Chronophobia is a specific psychological phobia which manifests itself as a persistent, abnormal and unwarranted fear of time or of the passing of time. A related but much rarer phobia is chronomentrophobia, the irrational fear of clocks and watches.
Like many other phobias, the main symptoms include panic, unease, depression, anxiety, and often a feeling of claustrophobia (of being closed in, with no escape). In some more serious cases, individuals may experience shaking, shortness of breath, excessive sweating, irregular heartbeats, even sickening states of mind, inability to articulate words, tunnel vision and overwhelmingly haunting thoughts.
Sufferers may be aware of a vague feeling that events are moving too fast and running away with themselves, and that it is difficult to make sense of the way events are unfolding. Chronophobia is often marked by a sense of derealization in which time seems to speed up or slow down, and some people may develop circular thought patterns, racing thoughts and symptoms of obsessive-compulsive disorder.
Who Does It Affect
Chronophobia is most often experienced by two main groups: the elderly, and by those incarcerated in prison (where it also known as prison neurosis). The elderly tend to have a lot of idle time on their hands, and often time drags very slowly for them. Perhaps unsurprisingly, it is common for old people, particularly those facing terminal illnesses, to be hyper-aware of their imminent death (death anxiety), and this constant threat of death can cause an overwhelming sensation of chronophobia. As people get older, their metabolism and brain functions slow down, making them even more susceptible to chronophobia. Prison inmates also tend to have extensive periods of unstructured time, which may lead them to excessive contemplation of the passing of time, the length of time of their sentence, the number of days remaining until their release, etc. They also typically experience high levels of anxiety and stress due to their circumstances, which puts them especially at risk.
Chronophobia may also affect another much smaller population: shipwreck survivors, survivors of natural disasters, and others who are trapped in a high-anxiety situation with no familiar means of tracking the passage of time. It may also be caused by a traumatic experience during childhood, or by some genetic disorder (such as adrenal insufficiency, where the adrenal glands do not produce adequate amounts of hormones such as cortisol or aldosterone, which tends to make a person more susceptible to anxiety and fear). It occasionally appears with no apparent cause, though this is relatively rare.
Chronophobia cannot really be prevented as such, but stress relief techniques (such as avoiding stressful or anxiety-producing situations, participating in meditation, yoga, tai chi, etc) may alleviate the symptoms to some extent. Cognitive-behavioral therapy, hypnotherapy or acupuncture may be effective treatments in some cases, and a method of psychotherapy known as neuro-linguistic programming has also shown some promise.
Medications to calm the nerves may have some short-term value, but they often have unpleasant side effects, and do not actually erase the fear but merely suppress the symptoms.
A temporal illusion is a distortion in the perception of time that occurs for various reasons, such as due to different kinds of stress. In such cases, a person may momentarily perceive time as slowing down, stopping, speeding up, or even running backwards, as the timing and temporal order of events are misperceived. When we say that time slows down, what we actually mean is that our internal clock speeds up, which gives the impression that time in the rest of the world slows down.
The kappa effect is a form of temporal illusion which can be verified by experiment. It refers to occasions when the temporal duration between a sequence of consecutive stimuli is thought to be relatively longer or shorter than its actual elapsed time, as a result of the spatial separation between consecutive stimuli.
As an example, if three light sources are flashed successively in the dark with equal time intervals between each of the flashes, the temporal interval between the two light sources that are closer together tends to be perceived to be shorter than that between the two light sources that are further away from each other (even though the time intervals are actually equal). As another example, if two consecutive journeys take an equal amount of time, the journey that covers more distance may appear to the individual perceiver as taking longer than the journey covering less distance, even though they actually take an equal amount of time.
Several theories have been put forward to explain the kappa effect, mainly based on the brain’s prior expectations about stimulus velocity or speed. It seems that the brain is wired to expect temporal intervals that would produce constant velocity (i.e. uniform motion). There is a related spatial illusion called the tau effect, where the spatial separation between stimuli is constant and the temporal separation is varied (as might indeed be expected if the explanation of the effects concerns expected velocity).
Chronostasis, also known as the stopped clock illusion, is where the first impression following the introduction of a new event or task demand to the brain appears to be extended in time. The most commonly encountered example is when the second hand of an analog clock appears to freeze in place for a short period of time after a person initially looks at it. A similar illusion can also be found within the auditory system.
