Reinterpreting the Einstein-Bergson Debate through Contemporary Neuroscience

We aim to recast the famous debate between Albert Einstein and Henri Bergson in 1922 in the context of contemporary psychology and neuroscience as informed by phenomenological analysis. We show that their disagreement is not as deep as has been considered previously, including Einstein and Bergson themselves. We argue that Bergson ’ s dynamic view of consciousness as time constituting complements embodied models of time consciousness in modern neurophenomenological approaches. The phenomenological unity of time and self, including its inherent dynamism, is similar to that of recent neurophysiological con-ceptualizations, which suggest that the constantly ongoing integration of somatic signals over time generates a floating experience of the emotional self across moments of self-awareness. Embodied concepts of consciousness are thus grounded in the dynamic processes constituting the living body. We high-light empirical evidence informed by recent neurophysiological studies showing that the experience of time and the explicit judgment of duration are governed by emotional and visceral processes which share a common underlying neural processing system, the interoceptive system. Especially the insular cortex has shown to be related to the judgment of time as dependent on bodily and emotional states.

gained the upper hand among boththe scientificcommunity and the public. To this day, the debate is considered as ac lash between two toweringf igures with radicallyopposite views, and manyw ould consider Bergson'sp erspective as either confusedo rn ot reallyi nl ine with science.
Even at the time of their initial debate on April 6, 1922, and in spite of Bergson'sreputation as one of the greatest philosophersatthattime,² Bergson faced harsh criticism as aconfused and irrational thinker.³ Thispolarization of the debate quicklytook it into dramatic proportions.Rationality and scientific methodologywas associated with Einstein by his supporters,who thought of Bergson as acult figurewho promoted mystical approachestothe crucial topic of the nature of time. But Bergson'ss upporters thought of his criticism as an enormouslyi mportant attack on areductive and mechanistic perspective thatdeprivedour view of the world of its naturalvitality,turning it into aworld of frozen relations-in the case of time, "afrozen grid that scientists call spacetime" (Montemayor2013, xi), also known as the "block-universe".
Einstein famouslyt ook the passageo ft ime to be as tubborn illusion. Bergson, by contrast,c onsidered time as the foundation of vitality,o ri mpulses, as well as of all dynamic and meaningful relations,including the sensorial properties we are conscious of. Is their debate, thus portrayed, between av iew that presents reality as as et of frozen relations versus av iew that reduces objective temporalp roperties to impulses and vital forces?Adebate between the mechanistic agenda of scientific superiority and av iew of the world based on the human spirit?O nt his superficial readingo ft he debate manyd istinctions would disappear from view;w ew ould miss important nuances of how Einstein and Bergson clarified their views in interactions with other thinkers. In particular,wew ould ignore Bergson'sc onstant interest in mathematics and physics as well as Einstein'si nterest in the question of what could explain the illusion of time.
Although thereissome truth to the claim that this debate is astark illustration of "aworld largely split into science and the rest" (Canales 2015,7), we believec ontemporary neurosciencea nd current psychological approaches to phenomenologyhavemuch to offer to the project of recasting and reinterpreting this debate in new and insightful ways.I ti sn ot our purpose to settle the debate or claim ad efinitive interpretation of it.Our main claim is that if one understands Bergson as ap henomenologist with specific claims about the psychologyo f time, then the alleged chasm between Einstein's scientific side and Bergson's un- See Dewey (1912).  See Berlin (1935); Russell (1912). scientific and irrational sides tarts to close and vanish. IsaiahB erlin givesu sa clue as to how we can approach Bergson'sp erspective in his criticism of Bergson'sw ork. Jimena Canales writes: "The historian and theorist Isaiah Berlin associated him [Bergson] with the 'abandonment of rigorous critical standards and the substitution in their place of casual emotional responses'" (Canales 2015,13).
Surely, there is ap lace for the role emotion and consciousness playi no ur lives, and there are certainlys cientific approachest ot ime consciousness.B ergson is not typicallyc onsidered ap henomenologist,al ineaget hat is associated with Edmund Husserla nd his students, who actuallyd istanced themselves from Bergson (Canales 2015,1 39 -152). We brieflye xplore this issue in section 3, but it is important to appreciatet hat Bergson'se mphasis on time as experienced through the vitality of emotions, motivations,a nd conscious awareness is ac entral topic of contemporary neuroscience.⁴ The main point of this discussion is to show that,g iven the current evidence on the issues Bergson'sp hilosophyrevolvedaround, his seemingly titanic disagreement with Einstein might be based on an unfortunate misunderstanding,g iven the contemporary perspectiveso nt ime in metaphysics and psychology. On the one hand,E instein is right in insistingo nt he mind-independent character of temporalr elations,a s the next section shows. On the other hand,B ergson is also right in insisting on the importance of experienced time as essentialtoour understanding of ourselves, as section 3s hows. These are both plausible and even complementary perspectiveso nt ime. As mentioned, the keyt oa ppreciate how they might be complementary is to understand this debate in the light of contemporary neuroscientifica pproaches to the psychologya nd phenomenologyo ft ime. In other words, science has changed dramaticallyi nt he fields of cognitive psychology and neuroscience, providinge mpirical evidence thatE instein and Bergson did not have available. Recastingt he debate between Einstein and Bergson under the light of contemporary psychologys hows that their disagreement is not as deep as has been interpreted so far,a nd certainlyn ot as deep as bothE instein and Bergson took it to be.

