Time perception

Time perception is a field of study within psychology, cognitive linguistics[1] and neuroscience that refers to the subjective experience, or sense, of time, which is measured by someone's own perception of the duration of the indefinite and unfolding of events.[2][3] The perceived time interval between two successive events is referred to as perceived duration. Though directly experiencing or understanding another person's perception of time is not possible, such a perception can be objectively studied and inferred through a number of scientific experiments. Time perception is a construction of the sapient brain, but one that is manipulable and distortable under certain circumstances. These temporal illusions help to expose the underlying neural mechanisms of time perception.

Pioneering work, emphasizing species-specific differences, was conducted by Karl Ernst von Baer.[4]

In other words time can be perceived or understood as Subjective Time & Objective Time.

Swatch Irony angle below
A contemporary quartz watch

Theories

William J. Friedman (1993) also contrasted two theories for a sense of time:[5][6][7]

  • The strength model of time memory. This posits a memory trace that persists over time, by which one might judge the age of a memory (and therefore how long ago the event remembered occurred) from the strength of the trace. This conflicts with the fact that memories of recent events may fade more quickly than more distant memories.
  • The inference model suggests the time of an event is inferred from information about relations between the event in question and other events whose date or time is known.

Another theory involves the brain's subconscious tallying of "pulses" during a specific interval, forming a biological stopwatch. This theory alleges that the brain can run multiple biological stopwatches at one time depending on the type of task one is involved in. The location of these pulses and what these pulses actually consist of is unclear.[8] This model is only a metaphor and does not stand up in terms of brain physiology or anatomy.[9]

Philosophical perspectives

The specious present is the time duration wherein a state of consciousness is experienced as being in the present.[10] The term was first introduced by the philosopher E. R. Clay in 1882 (E. Robert Kelly),[11][12] and was further developed by William James.[12] James defined the specious present to be "the prototype of all conceived times... the short duration of which we are immediately and incessantly sensible". In "Scientific Thought" (1930), C. D. Broad further elaborated on the concept of the specious present and considered that the specious present may be considered as the temporal equivalent of a sensory datum.[12] A version of the concept was used by Edmund Husserl in his works and discussed further by Francisco Varela based on the writings of Husserl, Heidegger, and Merleau-Ponty.[13] Although he lived prior to these modern philosophers, Hasidic master Rabbi Nachman of Breslov (1772-1810) discussed the nature and perception of time in various teachings. He remarked that only the present day and present moment are "real," [14] and also noted that a person could sleep for fifteen minutes and dream that he or she had lived seventy years.[15]

Neuroscientific perspectives

Although the perception of time is not associated with a specific sensory system, psychologists and neuroscientists suggest that humans do have a system, or several complementary systems, governing the perception of time.[16] Time perception is handled by a highly distributed system involving the cerebral cortex, cerebellum and basal ganglia.[17] One particular component, the suprachiasmatic nucleus, is responsible for the circadian (or daily) rhythm, while other cell clusters appear to be capable of shorter (ultradian) timekeeping. There is some evidence that very short (millisecond) durations are processed by dedicated neurons in early sensory parts of the brain[18][19]

Professor Warren Meck devised a physiological model for measuring the passage of time. He found the representation of time to be generated by the oscillatory activity of cells in the upper cortex. The frequency of these cells' activity is detected by cells in the dorsal striatum at the base of the forebrain. His model separated explicit timing and implicit timing. Explicit timing is used in estimating the duration of a stimulus. Implicit timing is used to gauge the amount of time separating one from an impending event that is expected to occur in the near future. These two estimations of time do not involve the same neuroanatomical areas. For example, implicit timing often occurs to achieve a motor task, involving the cerebellum, left parietal cortex, and left premotor cortex. Explicit timing often involves the supplementary motor area and the right prefrontal cortex.[9]

Two visual stimuli, inside someone's field of view, can be successfully regarded as simultaneous up to five milliseconds.[20][21][22]