It appears to occur as a result of a disconnect in the communication between visual sensation and perception, specifically triggered by quick eye movements (technically known as saccades) which can disrupt this flow of information, although research is still ongoing and the complete mechanism is still not well understood.
To some extent, though, this is just an exaggerated example of a more commonly experienced phenomenon (see the Oddball Effect below). Psychological testing has shown that reactions to exposure to ANY new auditory or visual stimuli take longer than reactions to known or repeated stimuli, suggesting an internal slowing down of time perception, perhaps to accommodate increased brain arousal, activity and attention.
The so-called “oddball effect” occurs when the brain experiences something unusual or out of the normal run of events. In this case, the brain pays special attention and spends more time processing the event, recording as much information as possible on the novel circumstances, which can lead to a feeling that time has slowed down.
This is particularly apparent when a person perceives an unusual or stressful sensory stimulus, particularly one that appears to be a potential threat or a possible mate. For example, time seems to slow down when a person skydives or bungee jumps, or when a person suddenly and unexpectedly senses the presence of a potential predator or mate. Similar effects occur when emotions of fear are artificially generated by watching a horror film. It is thought that changes in the neurotransmitter norepinephrine (adrenaline) is responsible for this slowing down our internal clock.
There may be an evolutionarily advantage to such a response, in that it may enhance our ability to make quick and good decisions in moments that may be of critical importance to our survival (or procreation), where one has a short space of time in which to decide whether to attack or run away (fight or flight). To a bystander watching a life-threatening situation such as an accident, time is moving at a normal speed, but the individual in the accident may perceive time as having slowed down, allowing them “more” time to think and act during these potentially life-threatening events. David Eagleman has carried out experiments that show quite clearly that, in high adrenaline situations, the brain is actually capable of processing information significantly faster than under normal circumstances.
However, it is still not completely clear whether the effect is actually a function of a real increase in time resolution during the event, or just an illusion ofmemory of emotionally important or salient events. It looks increasing probable that it may only be a retrospective assessment that brings a person to feel that time ran in slow motion during a life-threatening or stressful event. More specifically, the brain does its best to record everything possible about a stressful, threatening or exciting situation in memory, in case they may be useful in future situations. The more memories that are accumulated about the situation, the more data there is to subsequently “leaf through”, giving the impression that more time must have passed.
Positive or negative emotions can affect the subjective perception of time. “Time flies” is a common proverbial expression, since its first appearance in Vergil’s Georgics in 29BCE as “tempus fugit” (literally “time flees”). It is particularly commonly encountered in the phrase ”time flies when you are having fun”, which refers to the way that time seems to pass very quickly, and without notice, when one is otherwise occupied with something enjoyable. The key here seems to be partly that one is not attending to, or consciously thinking about, the passing time, but also that the underlying emotion is one of happiness and enjoyment, particularly enjoyment with a motivation or a goal. A tedious or unpleasant task, on the other hand, appears to take a disproportionately long time to complete.
Even the perception of another person’semotions can be enough to slightly change our sense of time. The neurological mechanism here may be quite different, though, resting on a process called embodied cognition (an internal process that mimics or simulates another’s emotional state) and mirror neurons (a neuron that fires both when a person acts and when they observe the same action performed by another).
Unexpectedly and perhaps counter-intuitively, studies have shown that sensory deprivation (such as in experimental isolation chambers) tends to compress the experience of time, so that minutes, hours and days seem to pass about twice as fast as usual. Time spent under these unpleasant and undeniably tedious conditions paradoxically feels shorter than normal time, and some other effect seems to be at work here.
The subjective perception of the passing of time tends to speed up with increasing age in humans. Older people often complain that the years (and even the days) pass much more quickly than they used to. This same effect also causes older people to underestimate given intervals of time. For example, one study showed how estimates of a 3 minute period among a group of 19-24 year olds yielded an average of 3 minutes 3 seconds, while the estimates of a group of 60-80 year olds averaged 3 minutes 40 seconds.
Various explanations for this common experience have been put forward, including: the fact that younger people are still living through new and interesting (rather than repeated and routine) experiences, requiring more neural resources and brain power, and are less subject to the neural adaptation experienced by older people; the fact that a single day (or an hour) represents a much larger proportion of the lives of young people as compared to older people; the general slowing down of most organic processes in the bodies of older people; the lower dopamine levels in the ageing brain; etc. It may even be that our internal biological clocks slow down in some way as we age.
