How quickly time appears to pass depends on the “clock” against which change in the perceived world is compared. By a clock is meant a separate stream of change appearing simultaneously with the perceptions being timed. There are what I’ll term “objective clocks”, whichconsist of aperiodic motion with a nearly-constant period. These occur overa vast range of scale – the ticks of a clock, beats of a heart, length of a “day”, of a “week”, and of seasons, the extent of a lifetime. We develop a concept for the time intervals of these clocks through our repeated exposure to them. Against an objective clock, one can obtain an objective measurement of elapsed time – one whose scale is independent of subjective interpretation. When I say this, however, it must still be recalled that all time experience requires an entity with memory – to retain the perceptions of the clock “ticks” and the phenomenon being timed – and consciousness, so that a concept of time interval can form.
However, we also experience a more psychologically-based time measurement, which lacks the uniformity provided by a clock. Let me express this first through some examples.
Let’s start with “anxious waiting”. When we are waiting, time appears to pass very slowly. Waiting in a line, sitting through an uninteresting meeting or class, getting delayed while travelling, all of these cases can be catagorized as time dialation caused by anxious waiting. Time also appears dialated during emergencies, which would appear to be the complete opposite experience. However, I suggest that these two experiences – of anxious waiting, and of severe fearful excitement, have a common feature. When I am anxiously waiting, my mind wanders over a long list of items that I could – or should – be doing, instead of passivelyfacing the wait that I am currently compelled to experience. I consider with increasing emotional concern the impact of my lack of activity on meeting my day’s schedule, achieving my short term goals. My mind is occupied with a continual stream of various thoughts, andnegative emotions are engaged. In an emergency, I experience a similar mixture of heightened mental activity – in a desparate search for actions to relieve the emergency – combined with intense negative emotion. Under both of these circumstances, time is subjectively slowed.
Time passes quickly when our mind is focussed narrowly on a single stream of thought. If I spend an afternoon working on a single mathematics problem with no other distractions, the hours will pass by rapidly. The more narrow the field of consideration, the more rapidly time appears to pass. In the extreme, when we sleep peacefully, time passage appears instantaneous. Notably, if we sleep poorly, or are disturbed by dreams, negative emotion stirs, and we have a “long night”. Not to be trite, but time does indeed pass quickly when we are “having fun” – positive emotion, coupled with a narrow mental focus, or a lack of focus, speeds the subjective passage of time.
Attempting to generalize from these observations, I suggest that the subjective rate of time is a function of the level of mental activity. The more “mental states” we experience in a fixed interval of (objectively measured) time, the longer that interval appears to last. I further conjecture (based again on self observation) that the rate of change of mental state is in general higher when we areexperiencing negative emotion, than when we experience positive emotion. The link to our experience of time durationcan be explained if we are comparing the rate of change in our external world to the rate of change in our mental state – that is, if our mind’s actions are the “clock” against which we are measuring time.
I fully recognize that this hypothesis is very incomplete. Note that I have not defined “mental state”, nor can I explain the conjecture that rapid change of mental states generally give rise to negative emotion. I will next attempt to sketch – still realizing this is only a suggestive sketch – of what I mean by mental state.