain. For instance, the DSM-5
reflected in the NIMH RDoC initiative [43, 44]). describes fear as including “surges of autonomic arousal
In this paper, we propose that the marginalization of subjective necessary for fight or flight, thoughts of immediate danger,
experience in modern psychology, neuroscience, and psychiatry and escape behaviors” ([46], p. 189). This view posits that all
made it inevitable that the treatments developed and implemen- three aspects are manifestations of the same underlying circuits.
ted would be less effective than desirable. Specifically, we suggest Since we humans are assumed to have inherited our “fear
that treatments designed to target easily measurable behavioral circuits” from our mammalian ancestors, interventions that are
and physiological manifestations, while useful for treating effective at normalizing behavioral and physiological proxies in
behavioral and physiological symptoms, are problematic as an rats and mice should be effective in treating fear and anxiety
approach to improving subjective well-being. disorders. To the extent that subjective feelings are also
We will use fear to make our case, and will argue that, contrary troubling, treating the fear circuit should address those, since
to long-standing and current trends, subjective fear is not just fear, like behavioral and physiological responses, is a product of
another factor in the emotion fear; it is what the emotion fear is the fear circuit. As noted above, we do not share this view and
[3, 22, 45]. We believe that the acceptance of this view would suggest that subjective and objective responses be addressed
allow a deeper understanding of the relation of adaptive to separately.
pathological fear and anxiety, and pave the way for new, more
effective, approaches for the treatment of prevalent and troubling Terminological confusion in the study of “fear”
conditions involving these mental states. Fear has received more scientific attention than any other
Before laying out our arguments, it is important to point out emotion. But there have been two conflicting approaches. The
that fear and anxiety, though related, are different states (see [3]). first started with Darwin, who defined emotions like fear as “states
Nevertheless, because these terms have often been used of mind” that we have inherited from our mammalian ancestors
interchangeably in the historical literature, we use the terms by virtue of having inherited some feature of their nervous system
interchangeably when referring to historical points. [25]. This meshed well with the emphasis on consciousness by
both animal and human psychologists in the late nineteenth
century [53]. The second approach began in the early twentieth
THE DISEASE MODEL OF FEAR AND ANXIETY century when the “behaviorists“ called out psychologists for their
Early nosological systems emphasized deep-seated psychody- rampant and often unjustified use of consciousness as explanation
namic conflicts as the latent causes of dysfunction in multiple of behavior.
mental illnesses. Today, the American Psychiatric Association The behaviorists dominated psychology for the next several
[46, p. 20] defines mental disorders, including anxiety disorders, decades. Consequently, the vast majority of researchers in animal
as “a syndrome characterized by clinically significant distur- psychology from the 1920s into the 1960s, and even into the
bance in an individual’s cognition, emotion regulation, or 1970s, were either behaviorists, or trained by behaviorists. Despite
behavior that reflects a dysfunction in the psychological, their disdain for the use of subjective states to explain behavior,
biological, or developmental processes underlying mental behaviorists nevertheless retained the use of subjective state
functioning”. Contemporary classification systems, such as the terms (e.g., fear, hunger) to describe the motivations underlying
International Classification of Disease (ICD-11) and the Diag- behavior. These researchers did not typically mean that a
nostic and Statistical Manual of Mental Disorders (DSM-5), subjective state of fear or hunger was responsible for avoidance
explain “dysfunction” by adopting a medical illness model that of danger or approach to food [54, 55]. Instead, these terms were
assumes that symptoms reflect latent disease entities. In this said to refer to hypothetical intervening variables that connected
perspective, anxiety disorders are a consequence of abnormal stimuli with responses [56]. For example, fear was a functional
brain circuits, neurotransmitters, genes, and/or other biological relation between a dangerous or threatening stimulus and a
abnormalities [43]. It is assumed that pharmacological and/or protective (defensive) response [57–59].

