The theory of the proportionality of time is a psychological concept that explains why the subjective perception of the passage of time changes with age, making the years seem to pass faster and faster. Its roots date back to the 19th-century reflections of the French philosopher Paul Janet, who first presented it in 1877; it was subsequently popularized and expanded upon by the eminent psychologist William James in his 1890 work *The Principles of Psychology*.
According to this theory, the perceived length of a given period of time (e.g., a year, a month) is relative and proportional to the total length of life that a person has already lived. This means that for a young child, each successive year represents a significant fraction of their life so far, which makes time seem to pass more slowly and be richer in experiences. For example, for a three-year-old, one year is as much as one-third of their life. As a person ages, that same year becomes an increasingly smaller fraction of their total lifetime. For a forty-year-old, a year is merely 2.5% of their life, and for an eighty-year-old, 1.25%. This decreasing proportion causes objectively constant time intervals to be subjectively perceived as increasingly shorter and passing more quickly. This mechanism is closely linked to the role of attention and novelty in perception. William James emphasized that perception is not a passive reception but an active process in which our attention (selectivity) determines what we choose from the “stream of consciousness.” In childhood, attention is constantly engaged by a multitude of new stimuli, which leads to a more intense encoding of memories and a subjective lengthening of time. In adulthood, faced with routine, the brain employs a mechanism to “filter out” familiar and repetitive stimuli from intensive processing, which contributes to the impression that time is passing more quickly.
An important note regarding authorship:
It is important to distinguish between two prominent French thinkers named Janet who were active during a similar period and whose works are sometimes confused:
- Paul Janet (1823–1899): Philosopher, author of the original concept of the theory of the proportionality of time (1877).
- Pierre Janet (1859–1947): Paul’s nephew, a distinguished psychologist and psychiatrist whose works (e.g., *L’Automatisme psychologique*, 1889) focused on psychological automatisms, the subconscious, and personality disintegration. His contribution to psychology is immense, but he is not the author of the theory of temporal proportionality.
Bibliography
[1] Janet, P. (1877). A Study of the Concept of Time.
[2] James, W. (1890). *The Principles of Psychology*. Henry Holt and Company.