Sense of time

The sense of time can refer either to the perception of relatively short periods of time, or the perception of times which are a significant fraction of a person's lifetime.

When asked to place the time of a past event, people have a systematic tendency to recall that recent events occurred farther back in time (backward telescoping) and distant events occurred more recently (forward telescoping) than is actually the case.

Experiments have shown rats successfully estimating intervals of time.

Theory
William J. Friedman contrasted two theories for a sense of time: Unfortunately, the trace model comes into conflict with a very familiar feature of our experience: that some memories of recent events may fade more quickly than memories of more distant events.
 * The strength model of time memory. Posits such a thing as a memory trace that persists over time, where one could judge the age of a memory (and therefore how long ago the event remembered occurred) from the strength of the trace. The longer ago the event, the weaker the trace.
 * The inference model suggests the time of an event is not simply read off from some aspect of the memory of it, but is inferred from information about relations between the event in question and other events whose date or time is known.

Short-term
Although the sense of time is not associated with a specific sensory system, the work of psychologists and neuroscientists indicates that human brains do have a system governing the perception of time. This is a highly distributed system including the cerebral cortex, cerebellum and basal ganglia as its components. One particular component, the suprachiasmatic nuclei, is responsible for the circadian (or daily) rhythm, while other cell clusters appear to be capable of shorter-range (ultradian) timekeeping. The sense of time is impaired in some people with neurological diseases such as Parkinson's disease and attention deficit disorder.

Human perception of duration is subjective and variable. For example, time may appear to slow or drag as one eagerly anticipates the arrival of a specific event. A school day may seem endless for a student who is waiting for the bell indicating that school is finished for the day. The traditional proverb describing this effect is "a watched pot never boils".

Psychoactive drugs can also alter the perception of time. Stimulants can lead both humans and rats to overestimate time intervals while depressants can have the opposite effect. The level of activity in the brain of neurotransmitters such as dopamine and adrenaline may be the reason for this. Errors in estimated time intervals might be caused by varying levels of neurotransmitters in the brain.

People who have been hypnotized underestimate the duration of their trance.

In an experiment comparing a group of subjects aged between 19 and 24 and a group between 60 and 80 asked to estimate when they thought 3 minutes had passed, it was found that the younger group's estimate was on average 3 minutes and 3 seconds, while the older group averaged 3 minutes and 40 seconds, indicating a change in the perception of time with age.

Specious present
The specious present is the time duration wherein a state of consciousness is experienced as being in the present. The term specious present was first introduced by the psychologist E. R. Clay, and developed by William James. 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. The experienced present is an interval; it's not a momentary instant except 'speciously'.

Long-term
It is a known phenomenon that long periods of time appear to pass faster as people grow older. The time from a child's eighth birthday to the ninth seems an eternity; the time from the sixty-eighth to the sixty-ninth seems to pass in a flash.

Alterations
A form of temporal illusion verifiable by experiment is the kappa effect, whereby time intervals between visual events are perceived as relatively longer or shorter depending on the relative spatial positions of the events. In other words: the perception of temporal intervals appears to be directly affected, in these cases, by the perception of spatial intervals.

Special relativity
This common experience was used to familiarize the general public to the ideas presented by Einstein's theory of relativity in a 1930 cartoon by Sidney "George" Strube:

Psychoactive substances
Altered states of consciousness are sometimes characterized by a different estimation of time. Some psychoactive substances – such as entheogens – may also dramatically alter a person's temporal judgement. When viewed under the influence of such substances as LSD, psychedelic mushrooms, and peyote, a clock may appear to be a strange reference point and a useless tool for measuring the passage of events as it does not correlate with the user's experience. At higher doses, time may appear to slow down, stop, speed up, go backwards and even seem out of sequence. 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 me".