2M etaphysical Implicationso ft he Einstein-Bergson Debate
In what sense was Einstein right when he said that "the time of the philosophers did not exist" (Canales 2015,5;Il n'yadonc pas un temps des philosophes). Dur-ing the event in which Einstein met Bergson, Einstein clarifiedwhat he meant by this. Canales reports: "What Einstein said next that evening was even more controversial: 'There remains onlyapsychological time that differs from the physicist's. At that very moment,E instein laid down the gauntlet by consideringa s valid onlyt wo ways of understanding time: physical and psychological" (Canales 2015,5 ). What kind of challengei st his?C an there reallyb eathird time, besides the physical and the psychological? Canales describes Bergson'sresponse to this challengeasfollows: "The simple, dualistic perspective on time advocated by Einstein appalled Bergson. The philosopher responded by writing aw hole book dedicated to confronting Einstein. His theory is "ametaphysicsgrafted upon science,itisnot science" (Bergson 1999,47). The book in question, Duration and Simultaneity,laysout aconception of time that identifies time with the continuity of our inner life, not as a stagew ith subsequent and discrete parts or transitional snapshots,b ut as a vital flow thatdetermines duration itself,i nopposition to everythingt hat is rigidlya nd metricallyd etermined. Kant famouslya lso identifiedt ime with the "inner sense" of our minds, and said that it is in this inner intuition that we arrive at our knowledge of arithmetic -as opposed to geometry,which is based on our intuition of space or "outer sense".I nterestingly,B ergson believes this is a recapitulationo ft he scientific perspective Newton favored in terms of absolute time and space (Kant'sp urpose is to defend the Newtonian system). Thus, perhaps the best waytocharacterize Bergson'saccount of time as the vitallycreative forceo fd uration in "our lives" is to define it as an on-metric experience,o ra conscious experience that cannot be reduced to anym etric relation, such as simultaneity,t emporalo rder,o r" clock-based" duration.A sd iscussed further below,t his is an approach the phenomenological movement, notablyE dmund Husserl, favored and elaborated on.
But surelym etric relations matter to how our perception and experience of time are structured. Bergson and Einstein could not know all the details at the time of their debate, but cognitive scientists now have provided ample evidence showing that the circadian clock and ashort "stop-watch" clock are very important to how we perceive time.B oth clocks are "psychological" in Einstein's sense, because they help us represent environmental relations in terms of the temporalproperties of events (see Montemayor2013,for aphilosophical account of how these clocks generate representations that ground justified beliefs about time). This is psychological time, but it fundamentallydepends on the activity of clocks: neurallyi nstantiated time-keepers.S om etric relations matter,a nd must be somehow reconciled with the vital duration we experience with emotions.
What about the phenomenologyo ft ime, or what Bergson describes as the transcendental nature of the flow and unity of our experiences? It mayb e more productive to think of it,not as athird kind of time, what Einstein calls "the time of the philosophers".Instead, reflections about the phenomenologyoftime should be informed by our knowledge concerning physical and psychological time. The phenomenologyoftime cannot be completelyindependent from physical and psychological time and in that sense, adualistic account is foundational in order to understand the flow of time. But also,the situation is not fullyreductive -the non-metric character of the flow and phenomenologyoftime needsto be explained.E veni fE instein is right and the flow of time is illusory,wem ust explain what produces such an illusion.
Adual model of time perception explains some of the key features addressed by both Einstein and Bergson. Brief scales of time in the millisecond rangea re directlyl inked to temporalf eatures of the environment but at the seconds' stage, the phenomenologyofpresencestarts weaving all the contents of our conscious awarenessinaunity thattranscends the previous metric structures (Montemayora nd Wittmann 2014). The experiential and visceral vitality of our emotions and agency,w hich are the central focus of Bergson'sa ccount of time, can be explainedi nt erms of ad ual model that distinguish agency from early sensorial temporalp rocessing (Montemayor2 017a), unconscious processing from visceral and arousal-related temporal awareness (Montemayor2 017b) and with respect to the present,aphenomenal present from as ensorial present (Montemayor2 013). Earlys ensorial processing concerning the relations of time order and simultaneity mayo ccur without conscious awareness at the first stageo fp rocessing (a pre-agential processing). Then the agent is equipped with the necessary representational framework for integrating arousal-related informationwith her overall conscious experience in the phenomenal present (distinct from the sensorial present thatr elates stimuli in terms of simultaneity). Thus, Bergson'sa ccount of time based on emotions and agency is compatible with the perception of metric properties,associatedwith time in physics (involving the relations of simultaneity,t emporalo rder,a nd duration).
So, what exactlyare the metaphysical implications of Einstein'schallengeto Bergson?O ne can accept Einstein'sc haracterization of ad ualistica pproach to time, as well as most of what he said about physical time in opposition to Bergson, partlybasedonthe psychological findingsand proposals just mentioned. In addition,aswillbeexplained in the next section, one can still justify the importance of the phenomenological project formulated by Bergson. Theseare not antagonistic or irreconcilable tasks. From an epistemic point of view,o ur beliefs about temporal relation need to be justified and for this we need the environmentally-based metric relations of simultaneity,d uration, and time order.
