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Mental Pain, Boredom, and Diffuse Nociception

November 2024
Psychology of Consciousness: Theory, Research, and Practice

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New York University

In this article, I propose a novel theory to explain the possible physiological origins of the relatively mild mental pain that is often labeled as boredom and possibly loneliness or a negative mood, depending on one’s situation. My admittedly speculative hypothesis is that most people in modern societies are beset by a chronic level of diffuse nociception (DN), due to the lingering effects of past stressors. For most people, most of the time, their DN is mild enough to be kept out of conscious awareness by various distractions. However, when people are deprived of all their usual distractions, DN may enter awareness and provoke a feeling of pain without being associated with any noticeable bodily sensation to which the pain can be localized. Thus, the discomfort is experienced as mental pain. It follows that whatever can reduce DN and/or keep it out of awareness will be positively reinforced, leading to an addiction to various distractions, including mind wandering. In support of my theory, I discuss research on how the activity of well-known neural networks serves to regulate the intensity of physical, as well as mental, pain. I also discuss individual differences in DN and their relationship to boredom proneness and neuroticism. Finally, I describe how stress reactions can create DN, how psychological factors can mitigate mental pain, and how chronic stress reactions may begin early in human development.

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Psychology of Consciousness: Theory, Research,

and Practice

Mental Pain, Boredom, and Di󰍎use Nociception

Barry H. Cohen

Online First Publication, November 21, 2024. https://dx.doi.org/10.1037/cns0000405

CITATION

Cohen, B. H. (2024). Mental pain, boredom, and di󰍒use nociception. Psychology of Consciousness: Theory,

Research, and Practice. Advance online publication. https://dx.doi.org/10.1037/cns0000405

Mental Pain, Boredom, and Diffuse Nociception

Barry H. Cohen

Department of Applied Psychology, Steinhardt School of Culture, Education, and Human Development,

New York University

In this article, I propose a novel theory to explain the possible physiological origins of the

relatively mild mental pain that is often labeled as boredom and possibly loneliness or a

negative mood, depending on one’s situation. My admittedly speculative hypothesis is

that most people in modern societies are beset by a chronic level of diffuse nociception

(DN), due to the lingering effects of past stressors. For most people, most of the time, their

DN is mild enough to be kept out of conscious awareness by various distractions.

However, when people are deprived of all their usual distractions, DN may enter

awareness and provoke a feeling of pain without being associated with any noticeable

bodily sensation to which the pain can be localized. Thus, the discomfort is experienced

as mental pain. It follows that whatever can reduce DN and/or keep it out of awareness

will be positively reinforced, leading to an addiction to various distractions, including

mind wandering. In support of my theory, I discuss research on how the activity of well-

known neural networks serves to regulate the intensity of physical, as well as mental,

pain. I also discuss individual differences in DN and their relationship to boredom

proneness and neuroticism. Finally, I describe how stress reactions can create DN, how

psychological factors can mitigate mental pain, and how chronic stress reactions may

begin early in human development.

Keywords: boredom, mental pain, nociception, mind wandering, stress

Nociception refers to the process whereby

specialized sensory receptors, called nociceptors,

distributed throughout the skin, the skeletomus-

cular system, and the viscera, are triggered by

physical stimuli potentially harmful to the body

and then send neural signals toward the brain.

Much is now known about the nerve pathways

that carry these signals and how they are

processed and modulated along the way.

However, whereas these signals are generally

capable of producing some conscious experi-

ence of pain, there are a host of psychological

factors that inﬂuence the perceived intensity

and unpleasantness caused by these noxious

sensations.

Damage or extreme stress to a particular part of

the body can produce a highly localized experi-

ence of physical pain. However, I will propose in

this article that relatively mild nociception arising

diffusely from several areas of the body at once,

possibly including both skeletal muscles and the

viscera, can lead to a general level of discomfort

that is perceived as mental or psychological pain.

If the unpleasantness of this stimulation cannot

be subjectively localized to the body, it can easily

be attributed to a feeling or mood arising from

Barry H. Cohen https://orcid.org/0000-0002-6241-

1927

Barry H. Cohen is now at Greenwich, Connecticut, United

States.

The author has no known conﬂicts of interest to disclose.

This work is licensed under a Creative Commons

Attribution-Non Commercial-No Derivatives 4.0 International

License (CC BY-NC-ND 4.0; https://creativecommons.org/

licenses/by-nc-nd/4.0). This license permits copying and

redistributing the work in any medium or format for

noncommercial use provided the original authors and source

are credited and a link to the license is included in attribution.

No derivative works are permitted under this license.

Correspondence concerning this article should be

addressed to Barry H. Cohen, 47 Lafayette Place,

Greenwich, CT 06830, United States. Email:

barry.cohen@nyu.edu

Psychology of Consciousness:

Theory, Research, and Practice

ISSN: 2326-5523 https://doi.org/10.1037/cns0000405

one’s situation (e.g., boredom if one feels stuck

performing a monotonous task).

Any external sensory stimulation and/or motor

activity that has the consequence of reducing this

mental pain will be positively reinforced and can

therefore easily become psychologically addictive.

In Dopamine Nation,Lembke (2021) explained

how people in modern societies are quickly getting

addicted to the secretion of dopamine associated

with various pleasurable activities. My theory adds

to that framework by suggesting that a chronic low-

level of diffuse nociception (DN) makes most

people that much more susceptible to addiction due

to the avoidance of mental pain that these addictive

activities and experiences provide.

The Two Components of Physical Pain

It has long been recognized that physical pain

has two distinct dimensions; Melzack and Casey

(1968) formalized this notion by referring to them

as sensory and motivational-affective. Modern

pain research is based on this distinction. Price

et al. (1987), for example, asked their participants

to rate their pain on two separate visual analog

scales, one for the level of pain sensation intensity

and one for the degree of unpleasantness. They

found important differences in the relative intensi-

ties of the sensory and affective components of

bodily pain according to the participant’sinterpre-

tation of their situation (e.g., given equal levels of

painintensity,womenfocusingonthebirthoftheir

baby rated their labor pains as less unpleasant than

those who focused mainly on their pain). Other

studies have shown that pain of a given intensity is

less aversive if it can be predicted (Ploghaus et al.,

2003)orcontrolled(Wiech et al., 2006).

In fact, in some special circumstances, the

sensory dimension of pain can be felt with little or

no unpleasantness. That physical pain has two

distinct components can be seen most clearly

when one component appears in the absence of

the other. An extreme example that illustrates the

separability of the two pain dimensions occurs in

the case of congenital indifference to pain, or pain

asymbolia (Nagasako et al., 2003). Those suffering

from this anomaly frequently injure themselves

because they do not experience any immediate

motivation to withdraw from a stimulus damaging

their body. A somewhat similar indifference to pain

was produced in the early days of psychosurgery

by means of a prefrontal lobotomy. Fortunately,

that crude, highly destructive procedure has been

replaced by a much more speciﬁc operation in

which only portions of the anterior cingulate cortex

(ACC) are bilaterally ablated; thus, it is referred to as

a cingulotomy (Wang et al., 2017). Used as a last-

resort treatment for chronic debilitating pain, its

effects were described on the Columbia University

Neurosurgery (n.d.) website in the following way:

“Cingulotomy targets the ‘bothersome’aspect of

pain. Although not all patients are completely free

of pain after the procedure, many report feeling less

anxiety and less distress from any pain that remains”

(https://www.neurosurgery.columbia.edu/patient-

care/treatments/cingulotomy). Temporary indif-

ference to pain can be produced by various drugs,

but it is especially pronounced upon inhaling

nitrous oxide, which can produce a dramatic

dissociation between the sensory and aversive

dimensions of pain (Chapman et al., 1943).