In the popular essay "Brain Time", David Eagleman explains that different types of sensory information (auditory, tactile, visual, etc.) are processed at different speeds by different neural architectures. The brain must learn how to overcome these speed disparities if it is to create a temporally unified representation of the external world: "if the visual brain wants to get events correct timewise, it may have only one choice: wait for the slowest information to arrive. To accomplish this, it must wait about a tenth of a second. In the early days of television broadcasting, engineers worried about the problem of keeping audio and video signals synchronized. Then they accidentally discovered that they had around a hundred milliseconds of slop: As long as the signals arrived within this window, viewers' brains would automatically resynchronize the signals". He goes on to say that "This brief waiting period allows the visual system to discount the various delays imposed by the early stages; however, it has the disadvantage of pushing perception into the past. There is a distinct survival advantage to operating as close to the present as possible; an animal does not want to live too far in the past. Therefore, the tenth-of- a-second window may be the smallest delay that allows higher areas of the brain to account for the delays created in the first stages of the system while still operating near the border of the present. This window of delay means that awareness is retroactive, incorporating data from a window of time after an event and delivering a delayed interpretation of what happened."[23]

Experiments have shown that rats can successfully estimate a time interval of approximately 40 seconds, despite having their cortex entirely removed.[24] This suggests that time estimation may be a low level process.[25]

Types of temporal illusions

A temporal illusion is a distortion in the perception of time. Time perception refers to a variety of time-related tasks. For example:

  • estimating time intervals, e.g., "When did you last see your primary care physician?";
  • estimating time duration, e.g., "How long were you waiting at the doctor's office?"; and
  • judging the simultaneity of events (see below for examples).

Short list of types of temporal illusions:

  • Telescoping effect: People tend to recall recent events as occurring further back in time than they actually did (backward telescoping) and distant events as occurring more recently than they actually did (forward telescoping).[26]
  • Vierordt's law: Shorter intervals tend to be overestimated while longer intervals tend to be underestimated
  • Time intervals associated with more changes may be perceived as longer than intervals with fewer changes
  • Perceived temporal length of a given task may shorten with greater motivation
  • Perceived temporal length of a given task may stretch when broken up or interrupted
  • Auditory stimuli may appear to last longer than visual stimuli[27][28][29][30]
  • Time durations may appear longer with greater stimulus intensity (e.g., auditory loudness or pitch)
  • Simultaneity judgments can be manipulated by repeated exposure to non-simultaneous stimuli

Kappa effect

The Kappa effect or perceptual time dilation[31] is a form of temporal illusion verifiable by experiment,[32] wherein the temporal duration between a sequence of consecutive stimuli is thought to be relatively longer or shorter than its actual elapsed time, due to the spatial/auditory/tactile separation between each consecutive stimuli. The kappa effect can be displayed when considering a journey made in two parts that take an equal amount of time. Between these two parts, the journey that covers more distance may appear to take longer than the journey covering less distance, even though they take an equal amount of time.

Eye movements and "Chronostasis"

The perception of space and time undergoes distortions during rapid saccadic eye movements[33]

Chronostasis is a type of temporal illusion in which the first impression following the introduction of a new event or task demand to the brain appears to be extended in time.[34] For example, chronostasis temporarily occurs when fixating on a target stimulus, immediately following a saccade (e.g., quick eye movement). This elicits an overestimation in the temporal duration for which that target stimulus (i.e., postsaccadic stimulus) was perceived. This effect can extend apparent durations by up to 500 ms and is consistent with the idea that the visual system models events prior to perception.[35] The most well-known version of this illusion is known as the stopped-clock illusion, wherein a subject's first impression of the second-hand movement of an analog clock, subsequent to one's directed attention (i.e., saccade) to the clock, is the perception of a slower-than-normal second-hand movement rate (the seconds hand of the clock may seemingly temporarily freeze in place after initially looking at it).[36][37][38][39]

The occurrence of chronostasis extends beyond the visual domain into the auditory and tactile domains.[40] In the auditory domain, chronostasis and duration overestimation occur when observing auditory stimuli. One common example is a frequent occurrence when making telephone calls. If, while listening to the phone's dial tone, research subjects move the phone from one ear to the other, the length of time between rings appears longer.[41] In the tactile domain, chronostasis has persisted in research subjects as they reach for and grasp objects. After grasping a new object, subjects overestimate the time in which their hand has been in contact with this object.[37] In other experiments, subjects turning a light on with a button were conditioned to experience the light before the button press.

Oddball effect

The perception of the duration of an event seems to be modulated by our recent experiences. Humans typically overestimate the perceived duration of the initial event in a stream of identical events[42] and unexpected “oddball” stimuli seem to be perceived as longer in duration, relative to expected or frequently presented “standard” stimuli.[43]

The oddball effect may serve an evolutionarily adapted “alerting” function and is consistent with reports of time slowing down in threatening situations. The effect seems to be strongest for images that are expanding in size on the retina, in other words, that are "looming" or approaching the viewer,[43][44][45] and the effect can be eradicated for oddballs that are contracting or perceived to be receding from the viewer.[44] The effect is also reduced[43] or reversed[45] with a static oddball presented amongst a stream of expanding stimuli.