Bergson'sc haracterization of Einstein'sv iew as "metaphysicsg rafted upon science" cannot be right without some clarification. As Reichenbach (1958) ex-plains, it is because of Einstein'st heory of Relativity that we have arriveda ta n empiricallytestable theory of time and spacethat is alsosusceptible of rigorous mathematical formalization, unlike all the preceding views on time and space which depended on axiomatic first principles and ap riori intuitions. Thisi sa complex issue⁵ and we will examine this claim from ap henomenological perspective in the next section. But the main point is that Einstein'sc ontribution to the study of space and time was deeply philosophical. Reichenbach (1958) argues extensively for the case that Einstein transformed the epistemology of space and time by updating it with ideas thatare equallyapplicable the psychological space and time as well as physical spacetime. Reichenbach shows that coordinative definitions are essential for the empirical, rather than strictly apriori, study of space and time and that these coordinative principles must be in place any time one asks the questions concerning what is the actual geometry of as pace and time givenc onventions about rigid bodies -again, includingp sychological space and time (e. g.,visual, auditory,p roprioceptive). Bergson'sg eneral statement thatEinstein'stheory is "metaphysics grafted upon science" misses entirely this point.
If Einstein is right,and there are onlyphysical and psychological time, what follows for the metaphysics of time? As mentioned, one immediate implication is the approach to this issue, shifting from exclusively apriori or armchair perspectivestoaposteriori or empirical ones (Reichenbach takes this to be the most important contribution of Einstein, particularlya gainst Kant). We offer in the concludings ections evidence for bothp sychological time and the phenomenology of time, as the latter functions as the informative basis of the former,thus confirming this implication. Crucially, all of the contemporary metaphysical views of time are attempts at addressingE instein'st heory.While Einstein seems to have favored ab lock view of the universe in which changeo rp assageo ft ime have no place and the present is not unique, manyr ecent views of time modify the strict requirementso ft he block universe to accommodate either changeo rp assage.⁶ Fori nstance,s cientific theories of statict ime similar to the block universe explain our experience of the passageo ft ime by appealing to neuroscience,⁷ or by proposingt hat while events might be objectively static, changed oes occur in terms of temporalorder in relation to the emergent macroscopic properties thatw ea ssociate with psychological time.⁸ So-called "GrowingB lock" the- See Ryckman (2005).  See contributions in Dolev and Roubach (2016).  See Barbour (1997).  See Rovelli (2018a); (2018b). ories appeal to real becoming,⁹ in away that depends on am oment that can be characterized as the "now" involved in the passageoftime.¹⁰ Arguably, anytheory thatappeals to amoment in which time branches, or in which there is aspotlight thatdemarcates the GrowingBlockofspacetime is presumablyaview that depends on ak ind of objective characterization of the present moment as uniquelyr elevant for demarcating the boundary between the real and the possible.¹¹ However,thereare convincing arguments showing that passagecan be accommodated in ablock universe view,without making our experience of passage fundamental or primitive.¹² These are all metaphysical and scientific views of time that try to accommodate the kind of passaget hat seems to have been, at least partly, the focus of Bergson'st heory of time.C ontemporary versions of the Atheory dispense with such arobust understanding of passage, for instance by emphasizing instead property instantiation.¹³ While there are intricate issues concerning the topology,metric, and other metaphysical aspects of time that are relevant for the precise formulation of the Aand Btheories, our focus here is on how Einstein and Bergson understood the physicsoftime in relation to psychology.
Bergson'sc hargea gainst Einstein'st heory,n amelyt hati ti nadequatelyi njects metaphysics into physics,h as not aged well. Most contemporary philosophers and scientists find various philosophical insights in Einstein'st heory,i ncludingu nprecedented epistemological insights about the nature of spacetime. But the relation between the psychological and the phenomenological remains acrucial difficulty.Einstein might be right that there is no "third time" of the philosophers, but surelysimplysaying that there is psychological and physical time is not enough. The "stubborn illusion" of time frames our life very deeply, as Bergson described, and  gist,B ergson presents as erieso fe pistemic points thatE instein should have taken more seriously.I np articular, Bergson'sc haracterization of time as irreducible to discreteq uantities or mechanicalc haracterizations is one that plays a very important role in the reception of Einstein'stheory within the physics community.Thesea re issues concerning the conscious basis of metric relations, coordinates ystems and mathematics itself. Experienced duration is av ital unity from which all these abstract characterizations of time emerge.This section illustratesh ow Bergson is not alone in making these points, and in fact,h ei si ni llustrious scientific company. The concluding sections show how contemporary approachest on eurosciencea nd phenomenologycan be used to update and reinterpret the Einstein and Bergson debate. Hermann Weyl explicitlyaddressed the problem of "how to bridge the gapor 'chasm' between the intuitivec ontinua of space and time and the mathematical continuum. Based on the work of Edmund Husserl, Weyl opted for phenomenal time as the sourceofour intuitions of the mathematical continuum" (Montemayor 2012,5 6).B ergson'se mphasis on the vital and life-dependent character of phenomenal time are even more in line with current scientific evidence, as the research on interoception discussed below demonstrates.B ut there is much in common between the Husserlian approach and Bergson'sh ere. One can find some of the samethemes, and criticism to the mechanicalview of reality initiated by Husserland later by Heideggerinthe work of Bergson. In adiscussion on the idea of duration contained in Time and Free Will (1889/1913), Bergson proposes thatc onsciousness presents the sequencea nd homogeneity of numbers in atwo-fold manner,asadiscretesuccession for cognition and as an underlying unit,the unit of conscious awareness.Inthe unit of phenomenal time, nothing is discretea nd succession is replaced by seamless continuity.There is av ery fundamental epistemic point about physics in these remarks,i ncludingt he work of Einstein, as Weyl famouslya rgued in various scientific works: The epistemological thesis that cognition in the exact naturalsciences is the joint ('relative')p roduct of objective characterization in precise mathematical concepts, and the subjective 'immediate life of intuition',b elongst ot ranscendental-phenomenological idealism.I ni ts terms,t he very sense of objectivity is constituted within 'transcendental subjectivity',a nd accordingly, there must indeed be avestigew ithin the 'objective world' represented by the mathematical/ conceptual theories of physics of its 'origin' in the 'absolute' beingofthe given-to consciousness.Through reflection on the applications of mathematics in physics, Weyl recognizeda ni neliminable trace of the subjective sourceo fa ll objectivity in the arbitrary fixing of al ocal coordinate system (Ryckman 2005,135).