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Meanwhile, biologists studying behavior worked more in the mammalian ancestors in the form of a neural “affect program“ or
tradition of Darwin. One group, the ethologists, opposed the “emotion operating system.” Jaak Panksepp [80, 81], for example,
behaviorist lack of concern with species differences in behavior, used evidence implicating the amygdala and periaqueductal gray
but tended to side with them regarding subjective experience regions of the brain in the defensive behaviors of rats as the basis for
[60]. Another group, physiologists, studied the brain mechanisms postulating that homologous emotion operating systems underlies,
of emotional behavior. The well-known work of Cannon, Bard, not just behavioral and physiological responses, but also the
Hess, Kluver, and Bucy revealed the role of the hypothalamus and subjective experience of fear in rats and humans alike.
temporal lobe in aggressive and defensive behaviors (see [2]). Many working on the circuits underlying defensive behavior in
These researchers were unconstrained by behaviorism and some the behaviorist-oriented physiological psychology tradition at this
freely treated the emotional behaviors they studied as indicators time did not bother to address the issue of what fear meant, since
of subjective feelings of rage or fear. conscious fear was a non-starter, and they just assumed it was a
In the 1950s some behaviorists became physiological psychol- non-subjective physiological amygdala state. Nevertheless, when
ogists. That is, their intervening variables became physiological discussing the implications of behavioral studies in animals for
states in brain areas. This move was inspired by the work of the understanding fear and anxiety as clinical problems, they often
physiologists mentioned above. But physiological psychologists talked about fear in the colloquial way.
mostly remained true to their behaviorist legacy, treating the Because the colloquial way is the way most people, including
physiological factors they studied as non-subjective motivational lay people, journalists, and most scientists not in the fear field,
states, at least initially. think about fear, the public conversation about fear circuits was
The leading behavioral approach for studying “fear” in animal about conscious fear. The result was that the idea of the
psychology from the 1940s through the 1970s was Mowrer’s [61–64] amygdala as the seat of fearful feelings in the brain became a
avoidance procedure ([65, 66] For a review, see [67]). Mowrer cultural meme, one that also implied that drugs or other
proposed that rats are motivated to avoid aversive stimuli (electric treatments that target the amygdala could make people less
shocks) by “fear.” Behaviors that led to successful escape from, and fearful and anxious [18, 82, 83].
later avoidance of, the aversive stimulus were reinforced by “fear”
reduction. An important finding was that early in training heart rate Lang’s three-systems model of fear
rises, but then once the avoidance response is well-established the As a result of the inconsistent use of the term “fear” in the 40s and
rate normalizes [65, 66, 68]. This was interpreted to mean that “fear” 50s, some researchers in the 1960s began to wrestle anew with
leads to the elevation of heart rate. Successful avoidance is then fear as a scientific construct. The work of Peter Lang was
accompanied by a reduction of “fear,” and a decrease in heart rate particularly important.
follows [69]. Lang noted a number of instances in the literature which
Behaviorists like Mowrer treated fear as an intervening variable showed that subjective fear experiences (as measured by verbal
[57, 64]. What did this mean? The natural assumption among reports) did not correlate well with objective and measurable
behaviorists at the time was that fear was a non-subjective state behavioral responses (e.g., avoidance behavior) and physiological
that controls behavior. But as behaviorism became a less changes (e.g., in heart rate) [84–86]. Accordingly, he was critical of
dominant force in psychology, even some behaviorists began to the importance that some clinicians placed on subjective states
speak about “fear” as if they meant subjective fear, using over behavior and physiology.
expressions like “frightened rats” or “rats frozen in fear” [65, 70]. Under the lingering influence of behaviorism and the growing
Often within a single paper “fear” seemed to refer to a non- influence of the new cognitive movement in psychology, Lang
subjective state in some sentences, while in others it seemed to proposed that verbal behavior should be repurposed. Rather than
imply that the animals were subjectively afraid. This was likely as using it as a way to assess intangible subjective experiences, it
much about ideology as about how difficult it is to refrain from should be used to track more tangible cognitive processes.
reverting to the use of an everyday vernacular term for a mental Treatment could then be focused on altering verbal behavior,
state in a non-mental state way. which would, in turn, reflect changes in the underlying cognitive
Some two decades after starting the field, Mowrer clarified his processes, much like the way that treatments that change overt
position, noting that rats freeze and avoid “by-cause of” fear; for behavior or physiological arousal do so because they change
him, in other words, “fear” always meant conscious fear [71]. underlying processes.