Very young children appear to have little or no conception of the passing of time, which is thought to be due to the continuing maturation of the prefrontal cortex and hippocampus in young children.
The brain’s judgement of time can be affected and impaired by various psychoactive drugs. This probably occurs because of the way such drugs affect level of activity in the brain of neurotransmitters such as dopamine and norepinephrine. They either excite or inhibit the firing of neurons in the brain, with a greater firing rate allowing the brain to register the occurrence of more events within a given interval (so that time seems to slows down), and a decreased firing rate reducing the brain’s capacity to distinguish events occurring within a given interval (time speeds up).
For example, stimulants (or “uppers”), which are typically intended to enhance alertness, wakefulness and locomotion, tend to lead to an overestimation of time intervals as time seems to slow down for the user. Caffeine, nicotine, amphetamines, cocaine, etc, are examples of stimulants. On the other hand depressants (or “downers”), which typically decrease arousal and mental/physical function, have the opposite effect, as time seems to speed up and time intervals may be underestimated. Alcohol, cannabis, heroin and other opioids are all depressants.
Neuroscientist Warren Meck has carried out experiments with trained rats to demonstrate how drugs affect the rats’ internal clocks and their estimation of time periods. Rats on cocaine perceived a 12-second period as being around 8 seconds, while rats on marijuana estimated about 16 seconds for the same period.
Experiments have even been carried out to ascertain whether it is possible to use drugs to “speed up” our mental processes relative to a duration of physical time, thus making us more mentally productive and effectively allowing us to learn more per minute. However, none of these experiments have yielded any success yet.
Given its emphasis on moment-to-moment awareness, it seems logical that mindfulness meditation (which purports to improve attention, working memory capacity, and reading comprehension, among other things) would alter time perception to some extent, and experiments have indeed shown that it may lead to a relative overestimation of time durations.
Some studies have shown that time perception may speed up as body temperature rises, and slow down as body temperature lowers. The neural and physiological mechanisms for such an effect are unclear.
Medical conditions that result in, or are caused by, abnormal dopamine levels in the brain (e.g. Parkinson’s disease, schizophrenia, attention deficit hyperactivity disorder, etc) may be linked to noticeable impairments in time perception. For example, in time estimation tasks, children with ADHD feel that time passes very slowly for them. Some Parkinson’s patients find it difficult to clap to a regular beat, despite their own perception of having completed the task quite effectively. Schizophrenic patients may stop perceiving time as a flow of causally linked events, and there is often a delay in time perception in schizophrenic patients compared to normal subjects.
The brain’s internal clock, which is typically used to time durations in the seconds-to-minutes range, has been shown to be specifically linked to dopamine function in the basal ganglia region of the brain, so it is perhaps no surprise that dopamine abnormalities might affect time perception in this interval range.
Some autistic savants have an incredibly developed and accurate sense of the passage of time, and may be able to tell the exact time to the minute at any point in the day or night, or to state exactly how much time has passed, without looking at (or even being able to read) a clock.
We have various metabolic processes within our bodies that are to some extent “clock-like” (i.e. repetitive and predictable – see the section on Clocks), e.g. heart beats, breathing, etc. But these processes are dependent on other conditions and stimuli, both internal and external, and are not reliably regular (e.g. heartbeats and breathing rates can speed or up slow down depending on our activities, health, environment, etc). But we do have some internal biological clocks that are much more reliable, autonomous and self-supporting, and one in particular is found throughout the natural world.
Many essential biological processes and activities in living organisms observe more or less regular daily variations in their timing and duration (e.g. eating, sleeping, hormone production, cellular regeneration, etc, in animals; leaf movements, photosynthetic reactions, etc, in plants; etc). Humans,
and almost all life on Earth, from animals to plants to fungi, right down to single-celled organisms, have adapted themselves to the 24-hour light/dark day/night cycle of our planet.
Whether diurnal or nocturnal, the behavioural patterns of almost all life follow this daily cycle by means of a circadian clock, an endogenous (internal) time-keeper with a period of approximately 24 hours (the word “circadian” comes from the Latin words meaning “about a day”). Indeed, so similar is this mechanism throughout the spectrum of life, that it seems likely to have evolved from a single genetic code rather than through convergent evolution. Circadian clocks can be found even in primitive bacteria and other microbial organisms, and are among the evolutionarily oldest features of living organisms.