The immediate life of intuition is grounded, accordingt oB ergson, in the very vitality of emotion and creative feeling.I nt ime, this insight became ac ru-cial assumption of the view called "the Embodied Theory" of the mind. Ideas about embodiment alsoe ntered the debate surroundingh ow to best approach the phenomenological project originatedb yH usserl. Merleau-Ponty,i np articular,e xplored the bodily-based forms of spatialitya nd temporality thatw erei nfused with expectation, emotion, and creativity,just the wayBergson envisioned (more on this below,p articularlyw ith respect to findingso ni nteroception). On this Bergsonian account of the phenomenologyoftime, our experience of vitality in time, in our lives, is as ourcen ot onlyofc reativity and visceral engagement, but also of attentive strategies towards formalizations that depend on the source of the flow of life-time for theirc ontent,s uch as numerical and geometric abstractions.
Thus, Einstein is partlyr ight whenh ea ffirms therea re onlyt wo times, psychological and physical. This does not mean, however,t hat he should have ignored Bergson'sc laims about the centrality of phenomenology. Weyl,who was as qualified aphysicist as was Einstein, fullyappreciatedthe importance of phenomenology, and he gave it,accordingly,acritical role in his scientific and philosophical writings. As Ryckman explains in the passageabove,Weyl sees the inescapable appeal to coordinate systems as depending fundamentallyo no ur subjective awareness of time. This obviouslyincludes the kind of objective coordinative definition emphasized by Reichenbach in his work on Einstein.
Bergson, as aphenomenologist,can be vindicated in the tribunalofhistory. His role in his debate with Einstein wasi mportant for philosophical and scientific reasons,rather than ideological and mysticalmotives. But,tor estate differentlyt he previous point,what would it mean to sayt hatt he "time of our lives" associated with morality,free will and creativity is "not-psychological" and, even more puzzling,what would it mean for the time of our livestobeabsolutely unrelated to metric relations,s uch as simultaneity and time order?T he following sections address these two issues, first by giving an account of the perception of temporalr elations and second, by providinge vidence of the psychological and neural basiso ft he experience of time.
Bergson is right that the irreducible datum of time is the flow and passageof our inner lives, which manifests itself at its clearest in the visceral and empathic reactions we associate with the vitality of conscious awareness (see Montemayor and Haladjian 2015,for how these reactions are best understood as phenomenal consciousness,d issociated from the more strictlye pistemic functions of attention). But this is not the whole story.T his continuous flow is also the basis upon which more hypostatic forms of attention depend, particularlyconcerning mathematical objects. The foundation of coordinative systems for mathematics, physics,a nd science in general, can be found in this "immediate life of intuition".
But what do these phenomenological observations have to do with what Einstein called "psychological time"?A se xplained above, with respect to the philosophyo fs pace and time, Einstein'se pistemological contribution wast o movet he debate from as trictlyapriori analysis (judgments arriveda tt hrough reasoninga nd intuition alone)t oap osteriori reasoning (judgments arriveda t on the basis of empirical evidence). Perhaps asimilar advancement maybenecessary in the caseofp henomenologyand psychologyoft ime. The next sections provide evidence that is relevant for this project; these are scientificfindingsthat neither Einstein nor Bergson had available. Section 4d iscusses evidence concerningt he perceptual capacities underlying representations and inferences about metric structure, or the environmental properties of events that must be understood in terms of relations of simultaneity,d uration,a nd temporalo rder. Section 5d iscusses findingso nt he relevanceo fi nteroception for what Bergson called "livedt ime".