Though one could have read this between the lines that he Expressing his scientific distaste for subjective experience, Lang
penned over the years, the field seems to have been blinded to noted: “whether seen as causes or consequences, feelings are
what he was really saying by their ideology. beyond the pale of direct scientific inquiry” ([87], 124). Fear, he
Mowrer’s work not only impacted research on animal behavior said, “is not some hard phenomenal lump that lives inside people”
but also came to be the way that fear was viewed by clinicians. [87]. Instead, it is a response expressed in three response systems:
From the beginning, Mowrer was interested in avoidance learning verbal (cognitive), overt motor, and somatic. The responses
in animals as a tool for understanding pathological human anxiety corresponding with these were self-report for the cognitive
[63]. At that time, Freud’s psychoanalytic approach was the system, behavior (especially avoidance behavior) for the overt
dominant clinical approach, and Mowrer proposed that principles motor system, and physiological changes for the somatic system.
of behavioral learning could improve clinical treatments [72]. Therapy, he argued, should focus on changing the specific
Subsequently, Mowrer’s colleague, Neal Miller, continued this response systems, since each contributes separately to the overall
effort, writing a book called Personality and Psychotherapy with the intensity of fear.
psychoanalyst John Dollard [73]. But by then psychoanalysis was
on the wane, and these efforts, rather than broadening the scope Discordance and desynchrony
of psychoanalytic treatment, paved the way for the emergence of Lang’s, “three-system model” stimulated much clinical research
behavior therapy [36], and then cognitive-behavioral therapy and theorizing [88–94]. While his views had their greatest impact
[41, 74]. Mowrer’s two-factor theory continues to be cited in on clinical research, they also affected basic research in
contemporary clinical understanding of anxiety [75–77]. psychology and neuroscience.
The terminology of fear became even more confusing in the One problem was that Lang’s terminology (cognitive, overt
1970s with the revival of the Darwinian approach adopted by motor, and somatic responses) was a bit unclear. For example,
psychological researchers in guise of basic emotions theory [78–81]. “somatic” is more typically used to refer to skeletal-motor
Fear, in this perspective, was an innate emotion inherited from responses underlying overt behavior than to visceral autonomic

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responses (e.g. [95]). As we proceed we will, therefore, use a more Conceptual challenges
straightforward set of terms: self-report, behavioral, and physio- Given that discordance and desynchrony between responses
logical responses. By “self-report” we specifically mean verbal occur, the key question is whether self-report, behavior, and
reports resulting from conscious fear experiences. Such reports physiology should be interpreted as indicating the existence of
can be interpreted as indicating that the person is having, or has different psychological constructs, or whether they should be
had, a subjective experience of fear in the presence of a interpreted as indications of a single multi-faceted underlying
threatening stimulus or situation. By “physiological responses” construct. This is an issue of construct validity [111].
we mean increases in skin conductance, heart rate or other Construct validation is typically achieved by establishing
visceral changes in the body in response to threatening stimuli or robust correlations between the results of different tests
situations. By “behavioral responses” we mean threat-elicited purporting to measure the same construct. If measures of self-
reactions (freezing, flight), as well as threat-motivated instru- report, physiological activity, and behavioral responses were
mental behaviors (avoidance), expressed in the presence of systematically correlated, it would be relatively straightforward
threatening stimuli or situations [96]. to interpret them as collectively reflecting a single underlying
We will use this terminology to discuss two kinds of construct. However, studies have typically found that self-report
discrepancies in this literature. The lack of concordance between shares only a modest part of its variance with other measures
the three measures of “fear” at a given time is referred to as [112], with the most optimistic estimates indicating about
discordance [90]. There are many examples of discordance in the 27–28% of shared variance [113].
literature [97]. For instance, in the presence of threat, patients There are two main views regarding the interpretation of
have reported high levels of subjective fear, and yet demonstrate discordance and desynchrony in this literature (for an in-depth
normal or even low levels of physiological threat responses (e.g. discussion of these in relation to construct validity in “fear” studies,
heart rate or skin conductance measures), while others show the see [114]). The first attempts to salvage a singular fear construct,
opposite pattern [89, 98–102]. Other forms of discordance have despite the existence of discordance and desynchrony, by arguing
been observed following pharmacological interventions [103]. that self-report, behavior, and physiology are each indicators of
Medications, such as beta-blockers, for example, can dampen the the same underlying construct (fear), but that they differ in the
hyperreactivity of the autonomic nervous system (e.g. heart rate degree of accuracy with which they reflect the construct. The
acceleration) or behavior (e.g., trembling hands, fidgeting) in the second posits that the three factors are independent, but
presence of actual or perceived threats without necessarily interacting, constructs.