Interestingly, just like the artificial clocks we construct for our own timekeeping purposes, the basic mechanism of these biological clocks relies to a large extent on oscillation, using negative feedback loops, with hormones and neurons working in concert to achieve the required balance or homeostasis, and to prevent progress too far in one direction or another.
The circadian clocks of plants were first discovered in the 18th Century, and the great Swedish naturalist Carl Linnaeus designed a “floral clock” in 1751 on which the time was indicated by various flowers that bloomed at different times of the day. Photoperiodism, the physiological reaction of organisms to the length of day or night, is vital to both plants and animals, and the circadian system plays an important role in the measurement and interpretation of day length.
In animals, the circadian clock is physically located in a tiny pinhead-sized area known as the suprachiasmatic nucleus in the hypothalamus region of the basal forebrain, one of the most evolutionarily ancient parts of the brain. There is one nucleus in each hemisphere of the brain, and so collectively they are referred to as the suprachiasmatic nuclei.
Although containing just 20,000 or so very small neurons, the suprachiasmatic nuclei are responsible for the overall circadianrhythms that the body perceives internally, and with regulating sleeping and feeding patterns, alertness, core body temperature, brain wave activity, hormone production (including melatonin and cortisol, which are so important in sleep regulation), glucose and insulin levels, urine production, cell regeneration, and many other biological activities. For instance, it maintains wakefulness by sending out alerting pulses throughout the day (to counteract the other element of our biological sleep regulation process, the homeostatic sleep pressure that gradually builds up during the day), and then weakens the alerting pulses and increases melatonin production in the late evening in order to open up the so-called “sleep gate”.
The circadian clock itself is adjusted or entrained to the environment by external cues, known as Zeitgebers (a German word meaning “time-givers”). The most important of these Zeitgebers is daylight and the daily light/dark cycle, information about which is transmitted to the suprachiasmatic nuclei via specialized ganglion cells in the eyes. The circadian clock uses these Zeitgebers to naturally synchronize or reset itself each day to within just a few minutes of the Earth’s 24-hour rotation cycle.
Interestingly, the individual neurons that make up the suprachiasmatic nuclei have been found to exhibit a near-24-hour rhythm of activity, suggesting that the clock mechanism actually works on a sub-cellular level. When dissociated from the brain, the individual cells follow their own intrinsic 24-hour rhythms, but, when incorporated into the suprachiasmatic nuclei, they all start to fire in perfect synchrony. In addition to this basic mechanism, the circadian rhythms of mammals are also encoded in a number of genes, including the PER or period gene, which work in complex interactions with the brain and the rest of the body.
In actual fact, individual circadian periods among humans do vary slightly, dependent on variations in the person’s PER gene, ranging between about 23.5 and 24.5 hours, with a mean of around 24.2 hours (just slightly more than the Earth’s rotation period). About 25% of people have a natural circadian period which is slightly less than the 24-hour day, and the other 75% have a circadian period slightly more than 24 hours. Individuals also have a chronotype, and some people (often known as “larks” or morning people) tend to wake up early and are most alert during the first part of the day, like many older people, while others (“night owls” or evening people) are most alert in the late evening and prefer to go to bed late, like many teenagers.
Peripheral Biological Clocks
There are also other secondary or peripheral biological clocks throughout the body, such as in the liver, heart, pancreas, kidneys, lungs, intestines, and even in the skin and lymphocytes, all of which show natural daily oscillations. Many of these secondary biological clocks are entrained independently by Zeitgebers like the timing of meals, ambient temperatures, exercise, etc, rather than by the light-dark cycle, but the central coordination and synchronization is still carried out by the suprachiasmatic nuclei.
Scientists working with mice have recently found evidence of a food-entrainable biological clock, which is not controlled by the suprachiasmatic nucleus. The exact location of this clock is still not clear, but it may be located in the dorsomedial hypothalamus area of the brain.
Still other cell clusters regulate shorter-period ultradian rhythms (cycles of less than a day), such as the 90-minute REM sleep cycle, the 4-hour nasal cycle, and the 3-hour cycle of growth hormone production. There are also infradian rhythms (cycles longer than a day), such as the monthly human menstrual cycle, and the annual migration, hibernation or reproduction cycles of certain animals and birds. Famously, some colonies of cicadas have a unique thirteen or seventeen year birth cycle.