Initial studies suggested that this oddball-induced “subjective time dilation” expanded the perceived duration of oddball stimuli by 30–50%[43] but subsequent research has reported more modest expansion of around 10%[45][46][47][48] or less.[49] The direction of the effect, whether the viewer perceives an increase or a decrease in duration, also seems to be dependent upon the stimulus used.[49]

Effects of emotional states

Awe

Research has suggested the feeling of awe has the ability to expand one's perceptions of time availability. Awe can be characterized as an experience of immense perceptual vastness that coincides with an increase in focus. Consequently, it is conceivable that one's temporal perception would slow down when experiencing awe.[50]

Fear

Possibly related to the oddball effect, research suggests that time seems to slow down for a person during dangerous events (such as a car accident, a robbery, or when a person perceives a potential predator or mate), or when a person skydives or bungee jumps, where they're capable of complex thoughts in what would normally be the blink of an eye (See Fight-or-flight response).[51] This reported slowing in temporal perception may have been evolutionarily advantageous because it may have enhanced one's ability to intelligibly make quick decisions in moments that were of critical importance to our survival.[52] However, even though observers commonly report that time seems to have moved in slow motion during these events, it is unclear whether this is a function of increased time resolution during the event, or instead an illusion created by the remembering of an emotionally salient event.[53]

A strong time dilation effect has been reported for perception of objects that were looming, but not of those retreating, from the viewer, suggesting that the expanding discs — which mimic an approaching object — elicit self-referential processes which act to signal the presence of a possible danger.[54] Anxious people, or those in great fear, experience greater "time dilation" in response to the same threat stimuli due to higher levels of epinephrine, which increases brain activity (an adrenaline rush).[55] In such circumstances, an illusion of time dilation could assist an efficacious escape.[56][57] When exposed to a threat, three-year-old children were observed to exhibit a similar tendency to overestimate elapsed time.[9][58]

Research suggests that the effect appears only at the point of retrospective assessment, rather than occurring simultaneously with events as they happened.[59] Perceptual abilities were tested during a frightening experience — a free fall — by measuring people's sensitivity to flickering stimuli. The results showed that the subjects' temporal resolution was not improved as the frightening event was occurring. Events appear to have taken longer only in retrospect, possibly because memories were being more densely packed during the frightening situation.[59]

People shown extracts from films known to induce fear often overestimated the elapsed time of a subsequently presented visual stimulus, whereas people shown emotionally neutral clips (weather forecasts and stock market updates) or those known to evoke feelings of sadness showed no difference. It is argued that fear prompts a state of arousal in the amygdala, which increases the rate of a hypothesized "internal clock". This could be the result of an evolved defensive mechanism triggered by a threatening situation.[60]

Empathy

The perception of another persons' emotions can also change our sense of time. The theory of embodied mind (or cognition), caused by mirror neurons, helps explain how the perception of other people's emotions has the ability to change one's own sense of time. Embodied cognition hinges on an internal process that mimics or simulates another's emotional state. For example, if person #1 spends time with person #2 who speaks and walks incredibly slowly, person #1's internal clock may slow down.

Depression

Depression may increase one's ability to perceive time accurately. One study assessed this concept by asking subjects to estimate the amount of time that passed during intervals ranging from 3 seconds to 65 seconds.[61] Results indicated that depressed subjects more accurately estimated the amount of time that had passed than non-depressed patients; non-depressed subjects overestimated the passing of time. This difference was hypothesized to be because depressed subjects focused less on external factors that may skew their judgment of time. The authors termed this hypothesized phenomenon "depressive realism."[61]

Changes with age

Psychologists have found that the subjective perception of the passing of time tends to speed up with increasing age in humans. This often causes people to increasingly underestimate a given interval of time as they age. This fact can likely be attributed to a variety of age-related changes in the aging brain, such as the lowering in dopaminergic levels with older age; however, the details are still being debated.[62][63][64] In an experimental study involving a group of subjects aged between 19 and 24 and a group between 60 and 80, the participants' abilities to estimate 3 minutes of time were compared. The study found that an average of 3 minutes and 3 seconds passed when participants in the younger group estimated that 3 minutes had passed, whereas the older group's estimate for when 3 minutes had passed came after an average of 3 minutes and 40 seconds.[65][66]