affecting the subjective experience of anxiety [104]. Those who favor the first view maintain that using self-reports to
Discordance is distinguished from the phenomenon of desyn- assess fear in effect amounts to using an inaccurate measurement
chrony. The latter refers to variations in the levels of the three procedure. For instance, Fanselow and Pennington (2018) [82, p. 27]
measures over time. For example, a patient undergoing behavioral argue that the amygdala is a “fear generator” that controls all three
therapy for exaggerated fear or anxiety may first show signs of response types, but that the most reliable measures are the
reduced behavioral and physiological symptoms, and gradually behavioral and physiological outputs. They write that “the additional
demonstrate changes in self-reports of fear later on. This was machinery needed to generate subjective report probably adds
reported by Lang in early clinical trials [105]. Another example additional noise, rendering it… a less pure and objective measure of
pertains to the desynchrony between avoidance behaviors and fear.” In this view, cases of discordance and desynchrony are
subjective fear. For instance, the presentation of aversive stimuli explained away as being due to the fact that self-reports are the
often generates both avoidance behaviors and subjective reports least accurate of the three measures of fear [58, 82, 115]. According
of fear. But, successful avoidance will typically lead to a decrease to Fanselow and Pennington (2018), emphasizing the subjective
in fear reports while avoidance behaviors can persist over experience of fear will “push us back well over a century to what was
extended periods of time [106]. truly the dark ages of psychiatry” (p. 28).
Cases of discordance and desynchrony emphasize that beha- In contrast, those who favor the second view posit that cases of
vioral and physiological responses that are sometimes correlated discordance and desynchrony indicate the existence of separate
with subjective fear should not necessarily be interpreted as factors. For example, LeDoux and colleagues [21, 116–118] argue
indicating that the person is consciously experiencing subjective that while behavioral and physiological responses elicited by
feelings of fear per se [54, 55, 107]. In fact, for the sake of clarity, threats are products of the amygdala, subjective fear reflects a
if nothing else, we maintain that the mental state term “fear” cognitive interpretation that one is in a situation of potential or
should be reserved for the mental state, and behavioral and actual psychological or physical harm. Such an approach is hardly
physiological responses should be referred to as “threat” or a fringe idea, as cognitive theories are leading explanations of
“defense“ responses. emotions [119–121]. Recently, the higher-order theory (HOT) of
Considerable confusion in the discordance and desynchrony consciousness (see Box 1; [122]), which is usually discussed in
literature has also resulted from a failure to recognize that in relation to visual perception, has been extended as a novel
threatening situations a variety of behaviors can result [96]. cognitive account of fear and other emotions [116, 123, 124].
Species-typical (innate) reactions (e.g. freezing behavior) are According to HOT, consciousness arises when higher-order
automatically elicited by unlearned or conditioned stimuli, while cognitive structures monitor or meta-represent lower-order
instrumental responses (e.g. avoidance) are acquired by their information (see Fig. 1). A simple version of the higher-order
consequences and are emitted in appropriate situations. Species- account would be that signals resulting from the consequences of
typical reactions to unlearned or conditioned stimuli have reliable the behavioral and physiological responses generated by the
physiological correlates that are “wired in” as part of the “defense amygdala in the brain and body are re-represented and contribute
reaction” [108], but most avoidance and other instrumental to the experience of fear. But the model also includes emotion
responses do not, since these can be achieved in many ways schema and self-schema, as well as meta-representations of
[109]. This may account for the poor correlation often observed semantic and episodic memories. These representations result in a
between physiological measures and avoidance behavior [106]. mental model of the dangerous situation, which can fully account
Furthermore, instrumental avoidance responses, though often for the subjective experience of fear, even in situations where the
treated as a single class of response, can be due to habit learning, amygdala activity and body feedback are absent. That this is
goal-directed action learning, or cognitive deliberation, each of necessary is clearly indicated by discordance and desynchrony
which involves different neural circuits [96, 110]. Future studies between subjective fear and body arousal. Antonio Damasio [125]
should adopt a more subtle approach to behavioral measures.