A dissociation between the two dimensions of

pain occurs in the opposite direction in hyper-

algesia (the aversiveness of pain far exceeds what

could be expected from relatively mild nociceptor

stimulation) or allodynia (pain produced by

nonnociceptive stimuli; Jensen & Finnerup,

2014), but it is not clear if the aversive dimension

of pain can occur without any associated bodily

stimulation.

Is Mental Pain the Same as the Affective

Component of Physical Pain?

The concept of mental pain has received

considerable attention recently because of its close

association with depression and suicidality. In this

clinical context, mental pain is deﬁned largely by its

severity. It is notable that when mental pain is severe

enough, the sufferers of it often describe it in a way

that implies that their mental pain is essentially the

same as the painful component of bodily pain but

more intense, even though it cannot be attributed to

a bodily location. To illustrate this concept, Mee et

al. (2006) presented several quotes from severely

depressed patients who had attempted suicide, such

as: “I have suffered from severe, recurrent depre-

ssion for 40 years. The psychological pain that I felt

during my depressed periods was horrible and more

severe than my current physical pain associated

with metastases in my bones from cancer”(p. 682),

and “The pain from my recent episode passing a

urinary stone did not compare in severity to the pain

and suffering I experienced during my depression

when I was so intensely suicidal”(p. 682).

2 COHEN

The concept of mental pain is compelling in the

case of profound grief and severe depression,

given the types of descriptions I just quoted. In

those cases, the pain is strong enough to stand out

from any other feeling. However, I propose that

just as bodily pain can be mild or severe, mental

pain, whether or not it is accompanied by a

noticeable bodily sensation, can also be mild as

well as severe. To answer the question posed by

the title of this subsection, experiences described

as mental pain may be occurrences in which the

cerebral activity underlying the unpleasant

dimension of pain is evoked solely by psychological

causes, such as social or romantic rejection, rather

than bodily nociception. Biro (2010) expressed this

possibility thusly:

If tissue damage is not necessary to feeling pain and if

there is a special affective center in the brain devoted to

such feeling, why can’t that center be activated by means

other than the nociceptor pathway? Why isn’t it possible

that noxious psychological stimuli—stimuli that

threaten the emotional well-being of a person, like the

loss of a child or the pain of depression or the suffering

of cancer patients—ﬁnd their way to the anterior

cingulate gyrus, making us feel the same way we do

when we experience physical pain? (p. 663)

I will revisit the question posed by this section

in the context of a deep dive into the neural

mechanisms underlying the experience of pain

later in this article.

Is All Pain Mental Pain?

When the sensory component of bodily pain

occurs withnone of the affective component—that

is, if there is no unpleasantness to it—does it really

make sense to call it “pain”?Ontheonehand,it

seems contradictory to say that the pain someone

felt while inhaling nitrous oxide, for instance, was

not painful. On the other hand, it seems perfectly

legitimate to state that severe cases of grief or

depression are painful, even in the absence of any

sensation normally associated with bodily pain.

This realization leads logically to the notion that

all pain is mental. As Joffe and Sandler (1967)

expressed it, pain should be deﬁned broadly as:

…consisting essentially of an unpleasant feeling quality

which may be associated with a wide range of ideational

content. Pain referred to the body can then be seen as a

particular instance of pain in which the ideational content

refers to the idea, correct or otherwise, of body damage.

Our general view of pain is that it should not be

restricted to the particular feeling quality associated with

bodily pain, but that it is a general element in all

unpleasant feeling states. (Emphasis in original, p. 71)

Although all pain can be said to be mental, for

clarity, I will adopt the convention of using the

term physical pain for instances in which pain

appears subjectivelyto be coming from a particular

bodily location and mental pain when there is no

associated bodily sensation. I will also use the term

psychological pain when mental pain appears to

have a speciﬁc psychological cause, as in the case

of social rejection.

Conceptualizing Boredom as a Form of

Mental Pain

The subjective experience known as boredom

is almost universally identiﬁed with a negative,

aversive feeling that one wishes to escape (Goetz

et al., 2014). In that sense, boredom fulﬁlls the

deﬁnition of mental pain, and, in its milder form,

it appears to be a good example of pure mental

pain (i.e., not colored by speciﬁc emotions).

However, recent research, of which there is a

great deal, has been focused mainly on determin-

ing the particular conditions that can produce

subjective reports of boredom in a laboratory

environment, such as having participants perform

tasks that are very easy and inherently uninter-

esting or tasks that are frustratingly difﬁcult

(Westgate & Wilson, 2018). Little research has

touched on the physiological basis of the mental

pain usually associated with states of boredom.

My main question with respect to boredom is:

How does a boring situation lead to activation of

brain activity associated with mental pain? Given

how common and unpleasant experiences of

boredom can be, I believe this is a question worth

addressing. One avenue for understanding the

aversive nature of boredom is to view boredom as

arising from the thwarting of an inherent drive,

analogous to depriving a person of food.

The Exploratory Drive

Boredom has a distinct motivational aspect,

which has led psychologists to theorize that it

likely serves a useful, or even vital, purpose—one

that has had an adaptive advantage through the

course of evolution. Bench and Lench (2013)

explained the main function of boredom thusly:

Boredom should encourage the pursuit of goals and

experiences that differ from those currently experienced.

MENTAL PAIN AND DIFFUSE NOCICEPTION 3

In many cases, this would come in the form of novel

stimulation which would introduce opportunities for

cognitive and social growth, even if the alternative

situations might elicit negative emotion. That is, by

creating a desire for change, boredom encourages people

to alter their current situation, which permits the attainment

of opportunities that might have been missed. (p. 464)

It is a commonplace observation that various

members of the animal kingdom, especially

mammals, have what is often described as an

exploratory drive, along with a need for novel

stimulation. Moreover, animals can seem to be

bored by monotonous surroundings. For exam-

ple, Meagher and Mason (2012) found that minks

housed for months in impoverished cages later

responded to all types of stimuli more quickly

than minks that had been housed instead in

enriched cages.

It is easy to see why a need for novel stimulation

would be selected for by evolution. Thus, it is

understandable that humans would share that

need and be especially aware of an urge toward

changing their environments and/or trying new

activities when faced with a monotonous and

unproductive situation. When thwarted, that urge

could be expected to give rise to an uncomfortable

feeling, much like the deprivation of food causes

hunger. The pain of a thwarted drive can be

viewed as a form of mental pain, and its subjective

nature suggests a commonality with physical pain.

The Neurophysiology of Pain

Pain as a Homeostatic Emotion or Drive

According to Craig (2003), pain in humans is

“… an emotion that reﬂects speciﬁc primary

homeostatic afferent activity”(p. 304). In Figure

1, Craig (2003) illustrated the major pathways

that carry nociceptive signals to the brain and

ultimately lead to the unpleasant motivational

aspect of pain. Neural impulses travel up the

lateral spinothalamic tract, innervating the para-

brachial nucleus and the periaqueductal gray area

(PAG) in the brainstem, before relaying in two

medial nuclei of the thalamus. The ventral medial

nucleus sends highly speciﬁc information to the

insular cortex, while the medial dorsal nucleus

sends more integrated homeostatic information to

the ACC. This is the brain structure whose ablation

is called a cingulotomy, and, as mentioned

previously, its destruction can greatly reduce the

aversiveness of physical pain.

Working with a large database of functional

magnetic resonance imaging (fMRI) ﬁndings,

Lieberman and Eisenberger (2015) implicated the

dorsal ACC (dACC) speciﬁcally as the critical

area for pain processing. However, they concep-

tualized the dACC more broadly as mediating

negative affect and serving the role of a neural

alarm system warning the higher cortical areas that

“… hardwired survival-relevant goals are [being]

threatened, including those that do not involve

nociception”(p. 15254). These survival-relevant

goals include hunger, thirst, and breathlessness (air

hunger), and Lieberman and Eisenberger present

some evidence that conﬂicts involving these

goals also activate the dACC. As an example of

a survival-relevant goal that does not directly

involve nociception, they offer social rejection,

which has often been found to be associated with

dACC activity.