4C urrent State of Affairsi nt he Psychologya nd Neuroscienceo fT ime Perception
The systematic studyo ft ime perception became possiblei nt he second half of the 20 th century with the advent and elaboration of internal-clock, or stopwatch, models developed in the cognitive sciences.¹⁴ In essence, these models posit that apacemaker sends out pulses which are sent to and stored in an accumulator by passing through agate.¹⁵ Accordingtothese models the number of pulsesstored in workingm emoryw ould represent experiencedd uration. Stronge vidence for clock-likep roperties of this timing system, i. e., as countingo fc lock ticks, comes from empirical work showingh ow physiologicalm anipulation of the assumed clock rate induces relative under-and overestimation in animals and humans (respective right-o rl eftward shifts in the psychometric response function).¹⁶ To more accurately account for human timing performance in af urther developmental step, an element was added to the model pertaining to the attentional focus of ahuman observer.Accordingtothe attentional-gatemodel¹⁷ pulses are onlyr egistered when attention is directed to the passageo ft ime and a  See Wearden (2016).  See Treisman (1963); (2011).  See Meck and Church (1983); Meck (1996).  See AGM; Zakaya nd Block (1997). switch is closed which in turn opensagatetothe accumulator.This means that the estimation of duration is always adual task.Anobserver can divide attention between experienced time and non-temporal features of an event.D uring ap eriod of waitingf or ap ersonally important event to occur (the phone call of a loved person) most of our attention is directed to the passing of time, which then leads to an overestimation of waiting time.¹⁸ Accordingtothe AGM, two factors modulatet he estimation of duration:¹⁹ (1) An increased emotional (bodily) arousal level increases the pacemaker rate and in turn leadst or elative greater accumulation of pulses duringag iven time span; (2)Astronger focus of attention to time similarlyl eadst om ore inflow of pulses in the accumulator as the postulated gate is more frequentlyo pen. Importantly, the AGMr elates onlyt o time judgments under prospective conditions in which subjects are explicitlyinstructed to attend to time.Under retrospective conditions, in contrast,studyparticipants are unaware thatt hey will later be asked to estimate time while they perceive an event.T he task becomes retrospective when the participant is instructed to judge duration after the event has ended. Then memory load pertaining to thatp eriod of time defines subjective duration; the morer ecall of changing features of the past interval, the longer duration estimates.²⁰ The AGMi su sed in purelybehavioural studies to explain relative over-a nd underestimations in prospective time perception tasks in an intuitively plausible way. Forexample, concurrent secondary tasks lead to arelative underestimation of duration because attention is diverted from the primary timing task; with increasingwork load of the secondary task an increasingunderestimation of duration is detectable.²¹ In one study, less attractive faces wereassociated with arelative underestimation of duration as compared to neutral and attractive faces.²² This was interpreted as stemmingf rom the dislike and therefore reduceda ttention to the unattractive stimuli. Regarding the factor of arousal, judging duration of emotional negative stimuli with presentation times around 2seconds as compared to neutral stimuli in one study not onlyled to relatively greater physiological arousal (as measured with the skin conductance response) but the negative soundsa lso generated relatively longer subjective duration.²³ Usingv ideo clips with presentation times between 16 and 40 seconds,s low-motions cenes,a s compared to real-time scenes,i nduced lower arousal (lower respiration rate  See Jokic et al. (2018).  See Burle and Casini (2001); Droit,Volet and Meck (2007).  See Brown (1985); Zakaya nd Block (1997).  See Brown (1985).  See Ogden (2013).  See Mella et al. (2011).

Reinterpreting the Einstein-Bergson Debate
and smaller pupillary diameter)w hich in turn was associated with as ystematic underestimation of duration.²⁴ Although practicallys peaking empirical results do not always conform to the model'spredictions,²⁵ the AGMispopular because of its strong heuristic value in explaining everydaysubjective time. In the case of experiencedb oredom, the focus of attention is predominantlyo nt ime, and duration expands.²⁶ During entertainingactivities, when one is absorbed in what is happeningw ed on ot attend to time and the event passes comparablyq uickly, time flies.²⁷ Regarding the neural basis of subjective time, i. e., the question of how and where in the brain time in the rangebetween milliseconds and multiple seconds is processed,f or manyd ecades research focused on several distinct neural systems.Researchers are informed about the implication of certain neural networks involved in duration judgment using neuroimaging techniques (fMRI, EEG), through neuropsychological testingofbrain-injured patients, by the transient interruption of neural processes with transcranial magnetic stimulation( TMS), and by assessing the effects of psychopharmacologicala gents.F or several decades two competingm odels weref avored for explaining the neural basis for sensorya nd motor timing:( 1) Fronto-striatal circuits comprisingr ecurrent loops between frontal cortex (SMA), caudate-putamen, pallidum and thalamus, which are modulated by the dopamine system;²⁸ (2)t he cerebellum, which has non-overlappingn eural modules with different neural delayp roperties which could encode duration.²⁹ Empirical evidence also pointstoseveral other regions such as the right posterior parietal cortex, which might be involved in general magnitude processing of time,s pace, and number,³⁰ and the insula, the interoceptive cortex, i. e., the primary cortical area for receiving bodilys ignals.³¹ Meta-analyses of functional neuroimaging studies shed light on the duration dependency of the neural correlates of time. It seems that although the identified brain areas are involved in both the processing of sub-a nd supra-second intervals,r elative more activation of subcortical structures appears with sub-second stimuli, whereas relative more activation of cortical regions is detected with supra-second stimuli.³² Such aduration-dependent distinctionhas also been detected for effects of manipulation on the serotonin and dopamine transmitter systems. Fore xample, healthyp articipants in timing studies wereg enotyped to comparei ndividual temporalp rocessing performance with genetic polymorphisms. Whereas temporal discrimination variability of visual stimuli around 500 ms werea ssociated with ap olymorphism related to D2 receptor density in the striatum, timing variability with stimuli around 2swas associated with a polymorphism related to synaptic dopaminergic metabolism in the prefrontal cortex.³³ This duration-dependent distinction between striatum and prefrontal cortex fitsw ith the abovem entioned sub-a nd supra-second activation for subcortical and cortical brain regions,respectively.