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indicating that humans sometimes exhibit surprisingly poor
Box 1. First-order theories vs higher-order theories capacities for self-knowledge (for a review, see [130]). This
In consciousness science, one core topic of disagreement pertains to the origin of evidence could be interpreted as suggesting that subjective
consciousness in the brain. Here, when we say consciousness, we refer to what is reports are systematically inaccurate, and are, therefore, unreliable
sometimes called phenomenal consciousness, that is the qualitative or phenom- scientific tools.
enal “feel” of experiences. For example, looking at a sunset has a subjective
character that can be described in terms of “what it feels like”. This is different
However, alleged cases of unreliability are not cases in which
from what can be called states of consciousness which are studied, for instance, in subjects report about ongoing conscious experiences, but instead
minimally conscious patients or sleep. While undoubtedly important, especially for are typically cases in which participants report about the causes of
clinical practices, the study of states of consciousness does not directly address the their behaviors [128], or about long-standing psychological
question of how the brain generates this subjective “feel” of things.
While many theories of phenomenal consciousness make vastly different
attitudes such as their beliefs [130]. Aside from pathological cases
predictions from one another [156], they can be broadly divided in two categories. (e.g. Anton’s syndrome), or malicious deceit, there is no significant
First-order theories, such as recurrent processing theory [157–160], posit that body of empirical evidence to support a general dismissal of
consciousness originates in brain regions specialized in the processing of a given subjective reports about conscious experiences such as perceptual
type of information (for instance, visual or auditory cortices). As we saw in the main
text, some authors have suggested that the amygdala might be such a first-order
experiences, fear or anxiety [131, 132]. As a matter of fact, a wide
structure in the subjective experience of fear [81, 82, 161]. Another first-order variety of experiments in fields, such as perceptual psychology
theory, the global neuronal workspace theory, posits that the activity within first- [133], and even more germane, the scientific study of emotions
order structures becomes conscious when it is made available to other brain regions [134], rely on experimentally controlled subjective reports about
through a global broadcasting mechanism.
On the contrary, higher-order theories suggest that these first-order structures
what the subject experiences.
may not be sufficient for the information to become conscious [122, 162, 163]. They According to Borsboom et al.’s [135, p. 1061] definition of
posit that some additional cognitive processes in other regions may be needed in validity, “a test is valid for measuring an attribute if and only if (a)
order to monitor the information. In this perspective, subjective experience arises the attribute exists and (b) variations in the attribute causally
from a mechanism closely related to metacognition, which also involves the
monitoring of one’s own cognitive and sensory processing [164]. As such, the
produce variations in the outcomes of the measurement
information represented in first-order structures should remain unconscious if no procedure”. Given that self-reports can be interpreted as resulting
higher-order processing is involved. With respect to fear, this view posits that the from variations in metacognitions (cognitive re-representations)
amygdala non-consciously controls defensive behavioral and physiological that are directly antecedent to the experience of fear, it follows
responses to threats, but that higher-order processes are required in order to
generate the subjective experience to the same threatening stimulus
that self-reports are valid indicators of fear experience. On the
[54, 55, 107, 116, 163]. In this view, the re-representation of the first-order other hand, since behavior and physiology can sometimes
information (often termed as meta-representation) is a non-conscious antecedent dissociate from the feeling of fear, interpreting them as reliable
to consciousness. We suggest that treatment strategies that target both the indicators of fear, if we follow Borsboom, is invalid, though not
subjective (conscious experience) and objective (behavioral and physiological
responses) will be more effective than approaches that primarily focus on objective
necessarily useless.
responses. We also suggest that measures of discordance and desynchrony can These observations are in line with the second interpretation of
provide additional indicators of treatment progress. discordance and desynchrony in fear research discussed above. As
such, we hold that behavior and physiology, on the one hand,
result from threat detection and the activity of defense mechan-
isms, while self-report, on the other hand, results from the
metacognitions upon which subjective experience is based. It
follows that self-report, which reflects these metacognitions as
well (Fig. 1), is the only valid indicator of fear as a subjective
experience.