The Salience Network

The focus of much brain-scanning research in

the last couple of decades has been on neural

networks, which consist of interconnected corti-

cal areas that tend to activate together under

reproducible conditions. This research has reli-

ably identiﬁed three major neural networks in

participants at rest: a central executive network; a

default-mode network (DMN); and a salience

network (SN; Goulden et al., 2014;Seeley et al.,

2007;Sridharan et al., 2008). I will discuss the

ﬁrst two in a later context, but it is the SN that is

especially relevant to pain. The major hubs of the

SN are the dACC and the anterior insula (AI; or

the larger frontoinsular cortex). The SN also

includes the amygdala and areas in the brainstem.

The name of this network comes from its

activation by salient stimuli, and you will notice

that it includes the brain areas that respond to

pain, which have been referred to as the “pain

matrix”(Legrain et al., 2011).

As would be expected, nociceptive stimuli

trigger the attention-getting activity of the SN.

However, it can also be expected that the SN will

be activated by interference with nonnociceptive

survival-relevant goals, such as social afﬁliation,

which also involve threats to the well-being of the

organism. From that perspective, the need for

novelty and exploration could be considered a

nonnociceptive survival-relevant goal, such as

social afﬁliation, and when a conﬂict with that

4 COHEN

goal arises, the dACC and other parts of the SN or

pain matrix may be activated.

The Overlap of Neural Activity Subserving

Both Physical and Psychological Pain

The pain of social or romantic rejection is a

good example of a feeling that is experienced

mainly as psychological pain, even though brain-

scanning research has shown that there is a great

deal of overlap in the patterns of cortical activity

associated with social pain and physical pain that

includes brain areas that play a major role in

processing bodily pain (see Eisenberger, 2012,

for a review). Summarizing their results, Kross et

al. (2011) wrote:

Here we demonstrate that when rejection is powerfully

elicited—by having people who recently experienced an

unwanted break-up view a photograph of their ex-

partner as they think about being rejected—areas that

support the sensory components of physical pain

(secondary somatosensory cortex; dorsal posterior

insula) become active. (p. 6270)

These ﬁndings can help to explain the physical

metaphors often used to describe the pain of

romantic rejection, such as heartache. However,

despite the extensive overlap on a macro level,

Woo et al. (2014), using multivariate pattern

analysis, were able to discriminate the neural

activity evoked by social rejection from that

evoked by painful heat. Woo et al.’s research was

directed at the theory that, through evolution,

social rejection came to activate the physical pain

system as a means to ensure that social animals

would not casually risk the serious dangers of

social isolation. Their research demonstrated that

social rejection does not activate the same exact

neural areas as painful heat applied to the surface

of the body, though they did show activation of

adjacent areas in the same anatomical brain

regions. Notably, Woo et al. do not attempt to

explain why social rejection should evoke

activity in any parts of the insula or somatosen-

sory cortex, which are strongly associated with

bodily perception (i.e., interoception).

The ﬁndings of Woo et al. (2014) do call into

question whether the mental pain of social

rejection is the same as the aversive component

of physical pain. As a working assumption, I will

adopt a simple form of mind–brain identity theory

that proposes that distinguishable subjective

experiences must correspond to distinct patterns

of brain activity and vice versa. In that case, Woo

et al.’s results imply that social pain is not identical

to the aversive feeling of physical pain. However,

both social rejection and bodily harm activate the

SN broadly and narrow the focus of consciousness

to deal with the perceived threat. It may be this

overall mobilization of the brain that is aversive

and is perceived as a “painful”experience, rather

than the activation of speciﬁc neurons. I will

present psychologicalevidence in a later section to

support this general notion. First, it is important to

acknowledge the critical role of the prefrontal

cortex in creating the experience of pain.

The Role of the Prefrontal Cortex

Though activation in the dorsal part of the ACC

has been shown consistently to play a major role

in the production of the aversive aspect of pain,

there is solid evidence suggesting that the dACC

has its effect on the unpleasantness of pain

through its neural projections to the medial

portion of the prefrontal cortex (mPFC). If this is

the case, it could be predicted that any experi-

mental manipulation that increases the aversive-

ness of a painful stimulus without increasing the

intensity of the sensory input ought to lead to

increased activity speciﬁcally in the mPFC. This

hypothesis was conﬁrmed in a study by Bräscher

et al. (2016), who compared controllable and

uncontrollable thermal stimulation while parti-

cipants continuously rated their pain intensity in

an fMRI scanner. As compared to controllable

pain, uncontrollable pain was associated with

greater connectivity between the mPFC and both

the AI and parts of the ACC. The authors suggest

that the mPFC may actually be increasing

nociceptive processing in the insula and ACC

as a result of an increased emotional reaction to

the uncontrollability of the painful stimulation.

They also found that the dorsolateral prefrontal

cortex appeared to be decreasing activity in the

insula and thalamus during controllable pain,

suggesting that the controllability allowed for

downregulation of pain processing.

To be more speciﬁc about the part of the mPFC

that is most associated with the unpleasantness of

pain, Jahn et al. (2016), in a fMRI study using

electric shocks as aversive stimuli, found pain

processing to be localized to the more ventral

region of the mPFC (ventromedial prefrontal

cortex). A very recent review of brain-scanning

research on chronic pain patients by Johansson

et al. (2024) came to an even narrower

MENTAL PAIN AND DIFFUSE NOCICEPTION 5

localization of an mPFC area that may be

responsible for cognitive and evaluative responses

that exacerbate the aversive quality of pain:

We suggest that increased dorsal vmPFC activity may

reﬂect a tendency to overthink the meaning of pain for

oneself and one’s actions. This may in turn increase the

personal threat of a given context and thereby increase

the susceptibility to experience pain, which we suggest

might be reﬂected by an increased functional connec-

tivity between the dorsal vmPFC and the AIC [anterior

insular cortex]. (p. 8)

A Proposed Physiological Basis for the Pain of

Boredom

Earlier, I described one possible theory for

explaining the unpleasantness of boredom: That

the aversive state known as boredom occurs when

a drive, such as the exploratory drive, is blocked

by one’s circumstances, resulting in the activation

of the salience/pain network. Boredom research-

ers have suggested a causal role for the impeding

of other, more speciﬁcally human, drives, such as

a need to pursue a meaningful goal or to reach an

optimum level of cognitive engagement (Bench &

Lench, 2013;Westgate & Wilson, 2018). I wish to

propose a radically different source for the pain of

boredom, which though speculative, avoids the ad

hoc positing of human drives with no known

physiological basis. My novel proposal is that

much of the unpleasantness of boredom can be

explained by assuming that most people live with a

fairly constant level of nociception that is capable

of evoking mental pain under particular conditions.

Diffuse Nociception

When nociception is caused by, or appears to

be caused by, an intense bodily sensation, it is

experienced as physical pain, such that the sensory

and affective components are fused into a single

subjective experience that cannot be separated

phenomenologically. However, suppose that one is

receiving nociceptive signals that are so diffuse as to

be difﬁcult to localize subjectively in one’s body. In

that case, the nociception may activate the unpleas-

ant component of pain far more than any associated

sensory component. Therefore, this DN, although of

bodily origin, might nonetheless be experienced as

mental pain, which may then be falsely attributed to

psychological causes. There are several means by

which DN could occur, but a particularly common

source consists of the physiological changes

that follow the body’s stress reactions, often to

challenging psychological situations.

Possible Sources of DN

Reactions to stressful situations can have

considerable effects on several physiological

systems, and if these reactions occur often or are

sustained over time, the aftereffects can linger or

even lead to chronic physiological adaptations.

Such changes could evoke DN via some of the

mechanisms described next.