³⁴ Gene polymorphismsrelatedto the serotonin system, but not the dopamine system, werea ssociated with duration discrimination of longer intervals, namely with several seconds duration (with an averageo f4 .8 s).³⁵ This conforms to behaviouralf indingso fd oubleblind, placebo-controlled, studies using microdoses of psychedelic substances, i. e., subthreshold doses without noticeable effects on experience, which act predominantlyonthe serotonergic system. Twostudies using psilocybin³⁶ and LSD³⁷ detected deviations of timing performance under the influenceo fm icrodoses onlyf or intervals longer than2seconds.H owever,a ne ntire cocktail of neurochemical systems contributes to the experience of time.T he neurotransmitter GABA has been correlated with timing accuracy in the subsecond time range;³⁸ the neuromodulator oxytocin induced aspecific time dilation and compression effect for happy female and for happy male faces,r espectively,i nh eterosexual male viewers.³⁹ To sum up these elaborations, next to the above-mentioned involvement of several transmitter systems, multiple neural networks are involved in the processing of time on different time scales.⁴⁰ Recent neuroimaging studies point to several areas in the frontal cortex (SMA, inferior frontal gyrus), right intraparitetal sulcus, the basal ganglia, and the insula.⁴¹ One could arguet hat starting in  See Nani et al. (2020). the 1980ies researchers weretrying to find adedicated timing system, an internal clock in an eural network which would be solelyr esponsible for the processing of duration.What has emergedo vert he lastc ouple of years is the insight that there is not one mechanism or area in the brain responsible for encoding time, but that there is am anifold of brain functions which rely on general dynamic properties of neural circuits.⁴² From the distributed neural circuits with its intrinsic neural patterns of activity theremight be one circuitthat is predominantlyi nvolveda ccordingt om odality,t ask requirements, and the duration of the interval processed.⁴³ Alternatively, several of these neural circuits could work together in an integratedf ashion to cover different functional subcomponents for tracking time.⁴⁴ The heterogeneity of neural mechanisms and brain circuits explains whymanypatientswith avariety of diagnosed neurological disorders are often affected in the accuracy and precision of duration judgment.I n those patientg roups performance rarelyb reaks down completely, e. g., in patients with essential tremor who are diagnosed with anatomicallyw idespread cerebello-thalamocortical dysfunctions.⁴⁵ If one neural system is damaged, other parallel systems can partiallytake over and compensate.Timed behaviour is still possible, albeit impaired.

5I nteroception as the Basisf or the Experience of Time
In the following we focus on one functional and anatomical module of the brain related to interoceptive (bodily) awareness which, over the last few years, has been implicatedinthe processing of subjective time. We will discuss the connection between empirical results in the cognitive neurosciences on the relationship between time perception and interoception with phenomenologicallyi nspired ideas of temporale xperience.S tarting with the systematic analysis of Maurice Merleau-Ponty,i ndividual philosophers have held the idea that perception and action,i ncludings ubjective time and motor timing,a re embodied faculties of the mind. The further developments of the enactive/embodied cognition models of subjectivity accordingly claim that the phenomenal first-person perspective of experience and behaviour depends on the dynamics of the corporal self.⁴⁶ Aclassic studywas conducted by Martin Strack and his students (1988) which showed that feedback from facial muscles influencefelt emotions: Participants rated cartoons as funnier while they werepresented under the condition with apen in the mouth that facilitated muscles expressingp ositive emotions (a smile)a sc ompared to acondition whereapen inhibited smiling,i.e., apen facilitatedmuscles expressingn egative emotions. Subjective feelingsdepend upon bodily signals, i. e., visceral and somatosensory feedback from the peripheral nervous system, which informu sa bout the state of the body. Theses omatic signals are integratedw ith sensory signals from the others enses and with reference to the motivational, social and cognitive situation; in sum this integration capacity leadst othe conscious awareness of the momentary emotional condition of an individual.⁴⁷ One neural processing routeinthe multistep integration of ascendingsomatic signals culminatesinthe insular cortex, wherethe primary entry location for the signals is the dorsalposterior insula. Thisbrain region has been termed the primaryinteroceptivecortex, the primary area in the cortex to process signals from all bodilyo rgans.⁴⁸ The fact thatt he insula is richlyc onnected with other brain areas (limbic, sensorymotor)s ubstantiates the view that interoceptive (embodied)p rocesses underlie perception, cognition, and emotion.S everal studies have shown that the conscious awarenessofvisual stimuli depends on how close they occur to the heartbeat; the closer the external stimuli to the heart beat,the lower accuracy of perceptual detection. Fore xample, an euroimaging studys howed that the neural signals from the heart,asrecorded in the insula, suppressed visual information when it was presented too close to the heart beat.⁴⁹ Cardiac timing effects were also shown with emotional stimuli.F earful faces werej udgeda sm ore emotionallyarousingwhen photos werepresented at the cardiac systole (the actual heart beat) comparedt ow hent hey werep resented at the diastole (the relaxation period between heart beats); these effects were correlated with activity in the amygdala and insula.⁵⁰ The insular cortex contributes to the experience of duration in the sub-second and supra-second time domain as repeatedlydocumented in reviews of neuroimaging studies.⁵¹ In our own neuroimaging research we employed aduration  Ap rominent neurophenomenological approachi sp ut forwardb yV arela et al. (1991|2016).  See Damasio (1999). reproduction task with multiple-second tone intervals (3,9,18seconds) in which individuals are presented first with at one of varyingi nterval lengths (encoding phase) which subsequentlyh avet ob er eproduced in duration (reproduction phase).⁵² Ramp-likeincreases in fMRI activation was detected in the insular cortex which corresponded to stimulus duration. Activity ended with the termination of the to-be-timed stimuli in both the encoding( dorsal posterior insula) and the reproduction period (anteriorinsula). The very sameduration reproduction task alsop roved to be related to recorded bodysignals.Cardiac periods increased (the heart slowed down) and skin-conductance levels decreased (a sign of relaxation) progressively during encodingand the reproduction phases for au-ditory⁵³ and visual intervals.⁵⁴ In as imilar duration reproduction task, but with much shorter acoustic and visual stimuli (500 to 1500 ms), activity in mid-insula (encodingp hase) and the left anterior insula (reproduction phase) wasr eported.⁵⁵ The authors speculated thati nsula activity in this temporalt ask could be related to the feeling of time passage.