Very young children literally "live in time" before gaining an awareness of its passing. A child will first experience the passing of time when he or she can subjectively perceive and reflect on the unfolding of a collection of events. A child's awareness of time develops during childhood when the child's attention and short-term memory capacities form — this developmental process is thought to be dependent on the slow maturation of the prefrontal cortex and hippocampus.[9][67]

One day to an 11-year-old would be approximately 1/4,000 of their life, while one day to a 55-year-old would be approximately 1/20,000 of their life. This helps to explain why a random, ordinary day may therefore appear longer for a young child than an adult.[68] The short term appears to go faster in proportion to the square root of the perceiver's age.[69] So a year would be experienced by a 55-year-old as passing approximately 2¼ times more quickly than a year experienced by an 11-year-old. If long-term time perception is based solely on the proportionality of a person's age, then the following four periods in life would appear to be quantitatively equal: ages 5–10 (1x), ages 10–20 (2x), ages 20–40 (4x), age 40–80 (8x).[68]

The common explanation is that most external and internal experiences are new for young children but repetitive for adults. Children have to be extremely engaged (i.e. dedicate many neural resources or significant brain power) in the present moment because they must constantly reconfigure their mental models of the world to assimilate it and manage behaviour properly. Adults however may rarely need to step outside mental habits and external routines. When an adult frequently experiences the same stimuli, they seem "invisible" because they have already been sufficiently and effectively mapped by the brain. This phenomenon is known as neural adaptation. Thus, the brain will record fewer densely rich memories during these frequent periods of disengagement from the present moment.[70] Consequently, the subjective perception is often that time passes by at a faster rate with age.

Effects of drugs

Stimulants produce overestimates of time duration, whereas depressants and anaesthetics produce underestimates of time duration.

Psychoactive drugs can alter the judgment of time. These include traditional psychedelics such as LSD, psilocybin, and mescaline as well as the dissociative class of psychedelics such as PCP, ketamine and dextromethorphan. At higher doses time may appear to slow down, speed up or seem out of sequence. In a 2007 study, psilocybin was found to significantly impair the ability to reproduce interval durations longer than 2.5 seconds, significantly impair synchronizing motor actions (taps on a computer keyboard) with regularly occurring tones, and impair the ability to keep tempo when asked to tap on a key at a self-paced but consistent interval.[71] In 1955, British MP Christopher Mayhew took mescaline hydrochloride in an experiment under the guidance of his friend, Dr Humphry Osmond. On the BBC documentary The Beyond Within, he described that half a dozen times during the experiment, he had "a period of time that didn't end for [him]".

Stimulants can lead both humans and rats to overestimate time intervals,[72][73] while depressants can have the opposite effect.[74] The level of activity in the brain of neurotransmitters such as dopamine and norepinephrine may be the reason for this.[75] Dopamine has a particularly strong connection with one's perception of time. Drugs that activate dopamine receptors speed up one's perception of time, while dopamine antagonists cause one to feel that time is passing slowly.[9][76]

The effect of cannabis on time perception has been studied with inconclusive results.

Effects of body temperature

Time perception may speed up as body temperature rises, and slow down as body temperature lowers. This is especially true during stressful events.[77]

Reversal of temporal order judgment

Numerous experimental findings suggest that temporal order judgments of actions preceding effects can be reversed under special circumstances. Experiments have shown that sensory simultaneity judgments can be manipulated by repeated exposure to non-simultaneous stimuli. In an experiment conducted by David Eagleman, a temporal order judgment reversal was induced in subjects by exposing them to delayed motor consequences. In the experiment, subjects played various forms of video games. Unknown to the subjects, the experimenters introduced a fixed delay between the mouse movements and the subsequent sensory feedback. For example, a subject may not see a movement register on the screen until 150 milliseconds after the mouse had moved. Participants playing the game quickly adapted to the delay and felt as though there was less delay between their mouse movement and the sensory feedback. Shortly after the experimenters removed the delay, the subjects commonly felt as though the effect on the screen happened just before they commanded it. This work addresses how the perceived timing of effects is modulated by expectations, and the extent to which such predictions are quickly modifiable.[78] In an experiment conducted by Haggard and colleagues in 2002, participants pressed a button that triggered a flash of light at a distance after a slight delay of 100 milliseconds.[79] By repeatedly engaging in this act, participants had adapted to the delay (i.e., they experienced a gradual shortening in the perceived time interval between pressing the button and seeing the flash of light). The experimenters then showed the flash of light instantly after the button was pressed. In response, subjects often thought that the flash (the effect) had occurred before the button was pressed (the cause). Additionally, when the experimenters slightly reduced the delay, and shortened the spatial distance between the button and the flash of light, participants had often claimed again to have experienced the effect before the cause.