Cortisol

Stressful situations often lead quickly to the

activation of the sympathetic branch of the

autonomic nervous system as part of the “ﬁght

or ﬂight”response. In addition to the secretion of

adrenaline (i.e., epinephrine), the stress response

may eventually include the secretion of gluco-

corticoids, especially cortisol, through the activa-

tion of the hypothalamus–pituitary–adrenal axis.

Circulating cortisol is very helpful in emergency

situations because it increases the availability of

glucose for energy and curbs inﬂammatory and

immune responses until the emergency has been

resolved, at which point negative feedback loops

work to bring hypothalamus–pituitary–adrenal

activity down to normal levels.

Unfortunately, prolonged periods of stress can

lead to glucocorticoid resistance, thus defeating

the feedback loops and keeping the level of

cortisol high. High cortisol levels are particularly

toxic to hippocampal regions and reduce their

volume while increasing the volume of the

amygdala (Lupien et al., 2009). Because amyg-

dalar activity is associated with stress and fear

reactions, and the hippocampus plays a moderat-

ing role on amygdalar activity, the results of

chronic stress may produce hypervigilance and

overly labile affective reactions.

Inﬂammation

Normally, cortisol acts to reduce inﬂammation

in the body’s tissues, but a paradoxical conse-

quence of glucocorticoid resistance is that cortisol

loses its ability to stem inﬂammation, so that levels

of cortisol can be high simultaneously with

relatively high levels of proinﬂammatory cytokines

(Silverman & Sternberg, 2012). One likely candi-

date for the creation of DN is chronic, low-grade

6 COHEN

inﬂammation. In an extensive review article,

Slavich and Irwin (2014) made a convincing

case that stressful events lead to increased levels of

inﬂammation driven by proinﬂammatory cytokines

and that this systemic inﬂammation can, in turn,

produce all the common symptoms of depression.

It may be possible for one’s level of

inﬂammation to be too low to produce diagnos-

able depression and yet high enough to alter one’s

mood. This possibility was supported by the

results of Eisenberger et al. (2009), who injected

half their participants with an endotoxin in order

to elevate proinﬂammatory cytokines. Compared

to the placebo group, the endotoxin group

exhibited a signiﬁcant increase in self-reported

depressed mood 2 hr after the injection. Data

from an fMRI scan were collected at that time,

while the participants were subjected to social

exclusion during a computer game. During

social exclusion, the endotoxin participants who

had higher increases in one proinﬂammatory

cytokine (i.e., interleukin–6) also had greater

activity in their AI. In the females only, greater

interleukin–6 increases were also associated

with greater increases in activity in the dACC.

If inﬂammation can produce a depressed

mood, it follows that anti-inﬂammatory medica-

tions should be able to reduce depressive

symptoms, and in a systematic review and

meta-analysis, this is what Köhler et al. (2014)

found. However, it is important to bear in mind

that inﬂammation is only one of the conditions

that can lead to depression, so anti-inﬂammatory

medications may not be helpful for depressed

people who have little inﬂammation.

It is also important to note that inﬂammation

can increase pain sensitivity. In their review of the

hyperalgesia caused by inﬂammation, Watkins

and Maier (2000) suggested that increased pain

sensitivity is adaptive for healing, as it leads to

“sickness”behaviors that protect the body from

further damage. These authors discussed several

mechanisms to explain why peripheral inﬂam-

mation commonly leads to neuroinﬂammation

involving the brain and spinal cord. The resulting

vague malaise may be attributed and therefore

labeled in different ways depending on one’s

situation: for example, as loneliness, if one feels

deprived speciﬁcally of social interactions;

nostalgia, if yearning for “the good old days”;

boredom, if one feels certain that changing

activities will bring relief; or, perhaps, a general

feeling of dissatisfaction with one’s life.

Muscle Tension

Another likely source of DN is neural input

from chronically elevated levels of muscle

tension, which are especially prominent among

those diagnosed with generalized anxiety disor-

der. In their review of the association between

muscle tension and generalized anxiety disorder,

Pluess et al. (2009) suggested, among other

possibilities, that “… muscle tension may be a

way of coping with excess arousal caused by

anxiety”(p. 8). Goldstein (1965) recorded both

muscle tension as well as autonomic responses to

white noise in groups of psychiatric patients with

different diagnoses. She found the largest increase

in skeletal muscle tension in the depressed patients.

It is common to tense our muscles in antici-

pation of a predictable pain, such as an injection

(Kyle & McNeil, 2014), or a psychological

stressor, and this may be the simplest way we can

voluntarily create a slight amount of discomfort in

a controllable way to distract from the upsetting

stimulation we know is imminent. It is well

known that many people maintain considerable

levels of unnecessary muscle tension, which tend

to increase general arousal (Nielson et al., 1996),

as well as potentially making some people feel

generally uncomfortable.

Visceral Sources

The activation of the sympathetic nervous

system produces changes in blood ﬂow toward

skeletal muscles and away from visceral organs,

such as those of the gastrointestinal tract.

Gastrointestinal complaints are commonly asso-

ciated with anxiety disorders and may, at lower

levels, contribute to one’s level of DN.

How Common Is DN in the Human

Population?

This is a key question for my theory, because if

DN is to play a large role in producing a mental

experience as common as boredom, it must be

common as well. First, it is important to note that

there is widespread agreement that an experience

can only be labeled as boredom if it is unpleasant

and if the mental pain involved is fairly mild.

A moderate or severe experience of mental pain,

regardless of the situation in which it occurs,

would more likely be labeled as anxiety, depres-

sion, or, perhaps, existential boredom.

MENTAL PAIN AND DIFFUSE NOCICEPTION 7

Next, I suggest that even a very mild level of

DN can produce an overreaction in terms of

mental pain if negative emotions are evoked

because one feels trapped and resents being stuck

in a boring situation. Finally, symptoms of anxiety

and depression, including those that do not rise to

the level of a clinical diagnosis, are known to be

quite prevalent in developed countries, and these

symptoms are generally associated with physio-

logical changes, including increases in general

arousal, muscle tension, and visceral disturbances.

Thus, I propose that persistent mild physiological

disturbances are likely to be quite prevalent in

modern societies.

Unconscious and Preconscious Nociception

Depending on its intensity, nociception, whether

it is diffuse or localized, can be kept out of

awareness by distraction, and some nociception can

serve an important function without ever entering

conscious awareness.

Unconscious Nociception

Baliki and Apkarian (2015) contended that

much of nociception occurs without conscious

awareness and yet plays an important role in the

preservation of our bodily integrity:

The primary reason I ﬁdget in my chair while writing

this article is because nociceptors innervating my skin,

muscle, and bone command that my posture needs

adjustment. Whereas proprioceptors provide (conscious,

but usually habituated) information about the location

and position of my body in space, nociceptors provide

inputs that protect my body from injury. …As a result,

the nociceptive control of behavior routinely occurs in

the absence of consciously perceived pain, rendering it

“subconscious.”(p. 475)

However, note that later in their article, Baliki

and Apkarian refer to “unconscious nociception,”

so they appear to be using the terms subconscious

and unconscious interchangeably, which is not

unusual. Moreover, they are clearly not using

these terms in the psychoanalytic sense of

experiences that have been actively repressed.

Preconscious Nociception

Freud (1989) drew a useful distinction between

mental activity that is repressed and therefore

stuck in the unconscious as opposed to activity

that is not part of one’s awareness at the moment

but could easily become conscious; he referred to

the latter mental processes as being “preconscious.”