The feeling of time passingcould be used in sentient beingsasawaytotrack time. We will come backtothis idea alittle later.Recent work led by Alice Teghil convincingly pointst ot he involvement of interoceptive processes in the perception of time.Intheirbehaviouralstudytwo duration reproduction tasks with intervals lasting between 8a nd 18 seconds wereu sed, filled with (a) regular spaced and (b)w ith irregular spaced stimuli.⁵⁶ The regular condition thus provided external cues on presented duration which the irregular task did not. Onlyt iming accuracy of the duration reproduction task with irregular stimuli was predicted by trait-like interoceptive awareness assessed by the Self-Awareness Questionnaire. That is, the general ability to be more aware of somatic states helped subjects to be more accurate in time perception when no regular external signals werea vailable; they consequentlyh ad to relyo nt he dynamics of their bodilyself to judge duration. Thesefindingsare indicative of the assumption made abovet hat different distributed timing systems might come into play with different weights,across individuals but also within aperson depending on the task given. An inter-individual propensity to be more aware of bodilyp rocesses helpedsubjects to be more accurate in the timing task. With fewer external cues available subjects potentiallyh ad to rely more on internal signals.This interpretation is founded on as ubsequent studyb yA lice coworkers  See Wittmann et al. (2010), (2011).  See Meissner and Wittmann (2011).  See Otten et al. (2015).  See Bueti and Macaluso (2011).  See Teghil et al. (2020a). with the same durationr eproduction task, wheret hey showed that posterior insula connectivity,which was modulated by individual interoceptive awareness as measured with the Self-Awareness Questionnaire, correlated onlyw ith the irregular condition and not with the regular condition.⁵⁷ In ad ifferent study using dynamic video clips with intervals between 1a nd 64 seconds, duration estimatescould be explainedbythe amountofchanges in the contents shown in the scenes,and not by measured cardiac responses or eye recordings.⁵⁸ Participants in that studymight have used the accumulation of perceivede vents stored in workingm emory to deducee xperienced duration.These studies in combination show that, depending on the outward structure of the changingw orld, we can use visual or (acoustic) cues to deducet ime. Or,when these cues are absento ri rregular,wec an rely on our internal bodyc hanges to judge duration.
What happens when the insular cortex is neurologicallydamaged?I nasingle-case study, an epileptic patientw ho suffered from focal damaget ot he right anterior insula showed severe impairments in the timing of multiple-second time intervals in the above-mentionedd urationr eproduction task, an impairment that did not occur in epileptic patientsw ith damaget oo ther cortical regions.⁵⁹ Relating to duratione stimation of shorteri ntervals between 300 and 1500 ms, one studyr ecruited and tested twenty-one neurological patients with as troke in either the right or left insular cortex and compared performance with that of twenty-one control subjects.⁶⁰ Onlyp atients with right-hemispheric lesions, and not thosew ith left-hemispheric lesions, quiter emarkablyu nderestimated the presented durations.
Ac omprehensive account regardingt he relationship between awareness of bodilys tates, emotions and subjective time has been provided by Bud Craig (2009;2 015). Al ink between the three objects of awareness (body, emotions, and time) was proposed because the experience of time is related to emotional and visceral processes which share acommon underlying neural processing system, the interoceptive system which includes the insular cortex. Based on the constantlyo ngoing processing of ascendingb odilys ignals from the periphery and the internal organs as eries of conscious emotional moments is created over time. Our sense of the bodilyand emotional self is informed and constantly updated through ascending somatics ignals integrated in the insula (therefore Craig'sp rogrammatic book title "How do youf eel?"). Accordingly, the sense of time passagew ould evolve by the awareness of successive moments of bodily and emotional self-realizationwithin as ocial and cognitive context.I ne ssence, Craig presents an embodied theory of consciousness as grounded in the dynamic processes constituting the living body.