Several experiments also suggest that temporal order judgment of a pair of tactile stimuli delivered in rapid succession, one to each hand, is noticeably impaired (i.e., misreported) by crossing the hands over the midline. However, congenitally blind subjects showed no trace of temporal order judgment reversal after crossing the arms. These results suggest that tactile signals taken in by the congenitally blind are ordered in time without being referred to a visuospatial representation. Unlike the congenitally blind subjects, the temporal order judgments of the late-onset blind subjects were impaired when crossing the arms to a similar extent as non-blind subjects. These results suggest that the associations between tactile signals and visuospatial representation is maintained once it is accomplished during infancy. Some research studies have also found that the subjects showed reduced deficit in tactile temporal order judgments when the arms were crossed behind their back than when they were crossed in front.[80][81][82]

Flash-lag effect

In an experiment, participants were told to stare at an "x" symbol on a computer screen whereby a moving blue doughnut-like ring repeatedly circled the fixed "x" point.[83][84][85] Occasionally, the ring would display a white flash for a split second that physically overlapped the ring's interior. However, when asked what was perceived, participants responded that they saw the white flash lagging behind the center of the moving ring. In other words, despite the reality that the two retinal images were actually spatially aligned, the flashed object was usually observed to trail a continuously moving object in space — a phenomenon referred to as the flash-lag effect.

The first proposed explanation, called the 'motion extrapolation' hypothesis, is that the visual system extrapolates the position of moving objects but not flashing objects when accounting for neural delays (i.e., the lag time between the retinal image and the observer's perception of the flashing object). The second proposed explanation by David Eagleman and Sejnowski, called the 'latency difference' hypothesis, is that the visual system processes moving objects at a faster rate than flashed objects. In the attempt to disprove the first hypothesis, David Eagleman conducted an experiment in which the moving ring suddenly reverses direction to spin in the other way as the flashed object briefly appears. If the first hypothesis were correct, we would expect that, immediately following reversal, the moving object would be observed as lagging behind the flashed object. However, the experiment revealed the opposite — immediately following reversal, the flashed object was observed as lagging behind the moving object. This experimental result supports of the 'latency difference' hypothesis. A recent study tries to reconcile these different approaches by approaching perception as an inference mechanism aiming at describing what is happening at the present time.[86]

Effects of clinical disorders

Parkinson's disease,[87] schizophrenia,[88] and attention deficit hyperactivity disorder (ADHD)[89] have been linked to abnormalities in dopamine levels in the brain as well as to noticeable impairments in time perception. Neuropharmacological research indicates that the internal clock, used to time durations in the seconds-to-minutes range, is linked to dopamine function in the basal ganglia.[88] Studies in which children with ADHD are given time estimation tasks shows that time passes very slowly for them. Children with Tourette’s Syndrome, in contrast, who need to use the pre-frontal cortex to help them control their tics, are better at estimating intervals of time just over a second than other children.

In his book Awakenings, the neurologist Dr. Oliver Sacks discussed how patients with Parkinson's disease experience deficits in their awareness of time and tempo. For example, Mr E, when asked to clap his hands steadily and regularly, did so for the first few claps before clapping faster and irregularly, culminating in an apparent freezing of motion. When he finished, Mr E asked if his observers were glad he did it correctly, to which they replied "no". Mr E was offended by this because to him, his claps were regular and steady.[90]

Dopamine is also theorized to play a role in the attention deficits present with attention deficit hyperactivity disorder. Specifically, dopaminergic systems are involved in working memory and inhibitory processes, both of which are believed central to ADHD pathology.[89] Children with ADHD have also been found to be significantly impaired on time discrimination tasks (telling the difference between two stimuli of different temporal lengths) and respond earlier on time reproduction tasks (duplicating the duration of a presented stimulus) than controls.[91]

Along with other perceptual abnormalities, it has been noted by psychologists that schizophrenia patients have an altered sense of time. This was first described in psychology by Minkowski in 1927.[92] Many schizophrenic patients stop perceiving time as a flow of causally linked events. It has been suggested that there is usually a delay in time perception in schizophrenic patients compared to normal subjects.