Dehaene et al. (2006) redeﬁned the preconscious in

more modern terms as “… a neural process that

potentially carries enough activation for conscious

access but is temporarily buffered in a nonconscious

store because of a lack of top-down attentional

ampliﬁcation (for example, owing to transient

occupancy of the central workspace system)”

(p. 207). A common example of sensory informa-

tion that moves readily from the conscious to the

preconscious is the sound of a motor that drones

steadily and is then noticed only when it stops. With

respect to bodily feelings, you can notice the feeling

of your clothing touching your skin or the feeling of

your body in contact with the chair you are sitting

on, but unless there is some discomfort or you are

askedtopayattentiontothose feelings, you will not

notice these preconscious sensations.

In fact, even somewhat uncomfortable bodily

feelings will fade into the preconscious if you are

sufﬁciently distracted and thus become precon-

scious nociception. Garcia-Larrea and Bastuji

(2018) pointed out that “… the combined activity

in the sensory-speciﬁc and second-order networks

is crucial to ensure the passage from pre-conscious

nociception to conscious pain”(p. 194). However,

as in the case of peripheral vision,it is reasonable to

suppose that some mental activity in the precon-

scious may be vaguely perceived and that some

preconscious activity may be close enough to the

border of consciousness to have someeffect on our

behavior as well as our feelings. Sensing that DN

is in the background could motivate people to

continue to engage in their preferred distractions.

I will return to the important role of distractions

shortly.

That Which Reduces Physical Pain Tends to

Reduce Psychological Pain

Pain-Relieving Substances

Any substance that has pain-reducing proper-

ties when entering the body will reduce DN as

Ihavedeﬁned it, and, if my theory is correct, it will

reduce boredom as well. Common experience

shows that people are rarely bored when under the

inﬂuence of alcohol, marijuana, opiates, or other

strong pain relievers, and that escape from boredom

is often cited as a reason for ingesting those

substances. Although I know of no research on the

8 COHEN

effects of pain relievers on boredom, there are

studies demonstrating the effects of several pain

relievers on other sources of mental pain. Given

that psychological pain is associated with cortical

activation that overlaps a good deal with the

activation produced by nociception, such results

should not be surprising.

Even a pain reliever as mild as acetaminophen

has been shown to reduce the psychological pain

of social rejection. In one ﬁeld study, half the

participants were randomly assigned to take two

daily doses of acetaminophen for 3 weeks, while

the other half took placebos (DeWall et al., 2010).

Social pain decreased signiﬁcantly over the

course of the 3 weeks for the acetaminophen

group but remained ﬂat for the placebo group.

That ﬁnding was conﬁrmed in a laboratory

setting, in which social rejection was produced

via a computer game, manipulated to make it

appear that the participant is being excluded by

the other, “virtual”players (Fung & Alden, 2017).

Participants randomly assigned to take acetamino-

phen rather than a placebo pill reported signiﬁ-

cantly less social pain. Using the same computer

game in a study of habitual marijuana users, more

frequent use was associated with greater feelings

of acceptance, following exclusion in the game

(Deckman et al., 2014).

The widespread use of alcoholic beverages in

our society for the relief of mental pain is

consistent with the fact that alcohol has pain-

reducing properties, which have been conﬁrmed

by experimental research (see Thompson et al.,

2017, for a review).

The Role of Distractions

In addition to substances that have a direct

effect on the nociceptive system, there are quite a

few types of distractions that can also relieve pain,

though the mechanism by which that occurs is

not always clear. One possible mechanism for

distraction follows from the “spotlight”metaphor

of consciousness. If the focus of attention is

inherently limited and further narrowed by a

reaction to nociception, then shifting one’s

attention to some engaging perception or activity

may displace the nociceptive sensations, moving

them from the conscious to the preconscious.

However, there is evidence that distracting

activities may have direct neural effects in terms

of the downregulation of nociceptive signals.

Even physical pain can be a distraction from

mental pain, as described next.

Controllable Physical Pain Can Be Preferred

to (Uncontrollable) Mental Pain

The results of one of the multiple studies

included in Wilson et al. (2014) gained a great

deal of attention in the popular press because in

that study some of the participants who were

simply asked to entertain themselves only by

thinking for 15 min, after being deprived of other

means of distraction, self-administered electric

shocks to themselves—shocks that they had

stated previously they would pay to avoid.

Because the Wilson et al.’s (2014) study has

received some criticism (e.g., Fox, Thompson,

et al., 2014), it is important to note that the self-

administered shock ﬁnding was soon after

replicated in at least two other independent

studies (Havermans et al., 2015;Nederkoorn

et al., 2016), which employed longer and more

monotonous (i.e., boring) conditions.

A more recent study by Yusoufzai et al. (2022)

found that a boredom-inducing condition resul-

ted in a greater frequency and intensity of self-

administered shocks as compared to a neutral

control condition, and that there was a signiﬁcant

correlation between the boredom proneness of the

participant and both the frequency and intensity

of those shocks. Of note is that these effects were

signiﬁcant when analyzed separately for partici-

pants who reported at least one past incident in

which they engaged in nonsuicidal self-injury

(NSSI), such as cutting themselves, but not when

analyzing only the participants with no NSSI

history. Overall, more than half of the partici-

pants self-administered at least one shock rated

as painful, which included some of the non-NSSI

participants. Surprisingly, although the study

made no attempt to recruit for NSSI, about 55%

of their sample fell into the NSSI category.

Given that the shocks in these studies were

under the control of the participants and that

controllable pain is less aversive than uncon-

trollable pain, it is reasonable to infer that at least

some of these participants were using controlla-

ble pain to distract from the uncontrolled pain of

their boredom. In terms of a possible neural

mechanism for this effect, Wiech et al. (2006)

found that the reduced aversiveness of control-

lable pain may result from downregulation of

MENTAL PAIN AND DIFFUSE NOCICEPTION 9

nociception originating in the anterolateral prefron-

tal cortex, a cortical area associated with cognitive

reappraisal of emotion.

Mind Wandering

The vast majority of people do not deliberately

inﬂict physical pain on themselves, and they do

not constantly experience mental pain. However,

in modern societies, it seems that most people do

engage almost continuously in distracting activi-

ties that may serve the function of keeping mental

pain from entering their awareness, or more

accurately, blocking nociceptive sensations that

would evoke mental pain were they allowed into

awareness. One line of evidence supporting this

assertion is the ubiquity of the subjective

phenomenon known as mind wandering, which

has been studied a great deal in recent years. Mind

wanderingiscommonlydeﬁned as mental content

that is independent of one’s environment and

external sensations, referred to more formally as

stimulus-independent thought, and is unrelated to

whatever task one is performing, in which case it is

labeled as task-unrelated thought (TUT).

Experience sampling studies have shown that

mind wandering is a common phenomenon for

most people; a recent review estimated that the

average person spends 30%–50% of their time

mind wandering (Kucyi et al., 2023). Therefore,

an article by Killingsworth and Gilbert (2010)

stirred up a good deal of controversy when they

claimed that mind wandering generally caused

people to be unhappy, concluding that “… ahuman

mind is a wandering mind, and a wandering mind is

an unhappy mind. The ability to think about what is

not happening is a cognitive achievement that

comes at an emotional cost”(p. 932).

The results of the “shock”studies discussed in

the previous section were essentially consistent

with the notion that people in general do not enjoy

thinking or just being alone with their thoughts.

However, to determine the causal connection

between mind wandering and negative affect,

Poerio et al. (2013) investigated their temporal

relationship and found that mind wandering was

not routinely followed by a negative mood, though

they did ﬁnd that a negative mood could evoke

mind wandering and that negative cognitions could

then exacerbate a negative mood. Analogous to the

self-administration of electric shocks when bored,

some people routinely dwell on negative thoughts

when mind wandering, which creates its own

mental pain. Although this may seem counterpro-

ductive and even masochistic, it is possible that

these individuals are shifting into a problem-

solving mode in a vain attempt to control their

mental pain. They may be trying to ﬁgure out the

origin of the pain in terms of past events and/or

planning ways to prevent its recurrence.