A whole field of study has arisen within biology in recent decades called chronobiology, which looks at, and seeks to use, the periodic or cyclic biological rhythms of living organisms and their adaptation to external rhythms and cycles. Scientists have realized that timing medical treatments to coincide with specific points in these cycles can enhance the effectiveness of the treatments.
The severity of many diseases often also varies across the 24-hour period, e.g. heart attacks occur most often in the morning, a few hours after waking up; temporal lobe epileptic seizures usually occur in the late afternoon or early evening; asthma is generally worst at night; etc. Understanding the biological basis of these changes across the day and night may provide an insight into the underlying cause of the diseases, and could lead to better therapy.
Perhaps the most obvious application of chronobiology is in the treatment of some sleep disorders, as well as temporary conditions like jet lag The use of light therapy and melatonin administration at specific times of day can be used as a means of resetting circadian rhythms, and thereby affecting sleep patterns. Other possible uses of chronobiological research are in the timing of the intake of calories and sodium in a person’s diet, and in the timing of drug and radiotherapy treatments.
Time is not directly perceived, and so time perception is essentially a construction of the brain, which can therefore be manipulated and distorted in various ways (see the section on Temporal Illusions). Biopsychology, also sometimes known as behavioural neuroscience or psychobiology, studies the way the brain (at the level of nerves, neurotransmitters, brain circuitry and basic biological processes) does that.
Although another person’s perception of time obviously cannot be directly experienced or understood, there are techniques within psychology and neuroscience that can allow us to objectively study the phenomenon.
The actual mechanism by which the brain perceives and processes the concept of time is complex and not fully understood. The judgement and perception of time is known to involve different part of the brain in a highly distributed system, and the cerebral cortex, cerebellum and basal ganglia are all involved to some extent. However, experiments on rats that have had their cortexes completely removed show that they can still successfully estimate a time interval of about 40 seconds, suggesting that time estimation may actually be a more low-level or sub-cortical process.
Neurotransmitters such as dopamine and norepinephrine (adrenaline) are integrally involved in our perception of time, although the exact mechanism is still not well understood. Some neuropharmacological research indicates that the human brain possesses some kind of “internal clock” (distinct from the biological or circadian clock), that is typically used to time durations in the seconds-to-minutes range. This timing mechanism appears to be specifically linked to dopamine function in the basal ganglia region of the brain, and norepinephrine also serves to slow down our internal clock (as do some drugs – see the section on Temporal Illusions).
Neuroscientist Warren Meck has carried out experiments showing how specific neurons near the base of the brain become active when a person is asked to estimate a duration of time. Neurochemicals are released by these cells that trigger other cells in the frontal cortex, which is what allows us to judge the passing of time. Meck also believes that the brain may have several different clocks working together but independently, and that the brain selects a “winner” from these different possible timings depending on the context.
In experiments with rats in conditions of sensory deprivation, psychologist Howard Eichenbaum discovered that certain neurons in the hippocampus region of the brain (an area important in memory function among other things) seem to fire in sequence almost like the ticking of a clock. For example, some cells fired when the rat first enters the sensory deprivation area, some in the next second, some in the third second, some in the fourth, etc. Over extended periods, some cells drop out of the “ticking”, some fire at different times, and some that were not firing earlier begin to fire. Eichenbaum has called these neurons “time cells”, similar to the “place cells” which are also found in the hippocampus (i.e. some cells seem to respond mostly to distance or location, while some respond mostly to time).
Delays in Time Perception
Although thought and perception appear to take no time at all, they are nevertheless constrained by the speed of neurological processes (e.g. the time for signals to leap across synapses, for action potentials to move along the axons of neurons, etc). The brain processes different types of sensory information (e.g. auditory, tactile, visual, etc) at different speeds using different neural architectures. But it appears to be able to overcome these speed disparities in order to achieve a temporally unified representation of the outside world, through a process sometimes referred to as temporal binding. As an example, if touch our nose and our toes at the same time, the signal from our distant toes must take longer to arrive at the brain than the signal from our nearby nose, but we perceive them as occurring simultaneously.
The brain also uses this process, also known as integration, to integrate our sense of time into a seamless and fluid experience. This works in a similar way to the way in which the brain makes our sense perceptions of the outside world into a complete and unitary picture, glossing over any discontinuities and inconsistencies (e.g. the way we perceive a smoothly-moving movie, rather than a series of discrete and separate frames, and the way we can usually piece together meaning from a partially heard sentence).
