The word duration refers to a length of time and can be broadly categorized into two types. A filled (or full) interval is the length of time of a single event (such as a speech). An unfilled (or empty) interval is the length of time between two successive events (such as two knocks on a door).
Human perception of time is sometimes referred to as involving both duration and succession. In this case, succession is defined as the fact that two or more events are perceived as different and occurring in a sequence. Duration is defined as the interval between the successive events. Duration is not a thing by itself, but it is a quality or characteristic. Without succession, there is no duration.
For events having an extremely brief duration, the perception of instantaneity is created. In this case, the perceiver is unable to distinguish between the beginning and the end of the occurrence. Studies have found differing thresholds at which humans can perceive a duration, but the minimum threshold is usually around 130 microseconds.
A number of variables can affect how humans perceive a specific duration, as shown in many clinical studies. Circumstances that cause strong negative emotions seem to last longer, because of the additional attention focused on processing the emotional stimuli. This effect is known as the filled interval illusion. Other factors that may make an event appear longer include using auditory (rather than visual) stimuli, greater intensity of a sound or light stimulus, and use of filled intervals (rather than unfilled intervals).
The theory of cognitive orientation states that events with greater variability and unpredictability also appear longer. This is because the participant is not able to anticipate what is coming next, and it takes longer to become oriented to the situation.
It should be noted that perception of duration differs from estimation of duration. When humans estimate a duration, they are considering an event that has already occurred and is in the past. When humans perceive a duration, they are considering an event that is presently occurring.
Duration in Music
In musical notation, duration refers to the length of time that a note is held. In this case, a note’s duration is not absolute but rather relative to the whole note. For example, a half note has half of the duration of a whole note. The absolute duration of each note in a given piece is determined by the metronome marking (if given) and time signature. The time signature is made up of two numbers, one showing the number of beats per measure, and the other showing which note gets one beat.
The metronome marking is listed as a single number, indicating the number of beats per minute. In place of a metronome marking, some composers may use a tempo mark, which is a word or phrase indicating how fast or slow the music should feel. With this type of marking, the tempo is somewhat open to the interpretation of the conductor or performer.
Although much research about duration involves small periods of time, the word duration can also refer to lengthier events. For example, the age of the universe has been estimated at 13.7 billion years. One could see this time period as a filled interval (i.e., the duration during which the universe has existed). In this case, as the universe continues to exist, the duration will become longer, as there has not yet been an end point.
See also Bergson, Henri; Consciousness; Music; Perception; Spacetime Continuum; Time, Subjective Flow of
Cooper, G., & Meyer, L. B. (1960). The rhythmic structure of music. Chicago: University of Chicago Press.
Fraisse, P. (1984). Perception and estimation of time. Annual Review of Psychology, 35, 1-36.