These defects in time perception may play a part in the hallucinations and delusions experienced by schizophrenic patients according to some studies. Some researchers suggest that "abnormal timing judgment leads to a deficit in action attribution and action perception."[92]

Sleep

The perception of time is temporarily suspended during sleep, or more often during REM sleep. This can be attributed to the altered state of consciousness associated with sleep that prevents awareness of the surroundings, which would make it difficult to remain informed of the passing of time — new memories are rarely made during sleep. Therefore, upon waking up in the morning a person subjectively feels no time has passed but reasons that many hours have elapsed simply because it is now light outside. The passing of time must be inferred by observations of objects (e.g., the sun’s location, the moon, a clock's time) relative to the previous evening. So, time may feel as passing "faster" during sleep due to the lack of reference points. Another experience sometimes reported is a long dream seeming to go on for hours when it actually lasted only a few seconds or minutes.[93]

See also

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Further reading

External links

Cannabis and time perception

The effect of cannabis on time perception has been studied with inconclusive results. Studies show consistently throughout the literature that most cannabis users self-report the experience of a slowed perception of time. In the laboratory, researchers have confirmed the effect of cannabis on the perception of time in both humans and animals. Studies have sought to explain how cannabis changes the internal clock. Matthew et al. (1998) looked at the cerebellum, positing a relationship between cerebellar blood flow and the distortion of time perception.

Chronometry

Chronometry (from Greek χρόνος chronos, "time" and μέτρον metron, "measure") is the science of the measurement of time, or timekeeping. Chronometry applies to electronic devices, while horology refers to mechanical devices.

It should not to be confused with chronology, the science of locating events in time, which often relies upon it.

Color psychology

color psychology' is the study of hues as a determinant of human behavior. Color influences perceptions that are not obvious, such as the taste of food. Colors can also enhance the effectiveness of placebos. For example, red or orange pills are generally used as stimulants. Color can indeed influence a person; however, it is important to remember that these effects differ between people. Factors such as gender, age, and culture can influence how an individual perceives color. For instance, heterosexual men tend to report that red outfits enhance female attractiveness, while heterosexual females deny any outfit color impacting that of men.

Color psychology is also widely used in marketing and branding. Many marketers see color as an important part of marketing because color can be used to influence consumers' emotions and perceptions of goods and services. Companies also use color when deciding on brand logos. These logos seem to attract more customers when the color of the brand logo matches the personality of the goods or services, such as the color pink being heavily used on Victoria's Secret branding. Colors are also important for window displays in stores. Research shows that warm colors tended to attract spontaneous purchasers, despite cooler colors being more favorable.

Common year

A common year is a calendar year with 365 days, as distinguished from a leap year, which has 366. More generally, a common year is one without intercalation. The Gregorian calendar, (like the earlier Julian calendar), employs both common years and leap years to keep the calendar aligned with the tropical year, which does not contain an exact number of days.

The common year of 365 days has 52 weeks and one day, hence a common year always begins and ends on the same day of the week (for example, January 1 and December 31 fell on a Sunday in 2017) and the year following a common year will start on the subsequent day of the week. In common years, February has four weeks, so March will begin on the same day of the week. November will also begin on this day.

In the Gregorian calendar, 303 of every 400 years are common years. By comparison, in the Julian calendar, 300 out of every 400 years are common years, and in the Revised Julian calendar (used by Greece) 682 out of every 900 years are common years.

Darren Rhodes (scientist)

Darren Rhodes is a Scientist at the University of Sussex investigating the perception of time, consciousness and multisensory experience. Rhodes' is a strong proponent of Bayesian Time Perception. He is currently working on an EU FET program TimeStorm where he is determining the foundational principles of time perception in humans and artificial systems.

David Eagleman

David Eagleman (born April 25, 1971) is an American neuroscientist, author, and science communicator. He teaches as an adjunct professor at Stanford University and is CEO of NeoSensory, a company that develops devices for sensory substitution. He also directs the non-profit Center for Science and Law, which seeks to align the legal system with modern neuroscience. He is known for his work on brain plasticity, time perception, synesthesia, and neurolaw. He is a Guggenheim Fellow and a New York Times bestselling author published in 32 languages. He is the writer and presenter of the Emmy-nominated international television series, The Brain with David Eagleman.

