Time Perception

Time perception refers to the subjective experience of the duration or temporal organization of events within a given period of time. In this entry, a brief overview of time perception is provided, including the main phenomena and models used to interpret them. The main neurobiological substrates of timing identified in recent studies are then presented.

Various types of temporal experience can be distinguished: the main types being perception of duration of events or stimuli, perception of order (which between a and b came first or second), and perception of temporal regularity or rhythm. These phenomena can take place on different time scales, varying from a few milliseconds to seconds, hours, days, and even years. For example, musical rhythm is perceived with a series of tones separated by temporal intervals shorter than about 2 seconds, and natural rhythms are perceived in succession of days, months, or years. Perceiving duration, order, and [Page 743]temporal regularity is fundamental in most activities for organisms evolving in a changing environment. Classical Pavlovian conditioning experiments as well as later experiments on animal timing demonstrated that pigeons, rats, and many other nonhuman species adapt remarkably to temporal contingencies of the environment, displaying highly developed abilities in interval timing and revealing a key role of temporal associations in learning. Things that are judged to be close in time tend to be associated, and this link constitutes the basis of learning in humans and other animals. Estimating time and processing temporal order are also essential in performing complex activities requiring coordination in movements or action, anticipation of times of occurrence in a dynamic environment, or remembering ordered elements like digits in phone numbers or words in sentences. In addition to being intimately related to most common activities involving planning, coordination, and memory, the ability to estimate time is also essential in rhythmic activities such as playing music or dancing.

A stopwatch is an efficient mechanism for estimating duration: It starts and ends at distinct moments, and the amount of temporal information accumulated between these two points constitutes an objective assessment of the interval bounded by the two points. Humans can quite accurately perform that kind of interval timing without any external time-keeping device. Interval timing is flexible in that it can start and stop any time in response to the demands of the environment, in contrast to rhythmic timing, such as in circadian rhythms, which is often determined by rather rigid constraints and shows relatively small variability. The phenomena, methods, and models described below mostly concern human interval timing in the few hundred milliseconds to minutes range.