Neuroscientists have found that our brain actually waits about 80 milliseconds for all the relevant input to come in before we experience a “now”, rather like a time delay in broadcasting “live” television or radio. So, if the discrepancy in time between different inputs is less than about one-tenth of a second, the brain is able to process the different sensory input together. If two images are flashed in fast enough succession, therefore, we are not able to tell which came first and which second. To use a real-world example, so long as television audio and video signals are synchronized to within one-tenth of a second, viewers’ brains are able to automatically re-synchronize the signals; any more of a delay and a mis-synchronization becomes noticeable.
There is an increasing body of research suggesting that the brain operates on some kind of an expected order and speed of events, and alterations to these expectations may lead to illusions like the kappa effect (see the section on Temporal Illusions). One study has shown how, when a video game player becomes used to a slight delay in computer mouse reaction time, and that delay is then removed, they may even experience a reversal in temporal perception judgement, feeling as though the effect on the screen happened just before they commanded it.
Other studies have shown that, when a pair of tactile stimuli are delivered to each hand in rapid succession, and the subject then crosses their arms across the body’s midline, they may experience the order of the stimuli as reversed. Interestingly, this reversing effect was not observed among congenitally blind subjects (as opposed to late-onset blind subjects), suggesting that the brain has a whole set of tactile/visual/spatial associations as regards time perception, which it develops during childhood.
Tests have shown that a person under hypnosis can judge time more accurately than the same person in a normal waking state. Unconscious time perception may therefore actually be more accurate than conscious time perception, possibly due to the lack of trained or conditioned responses and expectations that are present in the conscious state.
The speed of neuron firing in the brain is also of interest to psychologists and neuroscientists for other reasons.
Mental chronometry is a technique used in experimental and cognitive psychology to assess how fast an individual can execute certain mental operations. This involves measuring a person’s reaction time, i.e. the elapsed time between the presentation of a sensory stimulus and their subsequent behavioural response, typically the pressing of a button or sometimes an eye movement or vocal response. This can then be used as a measure of cognitive processing speed and efficiency, from which an assessment of the person’s general intelligence or IQ can be made. Mental chronometry techniques are also used in other areas of cognitive and behavioural neuroscience and psychophysiology.
Time perception refers to a person’s subjective experience of the passage of time, or the perceived duration of events, which can differ significantly between different individuals and/or in different circumstances. Although physical time appears to be more or less objective, psychological time is subjective and potentially malleable, exemplified by common phrases like “time flies when you are having fun” and “a watched pot never boils”. This malleability is made particularly apparent by the various temporal illusions we experience.
As a field of study within psychology and neuroscience, time perception came of age in the late 19th Century with the studies of the relationship between perceived and measured time by one of the founders of modern experimental psychology, Gustav Theodor Fechner.
We do not so much perceive time itself, but changes in or the passage of time, or what might be described as “events in time”. In particular, we are aware of the temporal relations between events, and we perceive events as being either simultaneous or successive. We also have a perception of the sequence or order of these events.
Our sense of time seems to have originated as a product of human evolution, and it is not a purely automatic or innate process, but a complex activity that we develop and actively learn as we grow. Humans are, as far as we know, the only animals to be consciously aware of the passage of time and our own impermanence and mortality, and to have a consciousness of the past that is anything more than pure instinct and behavioural conditioning.
How We Perceive Time
Although psychologists believe that there is a neurological system governing the perception of time, it appears not to be associated with specific sensory pathways, but rather uses a highly distributed system in the brain (see the section on Biopsychology). Time perception therefore differs from our other senses – sight, hearing, taste, smell, touch, even proprioception – since time cannot be directly perceived, and so must be “reconstructed” in some way by the brain.
Neurotransmitters such as dopamine and norepinephrine (adrenaline) are integrally involved in our perception of time, although the exact mechanism is still not well understood. The human brain appears to possess some kind of “internal clock” (distinct from the biological or circadian clock) which is linked to specific dopamine levels, or possibly even several different clocks working together but independently, each of which may dictate our time perception depending on the particular context (see the section on Biopsychology for more detail).