It seems paradoxical that regardless of whether

individuals enjoy thinking or ﬁnd it generally

unpleasant, it is well known that very few people

can voluntarily stop thinking completely for more

than a few seconds. The addictive quality of mind

wandering, whether in the form of pleasant

daydreaming or obsessive rumination, may be

explained by the consequences of the neural

activity that generates spontaneous thought, as

explained in the next section.

The Role of Neural Network Activity in

Reducing Mental Pain

The Default Mode Network

The neural activity that has been shown to be

largely responsible for mind wandering was ﬁrst

discovered when participants were asked merely

to rest in an MRI scanner while waiting for a task

to be given. The brain areas found to be most

active during these periods were referred to by

Raichle et al. (2001) as the DMN because it was

thought that these connected cortical areas become

active by default when no task or interesting

external stimulation is given. The main (hub)

regions of the DMN are generally considered to be

the posterior region of the cingulate cortex, along

with the adjacent precuneuscortex, and the ventro-

medial prefrontal cortex.

There are numerous studies demonstrating that

the DMN is activated when a participant is asked

to recall personal memories or make social

judgments (e.g., Andrews-Hanna et al., 2010;

Spreng et al., 2009). These results suggest that the

type of mental content that is most interesting, and

therefore most distracting, to the average human

waiting for a task in a boring environment consists

of autobiographical memories and thoughts con-

cerning social relationships. Given that the human

is a social animal, this could be expected.

Note that, as Raichle and Snyder (2007) found,

the DMN’s generation of spontaneous mind

wandering consumes a surprisingly large amount

of energy, even during rest periods in a scanner,

10 COHEN

so it is reasonable to suspect that there is a strong

motivation prodding its activity. I suggest that,

whereas the DMN originally evolved to serve

several important functions, such as keeping track

of one’s social relationships and status, as an

individual’s stress increases, the DMN has been

increasingly appropriated for the purpose of

reducing mental pain by generating the spontane-

ous, distracting thoughts known as mind wander-

ing. Moreover, brain-scanning research on DMN

activity suggests a direct neural pathway by which

DMN activity can reduce nociception.

Danckert and Isacescu (2017) recorded neural

activity in the AI as well as the DMN, while

participants watched a boring video and an engaging

one. Not only did they ﬁnd the expected increase in

DMN activity during the boring condition, but they

also observed downregulation of the AI (i.e., DMN

and AI activity were anticorrelated). The opposite

pattern was found during the interesting video:

DMN activity decreased, and AI activity increased,

relative to a resting condition. These results suggest

that DMN activity can reduce the pain of boredom

directly by inhibiting AI activity, which plays a

major role in the neural chain that produces the

aversive experience of pain (DMN activity would be

much less needed while watching an interesting

video). Note that a more nuanced study found that

not all tasks have the same inhibitory effect on the

DMN; Ulrich et al. (2016) reported that DMN

activity was signiﬁcantly more depressed during a

“ﬂow”condition (optimal task difﬁculty), compared

to both boring (too easy) and overloading (too hard)

task conditions. Thus, if one has a task to perform but

it is not very engaging, DMN activity may not be

sufﬁciently inhibited, allowing it to create TUTs.

Kucyi et al. (2013) found that participants who

tended to mind wander away from an experimen-

tally produced painful stimulus had stronger

structural (white matter) connections between the

DMN and the PAG of the midbrain, a major

processing area for nociceptive signals. Participants

exhibited greater functional connectivity between

those regions on the trials for which they reported

mind wandering, suggesting that the DMN was

capable of inhibiting nociception even in lower

brain areas. The pain-reducing consequences of

DMN activity may explain why this network is so

frequently found to be active during resting states in

an MRI scanner.

Note that any bodily function that can reduce

mental pain may be usurped for that purpose.

Ingesting food serves a vital biological function,

but it can also be overused in an effort to reduce

the mental pain of loneliness or mild depression,

for instance. DMN activity is particularly well-

suited as a pain reducer because it can be utilized

almost constantly, with apparently no build-up of

tolerance, and without dire physiological con-

sequences, though it does consume a good deal of

energy and can therefore be somewhat exhausting.

Cognitive Activity as a Pain Reducer

In many cases, mind wandering can reduce the

pain of boredom, but an engaging cognitive task,

which activates the central executive network,

can be even more effective against any type of

pain. Several studies have shown how cognitive

activity can directly inhibit nociception, in

addition to reducing activity in the DMN. For

example, Valet et al. (2004) scanned participants

receiving painful thermal stimulation (or only

warmth) while performing a demanding cognitive

(Stroop) task (or not). Subjective ratings of pain

unpleasantness were signiﬁcantly reduced during

cognitive distraction compared to no distraction.

This reduction in pain experience was accompanied

by overall reductions in the activity of various

cerebral pain processing regions and greater

connectivity between cingulofrontal cortical areas

and lower brain areas thought to play a role in

inhibiting physical pain signals (e.g., the PAG). The

authors concluded that their results supported the

notion that “… the prefrontal cortex exerts an

inhibitory control of sensory inputs to allow

cognitive networks to perform attention demanding

tasks”(p. 405). This reduction in pain could help to

explain the addiction of some individuals to video

games, puzzle solving, and other mentally effortful

hobbies. Perhaps, DMN or central executive

network activity can crowd nociception out of

the spotlight of awareness, but even if not, there is

evidence that activity in those networks can reduce

nociceptive signals heading for the cortex directly

by inhibiting neural activity in lower pain proces-

sing centers.

Pleasurable Sensations Can Reduce Mental

Pain

It hardly needs to be stated that mental pain can

be reduced by activation of the pleasure/reward

circuit in the brain. Very diverse forms of pleasure

(e.g., eating delicious food; listening to a favorite

MENTAL PAIN AND DIFFUSE NOCICEPTION 11

piece of music; meeting a loved one) have been

found to stimulate the same cerebral circuit,

which relies on the activation of the nucleus

accumbens and ventral palladium and reaches its

apex in a region of the orbitofrontal cortex

(Berridge & Kringelbach, 2013,2015). Given

that pleasurable feelings can drown out mild

feelings of pain, it is easy to understand why any

activity that activates the reward system, such as

eating (especially comfort food), sex, gambling,

or even shopping, can easily become psychologi-

cally addicting, to the extent that the activity in

question is successful in greatly reducing one’s

mental pain.

When All Distractions Fail

In the absence of successful distraction, DN

can shift from the preconscious to conscious

awareness, at which time it can trigger the cortical

activity that creates the aversive aspect of pain.

Being forced to perform tedious tasks or watch

monotonous videos for a lab experiment may

render mind wandering as the only available

distraction, and research shows that it is not a

strong enough distraction to prevent the feeling of

boredom for most people. However, even when in

daily life better distractions are available—for

example, a smartphone or tablet is handy—an

individual may react to the onset of boredom pain

with a negative emotion. For example, one is

stuck in trafﬁc or on a long checkout line, starts to

feel the pain, and gets upset or angry over being

trapped. The negative emotion may make it difﬁcult

to successfully engage in distraction so that the

boredom persists, as does the resentment over one’s

situation. If one is already experiencing a negative

emotion before getting stuck in a boring situation,

the pain of boredom would only exacerbate the

negative affect.

The Role of Mental Attitudes in Reducing

Pain

Our own interpretations of our bodily feelings

can play a major role in reducing or amplifying

the unpleasantness of our pain. For example, if

you had exercised vigorously the day before or

performed some manual labor and then woke up

feeling some muscle pains, these might well serve

as reminders of accomplishing a desired goal and

therefore may even be felt as somewhat pleasurable.

Wake up with the very same pains but no ready

explanation for them, and you may become alarmed

that you have the ﬂu or some other disease. These

concerns could lead to a greater focus on those

muscle sensations and even a neural facilitation of

the pain signals. Similarly, the heat of a sauna or the

sun on our skin can be pleasurable if it is a sensation

that we have been seeking, but not if it is being

imposed on us. These two opposing attitudes can be

referred to as sensory intake (acceptance) and

sensory rejection (Williams et al., 1975).