Eternity

Eternity in common parlance is an infinitely long period of time. In classical philosophy, however, eternity is defined as what exists outside time while sempiternity is the concept that corresponds to the colloquial definition of eternity.

Eternity is an important concept in many religions, where the god or gods are said to endure eternally. Some, such as Aristotle, would say the same about the natural cosmos in regard to both past and future eternal duration, and like the eternal Platonic forms, immutability was considered essential.

HD2IOA

HD2IOA is the callsign of a time signal radio station operated by the Navy of Ecuador. The station is located at Guayaquil, Ecuador and transmits in the HF band on 3.81 and 7.6 MHz.The transmission is in AM mode with only the lower sideband (part of the time H3E and the rest H2B/H2D) and consists of 780 Hz tone pulses repeated every ten seconds and voice announcements in Spanish.

While sometimes this station is described as defunct, reception reports of this station on 3.81 MHz appear regularly at the Utility DX Forum.

Intercalation (timekeeping)

Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months.

Karl von Vierordt

Karl von Vierordt (July 1, 1818 – November 22, 1884) was a German physiologist.

Vierordt was born in Lahr, Baden. He studied at the universities of Berlin, Göttingen, Vienna, and Heidelberg, and began a practice in Karlsruhe in 1842. In 1849 he became a professor of theoretical medicine at the University of Tübingen, and in 1853 a professor of physiology.

Vierordt developed techniques and tools for the monitoring of blood circulation. He is credited with the construction of an early "hemotachometer", an apparatus for monitoring the velocity of blood flow. In 1854, he created a device called a sphygmograph, a mechanism consisting of weights and levers used to estimate blood pressure, and considered to be a forerunner of the modern sphygmomanometer. One of his better known written works was a treatise on the arterial pulse, titled Die Lehre vom Arterienpuls in gesunden und kranken Zuständen.

Vierordt also made substantial contributions to the psychology of time perception, via his book (published in 1868) Der Zeitsinn nach Versuchen, "The experimental study of the time sense". This reported a large number of experiments on the perception of duration, with the time sense being considered a "general sense" along with the perception of space, in contrast to the "special senses" such as vision and hearing. Included in this book is discussion of, and evidence for, what has come to be known as Vierordt's Law: roughly the proposition that short durations tend to be overestimated, while long durations tend to be underestimated.

Between these two extremes is a "point of indifference" where the "time sensation", in Vierordt's terminology, corresponds exactly to physical time. However, the 1868 book does much more than report this "law" and contains extensive discussions of different methods used to measure duration perception, as well as different sorts of errors that can occur.

Although Vierordt was not the first person to carry out experiments on time perception, his 1868 book involved much more extensive experimentation and discussion than had been carried out until then.

He died in Tübingen, aged 66.

Kush (cannabis)

Kush is a strain of Cannabis indica. The origins of Kush Cannabis are from landrace plants mainly in Afghanistan, Northern Pakistan and North-Western India with the name coming from the Hindu Kush mountain range. "Hindu Kush" strains of Cannabis were taken to the United States in the mid-to-late 1970s and continue to be available there to the present day.Kush strains were among those cultivated by the British firm GW Pharmaceuticals for its legally licensed commercial trial of medicinal cannabis.

Minute

The minute is a unit of time or angle. As a unit of time, the minute is most of times equal to ​1⁄60 (the first sexagesimal fraction) of an hour, or 60 seconds. In the UTC time standard, a minute on rare occasions has 61 seconds, a consequence of leap seconds (there is a provision to insert a negative leap second, which would result in a 59-second minute, but this has never happened in more than 40 years under this system). As a unit of angle, the minute of arc is equal to ​1⁄60 of a degree, or 60 seconds (of arc). Although not an SI unit for either time or angle, the minute is accepted for use with SI units for both. The SI symbols for minute or minutes are min for time measurement, and the prime symbol after a number, e.g. 5′, for angle measurement. The prime is also sometimes used informally to denote minutes of time.

Savart wheel

The Savart wheel is an acoustical device named after the French physicist Félix Savart (1791–1841), which was originally conceived and developed by the English scientist Robert Hooke (1635–1703).A card held to the edge of a spinning toothed wheel will produce a tone whose pitch varies with the speed of the wheel. A mechanism of this sort, made using brass wheels, allowed Hooke to produce sound waves of a known frequency, and to demonstrate to the Royal Society in 1681 how pitch relates to frequency. For practical purposes Hooke's device was soon supplanted by the invention of the tuning fork.