Clinical pragmatism
In addition to its scientific merits, our view of the subjective fear
construct is consistent with the way patients express their
concerns in clinical settings, and is often what they care most
about. From a clinical perspective, a problem usually only reaches
the level of clinical significance if it is associated with significant
subjective distress and/or interferes with the person’s life. Without
the subjective experience of distress, it is very difficult to conclude
Fig. 1 Discordance and desynchrony in light of a higher-order that an individual suffers from an emotional disorder. This is why
perspective. Threatening stimuli often lead to subjective fear via the subjective distress is a core feature of the definition of an
higher-order circuit, and trigger bodily reactions (behavioral and emotional disorder (e.g., in the DSM-5). From this perspective, self-
physiological responses) via the defensive survival circuit, in parallel. report is the most direct measure of the patient’s problem and
This higher-order model can account for situations where subjective treatment efficacy. Thus, whether implicit or explicit, the
and objective responses are discordant or desynchronous. For
instance, blocking physiological reactions (X1) dissociates them
subjective experience of the patient has been the focal point of
from conditioned or forecasted actions and/or conscious experi- all mental disorders, especially emotional disorders.
ences, while blocking physiological reactions (X2) dissociates those At the same time, self-report data rarely determine the clinical
from behavior reactions and/or conscious experience. Similar logic status directly. Instead, the patient’s subjective report is filtered
applies to X3 and X4. ANS autonomic nervous system. and interpreted by a clinician to derive a clinical assessment. This
is in part because clinicians have long recognized that relying
only on self-report in their clinical assessment presents some
similarly noticed this and proposed “as if body loops” that limitations. As we discussed in the “Conceptual challenges”
simulate brain and body activity when these are absent. section, self-report about recalled causes of past behaviors [128]
The controversy surrounding the two perspectives is in part or about beliefs [130] can sometimes be misleading. Such
fueled by the long and complex history of subjective reports observations, together with the influence of the behaviorist
[29, 126]. For instance, some social psychologists have suggested movement, fueled a general trend in psychiatry research to look
that self-reports about the causes of our own actions are for objective (behavioral and physiological) markers of pathology.
often mistaken [127, 128]. The use of self-reports has also been For instance, although the Research Domain Criteria initiative
criticized in other disciplines, such as sociology [129], thus (RDoC) of the NIMH (the National Institute of Mental Health in the

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United States) [43, 44] purports to recognize the importance of Once individuals are identified as having higher degrees of
human psychology, its view of self-report is ambivalent at best: discordance and/or desynchrony, it would be possible to examine
“experiential claims represent a kind of “folk” psychology of the how their brain’s structure and physiology might be associated
self that should [not be] assumed veridical.” It also acknowledges with such variations. In Taschereau-Dumouchel et al. (2020) [142]
that these claims should not be “simply discounted” [44, p. 292]. we identified brain regions that are specifically important for
As such, the ultimate goal in psychiatry research in modern times decoding self-report vs physiological responses to threat. Studying
has chiefly been to identify biological markers of mental disorders, the connectivity between these different regions—as assessed by
akin to other medical diseases. structural imaging based on diffusion, or resting-state fMRI data—
Some have resisted this trend and advocated for the may also predict individual differences in discordance and
importance of subjective reports [136–138]. For instance, Edna desynchrony [145, 146]. Similarly, machine-learning algorithms
Foa [139], a leading clinical researcher, noted that self-report trained to predict self-report, physiology and behavior [142, 149]
generates “valid measures of key constructs, some of which could also help us reveal the brain mechanisms associated with
cannot be measured in any other way, and sometimes are the best discordance and desynchrony. Studying such individual differ-
measure of the construct of interest”. Similarly, we [3, 21, 55] and ences in brain processes might therefore help us better under-
others [45] argued that emotions are first and foremost subjective stand how discordance and desynchrony are associated with
experiences. As a result, self-report should play a significantly pathological conditions.