The Placebo Effect

Changing another person’s attitude toward

their bodily sensations can have a remarkably

large effect on the degree of pain they experience,

and this applies to mental, as well as physical,

pain. This change in attitude is surprisingly easy

to accomplish in most people via the placebo

effect. Even just the expectation of pain relief is

sufﬁcient to activate some of the brain’s pain-

reducing systems. Thus far, I have discussed the

way that neocortical activity can have an

inhibitory effect on the activity of nociceptive

processing areas in the lower regions of the brain.

However, there is a good deal of evidence that

reductions in pain perception due to changes in

expectations, such as occur with the placebo effect,

are at least partially mediated by the secretion of

endorphins (see Tracey, 2010, for a review).

Endorphins seem to play a major role in producing

the “runner’s high”that, for many people, is

generated by prolonged vigorous exercise. Much

of the evidence in favor of endorphins comes from

studies in which naloxone, which blocks opiate

receptors, was used to diminish, or even eliminate,

placebo effects.

The Effects of Mindfulness and Acceptance

Mindfulness-based stress reduction (Kabat-

Zinn, 2013) and acceptance and commitment

therapy (Hayes et al., 2006), both of which

incorporate mindfulness meditation techniques,

have helped to spur research on the use of

acceptance strategies for the reduction of physical

pain. A recent laboratory study (Haspert et al.,

2020) conﬁrmed the beneﬁts of acceptance

strategy instructions (e.g., “allow in any experi-

ence without further evaluation”) relative to a

control condition in which participants were

asked to just sense the thermal pain applied to

12 COHEN

their forearms without employing any strategy to

deal with it. These authors found that an attitude

of acceptance signiﬁcantly decreased both the

subjective intensity and unpleasantness of the

heat stimulation, relative to control trials.

Gard et al. (2012) scanned the brains of experi-

enced practitioners of mindfulness (Vipassana)

and control participants while they received

electric shocks under two conditions: attending

to the sensation mindfully or not (baseline).

Relative to baseline, the mindfulness practitioners

experienced signiﬁcantdecreasesinpainunpleas-

antness, while the controls did not. Their fMRI

results suggested that mindfulness does not use

executive control to mitigate pain but rather allows

one’s attention to focus on and fully process (i.e.,

accept) the potentially painful sensations. That is,

mindfulness produced pain modulation through a

mechanism different from that evoked by other

cognitive manipulations, including the use of

placebos.

A more direct comparison of the pain-reducing

mechanisms of mindfulness and placebo condi-

tions was conducted by Zeidan et al. (2015), who

scanned their participants’cortical activity during

painful thermal stimulation after they had com-

pleted 4 days of either mindfulness training or

practice using a placebo cream at the stimulation

site. Meditation produced a signiﬁcantly greater

reduction in pain intensity and, especially, unpleas-

antness than the placebo. Compared to the placebo

condition, meditation was associated with greater

activity in the orbitofrontal cortex and AI and

reduced activity in lower level pain processing areas

(thalamus and periaqueductal gray). In contrast to

meditation, the placebo condition was associated

with greater activity in the DMN and reduced

activity in the posterior insula and secondary

somatosensory cortex.

Zeidan et al. (2016) followed up their previous

study by using naloxone to block any placebo

effects mediated by endorphins. Participants trained

in mindfulness meditation were compared with a

book listening control group in terms of pain ratings

to thermal stimulation. Half of each group was

given a large intravenous dose of naloxone during

pain testing while the other half received an inactive

saline solution. Both meditation groups gave

signiﬁcantly lower ratings in pain intensity and

unpleasantness during meditation than at baseline;

in fact, there was virtually no difference between the

meditators given naloxone and those given saline.

For both control groups, there was actually a slight

increase in pain ratings. These results allowed the

authors to conclude that the pain reduction induced

by mindfulness, with its acceptance of the poten-

tially painful sensations, did not rely on the

secretion of endorphins.

The Effects of Increased Interoceptive

Awareness

There has been a great deal of research in recent

years on the topic of interoception. Carvalho and

Damasio (2021) described the interoceptive

nervous system as “… a large collection of

neural structures (some viscerosensory, some

somatosensory, some autonomic, some periph-

eral, some central) that cooperate to produce a

real-time map of the homeostatic state of the

body”(p. 2). Fischer et al. (2017) found that

training in a body-scan form of meditation

improved the accuracy of interoception, as mea-

sured by a heart-rate detection task. Wu et al. (2022)

also found that mindfulness training improved

interoceptive accuracy, as well as reducing negative

mood. Importantly, they found that the effect of

increased mindfulness on reduced negative mood

was fully mediated by the improvement in intero-

ceptive accuracy.

Acceptance of internal sensations involves

greater processing of the sensory dimension of

these stimuli, which can be expected to result in

more neural connections in the part of the brain

doing the processing; in the case of interoception,

that area is the insular cortex. In addition to the

changes in insular activity associated with

meditation, one of the most consistent ﬁndings

with respectto structural brain differences between

meditators and nonmeditators is the greater gray

matter concentration in the insular cortex of

meditators (e.g., Hölzel et al., 2008). In a review

article, Fox, Nijeboer, et al. (2014) pointed out

that: “… the studies reporting insula differences

involved practitioners with an intensive, explicit

focus on body awareness, including attention to

body posture, respiration, ambient tactile sensa-

tions, temperature sensations, etc.”(p. 61).

That an attitude of acceptance can reduce the

pain experience is consistent with the possibility

that the neural activity underlying the aversive

aspect of pain is based on a mobilization of the

brain’s resources to eliminate the source of the

seemingly threatening stimuli (i.e., sensory

rejection). Consequently, there is a narrowing

MENTAL PAIN AND DIFFUSE NOCICEPTION 13

of the ﬁeld of attention as activity relevant to

eliminating pain is prioritized, and this narrowed

focus may well enhance the unpleasantness of the

pain experience. That acceptance reduces mental,

as well as physical, pain is supported by a great

deal of meditation research demonstrating reduc-

tions in negative affect and improvements in

mood (see Sedlmeier et al., 2012, for a review).

Individual Differences in Boredom,

Neuroticism, and Interoceptive Accuracy

People vary a great deal with respect to how

easily they can become bored. This difference has

been quantiﬁed by several scales of boredom

proneness that have been developed in recent

years (e.g., Vodanovich & Watt, 2015). The wide

variation in boredom proneness found would

seem to be difﬁcult to explain in terms of the

strength of each person’s exploratory drive. One

would also have to explain why boredom proneness

is so highly correlated with neuroticism (e.g.,

Mercer-Lynn et al., 2013). First measured quantita-

tively by Eysenck (1983), neuroticism (sometimes

referred to as the opposite of emotional stability) is

considered to be an important personality trait

(McCrae, 1991). Moreover, boredom proneness

has been shown to be associated with various

psychopathologies (Sommers & Vodanovich,

2000), and Seiler et al. (2023) found even stronger

correlations between state boredom and measures

of mild psychopathology in mentally healthy

participants than they did using boredom proneness.

In addition to proposing that DN is a major

contributor to the mental pain of boredom, I would

also suggest that relatively high levels of DN

contribute to feelings of anxiety and depression

and thus add to one’s emotional instability. This

possibility could explain the high correlations

between measures of boredom and neuroticism.