6P henomenological and Neurobiological
Accounts of Temporality What we want to put forward in the context of this chapter is thatH enri Bergson'sd ynamic view of consciousness as time constitutingc omplements to some extent the embodied model of time consciousness we present here. We are not discussingB ergson'sm etaphysical accounts of time⁶¹,b ut-similar to Barry Dainton's( 2017)a nalysis of Bergson-consider him as phenomenologist of time. Accordingt op henomenological analyses in the 20 th century (Husserl, Heidegger, Merleau-Ponty), self-consciousness and time-consciousness are inseparable. Conscious awarenessc an be described as an island of presencei n the continuous flow of what happens (Metzinger 2004). Conscious states are inherentlygiven to me; phenomenal experience is mine (Nagel1974). Time as continuous flow of events in the present moment is linked to someone who experiences something,i .e., conscious perception includes ab asic form of selfconsciousness (Zahavi 2005). The phenomenologicallyd educed unity of time and self can be expressed as: "there is no time without as elf; there is no self without time".⁶² Julian Kiverstein (2009) (Bergson 1917, 196). Or,asBarry Dainton puts it: "… when we hear asequence of notes unfolding as part of am elody, we not onlyh ear each note seamlessly flowing into the next,but the individual notes are themselvesinherentlydynamic" (Dainton 2017, 95). The phenomenological derivation of the unity of time consciousness and self-consciousness, includingi ts inherent dynamism, is strikingly similar to the neurophysiological model by Bud Craig wheret he constantlyo ngoing integration of somaticsignals over time generates afloating experience of the emotional self across moments of self-awareness. From an eurobiological perspective,t he underlying neural machinery at work actuallyp rocesses incoming bits of information in discrete steps as witnessed by brain oscillations with manydifferent lower and higher frequencies.⁶⁴ These neural oscillations underlie all cognitive functions including perceptual and motor timing.⁶⁵ Multiple oscillatory neural activities are however organized and interwoven into an integrated spatio-temporal continuum of brain activity. One idea is that slow cortical potentials,s panning several seconds of duration, mayg enerate the temporal width of experience, an extended present moment.⁶⁶ The long phases of these low-frequency fluctuations would temporallyintegrate oscillatory neural activity from different brain regions in order to enable conscious awareness and the feeling of an extended "now".Tojuxtapose the phenomenological view and the neuroscientific hypothesis of an extended present,one could state thatthe underlying neural machinery generatest he temporal platform of as ubjective present (Pöppel 2009), an island of presence ( Metzinger 2004). This extended present  See Buzsáki (2006).  See van Wassenhove( 2016); Roehricht et al. (2018).  See Northoff (2014).
Reinterpreting the Einstein-Bergson Debate moment constitutes the temporal frame within which the dynamic flow of perceivede vents happens over time leadingt oe xperienced temporality.⁶⁷ In his analysis of Bergson'sp hilosophyo ft emporality,D ainton (2017) sees strongevidence for an extensional account,a lthough some passages across different works could be interpreted differently, i. e., favoring ar etentional model. Dainton'selaboration of an extensional model suggests dynamic elements of experience within an extended moment and across (overlapping) extended moments which createt he seamless continuity of experience. In contrasting inner duration from the time measured by clocks, Henri Bergson similarlyw rites in his Essaie sur les données immédiates da la conscience (Time and Free Will) that "… inner duration, perceivedbyconsciousness,isnothing else but the melting of states of consciousness into one another" (Bergson 1913,107). In Dainton's (2017, 101) parlance of this stream-like structure: "Ai se xperienceda sf lowing into B, Bi se xperienced as flowing into C, and Ci nto D".
AccordingtoBergson experienced duration(la durée)isexperiential time as an intensive non-quantifiable entity: "psychic states seem to be more or less intense […]l ookedi nt heir multiplicity, they enfold in time and constituted uration" (Bergson 1917, 224). That is pure experience of temporality: "the deepest conscious states have no relation to quantity,t hey are pure quality" (Bergson 1917, 137). At al ater stages ubjective time mayb eq uantified,i .e., spatialized as "length of duration",b yc omparingp sychic states with external events, i. e., defined by clocks for measuring objective time. But the pure impression of temporality is generated through the qualitative stream-like enfolding of inner states.

Summary
The unity of time and self-consciousness has an inherent temporal dynamism as described by phenomenologists over the last 130 years. These phenomenological descriptions are mirrored by neurophysiologicalc onceptions, which postulate a similar interoceptive dynamismassociated with our feeling of time and self. It is suggested that the constantlyongoing temporal integration of somatic signals in the brain generates ad ynamic experience of the emotional self across moments of self-awareness.A ccordingly, the conscious feelingso fe motions, self-experience, and subjective time stem from the dynamismo ft he same neural system related to interoceptive processing.W eh ighlighted specific empirical evidence  See Dorato and Wittmann (2020). informed by recent neurophysiological studies showing that the experience of time is governedbyemotional and visceral processes which are based on the interoceptive processing system. Neuroimaging studies have repeatedlyshown that the insular cortex is activated when individuals have to judge duration in the millisecond and second range. Peripheral-physiological indices such as the heartrate or breathingrate are related to the accuracy in perception of timed external events as well as to the judgment of duration. Subjective assessments of interoceptive awarenesss how how people who are more aware of their bodily condition are alsom orea ccurate in time perception. Henri Bergson is thereafter vindicated as he was right to emphasize the dynamismo ft he temporals elf as becoming. Psychologyand cognitiveneurosciencehavecome to asimilar,scientifically-inspired, conclusion. Seen under this perspective also AlbertE instein was right.Bergson'sa pproach was actuallyp sychological in the sense that psychologyi si nformed by phenomenology.