more prominent role in clinical practice. It can be collected As such, distinguishing between the three measures might have
through clinical interviews, daily diaries, in vivo exposure, great clinical benefits. At the same time, we should not lose sight
computerized tasks, or using virtual reality approaches. And given of the fact that they are related constructs, in part because they
that we now have better understanding of the various factors that are consequences of the same external stimulus. And although
affect the validity and reliability of self-report, we can work toward the brain processes underlying each are separate, they interact.
improving clinical tools, paving the way for more rigorous and
valid assessments of subjective experience in clinical practice. Moving forward
By distinguishing between physiological, behavioral, and self- To this day, the role of subjective experience in leading theories of
report measures, fear and anxiety research can use valid and emotions remains marginalized. Basic emotions theorists have
reliable procedures for addressing each of those constructs when tended to emphasize the facial expression of emotions, and to a
needed. For instance, unlike physiological responses, subjective lesser extent, autonomic responses to a greater degree than
ratings during an extinction procedure (i.e., expectancy of the subjective experiences [79, 150]. Cognitive appraisal theorists give
unconditioned stimulus) are predictive of post-exposure affective more weight to subjective experience than basic emotions theories,
ratings, a clinically meaningful measure associated with the but they typically treat it as one component among several that
relapse of fear [140]. Importantly, this association was observed collectively constitute an emotion [151]. Cognitive construction
even though subjective ratings were also correlated with theories, on the other hand, respect the centrality of subjective
physiological responses at various stages of the experiment. experience, and treat it as a conceptualized byproduct of valence
Furthermore, another line of evidence comes from a recent meta- and arousal [152]. Our higher-order theory is, in some sense,
analysis indicating that psychotherapy and pharmacotherapy may constructionist and conceptual in nature, but it has a broader view
have very different effects in the brain [141]. More precisely, the of the non-conscious precursors [107, 116, 118, 123, 145, 153] and it
results suggest that psychotherapy might target cognitive highlights the idea that the conscious experience is the emotion
processes and schema in the prefrontal cortex while antidepres- (also see [45]).
sant medication might primarily affect the amygdala and basal Considering the marginalized role of subjective experience in
ganglia. As we saw above, there are reasons to believe that emotion research, and the fact that objective measures of
objective measures may primarily originate from the defensive physiology and behavior are relatively poor indicators of
survival circuit that includes the amygdala while the subjective subjective suffering, we [3, 21, 55] and others [45], have felt
experience is likely generated by the higher-order circuit that compelled to raise concerns. In some related fields, this issue has
includes the prefrontal cortex [141–143]. As such, these examples long been taken seriously. For instance, in the study of pain, self-
highlight the added values of considering the three constructs report is the traditional gold standard in part due to well-known
separately as they each provide distinct information and may cases of discordance (see [154]), not unlike those we emphasized.
require different treatment strategies. But research on many mental health disorders has unfortunately
Furthermore, by studying how discordance and desynchrony not generally benefited from a similar epiphany. With discussions
between the three measures naturally occur it may be possible to about other disorders also emerging [155], we think that the time
tailor therapies to the individual needs of patients [21, 144–146]. is right for a change.
This idea was notably put forward some time ago by Rachman [89] Progress in the scientific study of consciousness, and recent
and Michelson [100] who suggested that behavioral therapy may work applying this knowledge to explore emotional conscious-
be particularly effective if a patient has exaggerated behavioral ness, opens the door for a new beginning for designing
or physiological responses, but low levels of self-reported fear. treatments that will hopefully better target subjective aspects of
Such “tailored” approach must however be used with caution as mental disorders. To succeed, though, this will require a
treating exclusively the objective response systems may lead the reassessment of some of the implicit assumptions of the
subjective system to relapse, and vice versa [21]. behaviorist and medical model legacies, both of which linger as
Early reports also revealed gender differences in discordance and sources of unconscious inferences that guide research and theory.
desynchrony [147]. In some situations, men showed lower self- However, we are confident that the approach we tout will lead to
reported levels of negative emotions compared to women even new interventions, including personalized ones, capable of
when their physiological responses were high [148]. As one can tackling mental health disorders in a more complete fashion.
imagine, effects like these may well be modulated by age and
cultural factors. If we can track what the systematic factors
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