If indeed DN plays a role in neuroticism, a

connection between interoceptive ability and self-

reports of anxiety and depression could be

expected. Critchley et al. (2004) tested 13 of their

participants with a heart-beat detection task and

asked them to ﬁll out standard anxiety and

depression surveys. They found that:

Across subjects, anxiety score correlated with intero-

ceptive accuracy during [fMRI] scanning. (…Pearson

R=0.64, P<0.05). Relative interoceptive accuracy

tended to correlate with depressive symptoms (R=0.48,

P=0.09) and trait ratings of negative affective

experience (R=0.51, P=0.08). (p. 190)

The Assumptions and Explanatory Power of

the DN Concept

The theory of mental pain and boredom I am

proposing rests on the admittedly speculative

assumption that the bodies of most people produce

some chronic level of DN, based on the various

physiological changes produced by past stressors.

I cannot prove that this is the case, but I have tried

to demonstrate that it is a plausible assumption.

The power of this theory arises from its ability to

explain a wide swath of common human experi-

ences, as well as a great deal of recent research, in a

parsimonious way, accounting for these phenom-

ena by means of well-known neural and hormonal

mechanisms. The main phenomena I have endeav-

ored to explain, at least partially, include the

following:

1. The ubiquitous and persistent occurrence

of mind wandering, and the difﬁculty most

people have when trying to stop thinking.

2. The current addiction to social media,

video and smartphone games, and other

easily accessible distractions.

3. The common presence of mild mental pain

when people are deprived of their usual

distractions.

4. Individual differences in boredom prone-

ness and neuroticism as a function of one’s

level of DN are moderated by one’s skill at

coping strategies and emotional regulation.

5. The stability of neuroticism as a trait and,

conversely, the stability referred to as the

“happiness setpoint”(Cummins et al., 2014).

Please note that I would not contend that the

theory I am proposing explains any of these

phenomena completely or even almost completely.

However, I do believe that the possible inﬂuence

DN has on human experience and behavior should

not be overlooked if we want to reach a full

understanding of these phenomena. What remains

to be explained is why the effects of stress are so

common in modern societies, and why there is

evidence of a growing level of feelings of stress,

anxiety, and depression, especially in young people.

Why Is DN so Prevalent in the Human

Population?

I mentioned earlier the ﬁndings that point to a

relationship between even low levels of chronic

14 COHEN

inﬂammation and feelings of sadness or depressed

mood. Unfortunately, this relationship has its roots

in the earliest stages of human development. In fact,

there is evidence that elevated stress hormones can

affect the fetus in utero. Although glucocorticoids

play a critical role in normal fetal development,

a high degree of maternal stress can lead to

abnormally high levels of cortisol and related stress

hormones in the fetal bloodstream, thus “repro-

gramming”the fetus’stress system to become

hyperactive, which predisposes the later child to

various affective and behavioral disorders, as well

as metabolic diseases (Harris & Seckl, 2011). In this

manner, heightened stress reactivity can be passed

from generation to generation epigenetically. These

predispositions can be exacerbated by poor mater-

nal care in infancy, especially if the mother is

suffering from depression. Moreover, stress hor-

mones can continue to enter the infant’s body

during breast feeding. Thus, it is possible to imagine

stress accumulating over the generations.

There is a good deal of research demonstrating

that early life stress (e.g., extreme poverty, abuse,

or neglect) has long-range behavioral effects on

later childhood and adolescence, as well as higher

lifetime rates of depression (e.g., Evans &

English, 2002;Slavich & Irwin, 2014). Human

infants, compared to our primate cousins, are in a

totally helpless and dependent state for an

unusually long period of time. During the ﬁrst

few months of life and even the ﬁrst year or so,

babies need an enormous amount of attention to

avoid stress reactions from not getting their needs

met in a timely fashion, and even the best parental

efforts will undoubtedly fall short of the womb-

like environment infants still need.

Anthropologists have noted that a “full-term”

human infant is born as much as a year prematurely,

especially when compared to our primate cousins

(Gould, 1977). Although there are certainly

evolutionary advantages to having a large, deeply

convoluted brain, it remains to be seen whether our

intellectual advantages will outweigh the disad-

vantages of early stress that programs our neural

and hormonal systems to deal inefﬁciently with

later stressors.

Proposed Experimental Tests of the Theory

A number of testable hypotheses can be derived

from the theory of boredom that I am proposing,

some of which parallel research cited in this article.

For example, just as an inﬂammation-producing

drug has been shown to increase a depressed

mood, the same type of drug can be expected to

increase the boredom induced by a monotonous

experimental task or video, as well as increasing

mind wandering (i.e., TUTs) and DMN activity

during the task. Any drug or manipulation that can

produce a noticeable amount of DN should have

the effect of increasing the likelihood of boredom

during a monotonous task and increasing the

unpleasantness of any boredom that occurs.

Other possible ways to produce DN in the

laboratory may include raising the room temper-

ature just enough to be a bit uncomfortable,

having the participant wear somewhat uncom-

fortable clothing or assume a slightly uncomfort-

able sitting position. The key to a successful DN

manipulation would be to titrate the conditions

such that the participant is not able to localize the

discomfort or attribute it to the environment.

Conversely, just as a mild pain reliever (i.e.,

acetaminophen) has been shown to reduce the

unpleasant feeling of social exclusion, a pain-

relieving drug, as compared to a placebo, can

be expected to reduce the unpleasantness of an

experimental boredom induction. An anti-

inﬂammatory drug, shown to reduce depression

in some individuals, may have a similar effect.

Alternatively, training in a body-scan meditation

that includes the cultivation of nonjudgmental

attention to, and acceptance of, even uncomfortable

bodily sensations, prior to a boredom induction,

should reduce self-reports of state boredom.

Training in progressive muscle relaxation, by

reducing excess muscle tension, could have

essentially the same ameliorating effect. In a two-

factor boredom induction experiment, one could

cross a DN manipulation with a pain-relieving drug

to test the effects of both independent variables and

their possible interaction.

Summary and Conclusions

In this article, I have attempted to present a

plausible and parsimonious theory to account for

most of the mild mental pain that most humans

seem to experience during boredom. The theory

rests on the assumption that the bodies of most

people, at least in modern societies, generate a

fairly constant level of DN that is intense enough

to evoke a mild degree of mental pain when it

enters conscious awareness. This level varies

from person to person, depending on their history

of stressful events (in terms of the intensity,

MENTAL PAIN AND DIFFUSE NOCICEPTION 15

frequency, and duration of those events), as well

as various personality and physiological factors

that affect the individual’s resilience. The level of

DN is low enough in most people to be kept in the

preconscious almost continuously by the use of

coping strategies, often learned early in life, such

as engaging in successful distractions, including

thinking in the form of inner speech. However,

higher levels of DN are related to higher degrees

of boredom proneness and neuroticism. Negative

emotions can increase DN, and the pain evoked

by DN can evoke negative emotions or exacer-

bate ongoing ones.

In general, I view DN as a potential ampliﬁer of

normal human drives, to the extent that satisfying

those drives can keep DN in the preconscious.

Thus, as examples, the ampliﬁed hunger drive

becomes stress (over)eating; the ampliﬁed drive

toward social interaction can lead to overindul-

gence in social media; and the ampliﬁed explor-

atory drive can lead to extreme sensation seeking.

On an optimistic note, the research I have described

on the beneﬁts of an attitude of acceptance toward

all of one’s bodily and mental feelings suggests the

possibility that training one’s introspective ability

can reduce negative reactions to nociception and

may ultimately break the vicious cycle that

maintains one’s chronic level of DN.

Finally, it has been well established that various

regular meditative practices increase the trait of

mindfulness (e.g., Kiken et al., 2015), which in

turn is negatively related to boredom proneness

and neuroticism. Regular practice of these

methods holds the promise of helping us to raise

our happiness setpoint and lower our neuroticism.

Ironically, the boredom most people feel whenﬁrst

sitting to meditate tends to steer them away from

a practice that could reduce their proneness

to boredom (Osin & Turilina, 2022). A fuller

understanding of why mindfulness practices may

produce beneﬁts in the long-term may help to

encourage this practice.

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