When the brain receives new information from the outside world, the raw data does not necessarily arrive in the order needed to process it properly. The brain therefore reorganizes the information and presents it in a more easily understandable form. In the case of familiar information, very little time is needed for this process, but new information requires more processing and this extra processing tends to makes time feel elongated. This is part of the reason why a child’s summer seems to last forever, while an old person’s well-practiced routine seems to slip away faster and faster. The more familiar the task, the less new information the brain needs to process, and the more quickly time seems to pass.
To some extent also, the perception of time is associated with other cognitive processes such as attention. Measuring the duration of an event – whether it be the length of time to leave a sauce to simmer, estimating how fast to run to catch a ball, or calculating whether there is enough time to drive through a yellow light – requires a certain amount of attention, and new events appear to take longer than familiar events because more attention is paid to them. For instance, in psychological tests, if the same picture is shown again and again, interspersed every so often with a different picture, the different picture is perceived by the observer as staying on-screen for longer, even if all the pictures actually appear for the same length of time. The difference arises from the degree of attention paid to the pictures.
The perception of time durations is also crucially bound up with memory. It is essentially our memory of an event (and perhaps, even more specifically, our memory of the beginning and end of the event) that allows us to form a perception of, or a belief in, its duration. We infer, albeit subconsciously, the duration of an event from our memory of how far in the past something occurred, of how long ago the beginning and end of the event occurred. It is not clear whether this is done by some measure of the strength of a memory trace that persists over time (thestrength model of time memory), or by an inference based on associations between the event and other events whose date or time is known (the inference model).
There is increasing evidence that an animal’s metabolic rate affects the way it perceives time. In general, larger animals have a slower metabolic rate, and time passes relatively rapidly for them. Smaller animals, conversely, tend to have faster metabolisms, and experience time as passing relatively slowly, so that they can perceive more events in the same period. Studies have shown that small animals can in fact distinguish very short and very quick-changing events, which is one reason why a fly can avoid a swatter with such apparent ease. In evolutionary terms, the ability to perceive time on very small scales may be the difference between life and death for small, vulnerable animals.
Sequence and Duration
We perceive time as series of events in a sequence, separate by durations of various lengths. Our experience is not limited to a single series of events, though, but we experience a plurality of overlapping events, sequences and durations.
A metronome ticking at a rate of two or three times a second is perceived as an integral sequence, as a rhythm. When the ticks are less frequent, though, say at intervals of three seconds, the sounds appears to be no longer perceived as a sequence in the same way, and each sound impulse remains an isolated perceptual event. Similar results occur with slowed down speech or music: music or spoken sentences are only recognizable as such when their rhythmic patterns and phrases are presented at an optimal speed that allow them to be recognized as a perceptual unity.
The perception of a duration requires a minimum of about 0.1 seconds in the case of visual stimuli such as a flash, or much less (0.01 to 0.02 seconds) in the case of auditory stimuli. Stimuli of any shorter time than these are therefore perceived as instantaneous, and as not representing any duration at all.
Various aspects of time – whether it is absolute or relative, real or unreal, etc – have been discussed in some detail in the sections on Philosophy of Time and Physics of Time. Here, however, we turn to matters of how an individual experiences and perceives time, and here things become even less definite and concrete.
Time perception refers to the subjective experience of the passage of time, or the perceived duration of events, which can differ significantly between different individuals and/or in different circumstances. Although physical time appears to be more or less objective, psychological time is subjective and potentially malleable.
The biopsychology of our perception of time is a fascinating but little understood area of psychology and neuroscience. It looks at the way our brain processes time and time intervals, and the brain’s built-in expectation of the order and speed of events, as well as the field of mental chronometry.
Most organisms have an internal sense of time generated by endogenous biological clocks, completely independent of ambient temperatures, sunlight, etc. The best known of these is the circadian clock, which maintains daily biological rhythms and regulates sleep, hormone production, etc, but there are also other peripheral biological clocks, some of which follow ultradian or infradian rhythms. A whole field of chronobiology has grown up to exploit our increasing knowledge of these biological rhythms.
Temporal illusions are distortions and misperceptions of time that arise from a variety of psychological and other causes. The most commonly encountered examples are the effects of ageing and psychoactive drugs on time perception, but there are several other interesting effects, such as the kappa effect, the stopped clock illusion, the oddball effect, etc.
Chronophobiais the fear of time or the passing of time, a specific and well-documented psychologicalphobia which principally affects the elderly and those incarcerated in prisons.