About a century and a half after Hooke's work, the mechanism was taken up again by Savart for his investigations into the range of human hearing. In the 1830s Savart was able to construct large, finely-toothed brass wheels producing frequencies of up to 24 kHz that seem to have been the world's first artificial ultrasonic generators. In the later 19th century, Savart's wheels were also used in physiological and psychological investigations of time perception.

Nowadays, Savart wheels are commonly demonstrated in physics lectures, sometimes driven and sounded by an air hose (in place of the card mechanism).

Specious present

The specious present is the time duration wherein one's perceptions are considered to be in the present. Time perception studies the sense of time, which differs from other senses since time cannot be directly perceived but must be reconstructed by the brain.

Tachypsychia

Tachypsychia is a neurological condition that alters the perception of time, usually induced by physical exertion, drug use, or a traumatic event. For someone affected by tachypsychia, time perceived by the individual either lengthens, making events appear to slow down, or contracts, objects appearing as moving in a speeding blur.It is generally believed that tachypsychia is induced by a combination of high levels of dopamine and norepinephrine, usually during periods of great physical stress or in violent confrontation.

Time

Time is the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past, through the present, to the future. Time is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience. Time is often referred to as a fourth dimension, along with three spatial dimensions.Time has long been an important subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars.

Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems.Time in physics is unambiguously operationally defined as "what a clock reads". See Units of Time. Time is one of the seven fundamental physical quantities in both the International System of Units and International System of Quantities. Time is used to define other quantities – such as velocity – so defining time in terms of such quantities would result in circularity of definition. An operational definition of time, wherein one says that observing a certain number of repetitions of one or another standard cyclical event (such as the passage of a free-swinging pendulum) constitutes one standard unit such as the second, is highly useful in the conduct of both advanced experiments and everyday affairs of life. The operational definition leaves aside the question whether there is something called time, apart from the counting activity just mentioned, that flows and that can be measured. Investigations of a single continuum called spacetime bring questions about space into questions about time, questions that have their roots in the works of early students of natural philosophy.

Temporal measurement has occupied scientists and technologists, and was a prime motivation in navigation and astronomy. Periodic events and periodic motion have long served as standards for units of time. Examples include the apparent motion of the sun across the sky, the phases of the moon, the swing of a pendulum, and the beat of a heart. Currently, the international unit of time, the second, is defined by measuring the electronic transition frequency of caesium atoms (see below). Time is also of significant social importance, having economic value ("time is money") as well as personal value, due to an awareness of the limited time in each day and in human life spans.

Time travel

Time travel is the concept of movement between certain points in time, analogous to movement between different points in space by an object or a person, typically using a hypothetical device known as a time machine. Time travel is a widely-recognized concept in philosophy and fiction. The idea of a time machine was popularized by H. G. Wells' 1895 novel The Time Machine.

It is uncertain if time travel to the past is physically possible. Forward time travel, outside the usual sense of the perception of time, is an extensively-observed phenomenon and well-understood within the framework of special relativity and general relativity. However, making one body advance or delay more than a few milliseconds compared to another body is not feasible with current technology. As for backwards time travel, it is possible to find solutions in general relativity that allow for it, but the solutions require conditions that may not be physically possible. Traveling to an arbitrary point in spacetime has a very limited support in theoretical physics, and usually only connected with quantum mechanics or wormholes, also known as Einstein-Rosen bridges.

Tomorrow (time)

Tomorrow is a temporal construct of the relative future; literally of the day after the current day (today), or figuratively of future periods or times. Tomorrow is usually considered just beyond the present and counter to yesterday. It is important in time perception because it is the first direction the arrow of time takes humans on Earth.

Vierordt's law

Karl von Vierordt (1868) was the first to record a law of time perception which relates perceived duration to actual duration over different interval magnitudes, and according to task complexity.

Vierordt's law is "a robust phenomenon in time estimation research that has been observed with different time estimation methods". It states that, retrospectively, "short" intervals of time tend to be overestimated, and "long" intervals of time tend to be underestimated. The other major paradigm of time estimation methodology measures time prospectively.

Key concepts
Measurement and
standards
Clocks
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  • Mythology
Philosophy of time
Human experience
and use of time
Time in
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