The subjective feeling that time accelerates as the years pass is known as time compression. This experience is not a failure of the clock but a complex function of how the brain perceives, records, and retrieves duration. Time compression is a psychological effect where the perceived duration of a past interval (subjective time) is significantly shorter than the measured duration (objective time). Understanding this process requires separating the physical reality of the clock from the mind’s internal mechanisms for tracking time.
The Cognitive Mechanisms Behind Subjective Time
The perception of time relies on a distributed network of brain regions that act as an “internal clock.” This timing system involves a complex interplay between the basal ganglia, particularly the striatum, and the prefrontal cortex. The striatum is thought to contain a pacemaker-accumulator system, where the pacemaker emits neural pulses counted by the accumulator to estimate duration.
The speed of this internal pacemaker is influenced by the neurotransmitter dopamine. Higher levels of dopamine, associated with reward and excitement, increase the rate at which these neural pulses are generated. When the internal clock runs faster, the brain accumulates more pulses for a given duration, leading to the perception that time has passed more quickly. This neurobiological link explains why “time flies when you are having fun.”
How Novelty and Memory Density Shape Retrospective Time
The primary reason time seems to speed up with age relates to how memories are encoded, a concept known as the memory density model of retrospective time. When reflecting on a past period, the perceived duration is based on the quantity and richness of unique, memorable events recalled. The more novel and detailed the memories for a given period, the longer that period subjectively feels.
Childhood and young adulthood are packed with “firsts”—first day of school, first kiss, first time driving—which are highly novel and emotionally salient events. These events recruit dopamine circuits that flag them as worth learning, leading to dense encoding and a vivid collection of episodic memories. In retrospect, a year from childhood seems vast because it is filled with a high density of unique, well-remembered experiences.
As we age, life tends to become more routine, with repeated experiences like a daily commute. The brain is an efficiency machine that compresses repetitive information, ceasing to encode what it can reliably predict. Since fewer novel events are encoded, the memory folder for an adult year contains less unique content, causing the entire period to compress into a thinner, faster-feeling duration upon reflection.
The Impact of Attention and Emotional State on Present Time
While retrospective time is shaped by memory density, prospective time—how we experience duration in the moment—is largely controlled by attention. When we are deeply engaged in an activity, our attention is directed outward toward the task, diverting cognitive resources away from monitoring the internal clock. This lack of attention to time leads to an underestimation of the elapsed duration, causing time to appear to speed up, or “fly by.”
Conversely, when a person is bored, waiting, or anxious, their attention is often drawn inward to the passage of time itself. Focusing on the clock or the duration of the wait provides more “samples” of the internal clock’s output, leading to an overestimation of the elapsed time. This attentional focus creates the sensation of time dilation, where minutes can feel like an hour.
Intense emotional states, such as fear or high anxiety, also significantly alter time perception through physiological arousal. The release of hormones like adrenaline increases the rate of information processing in the brain. This heightened state causes the internal clock to run faster, accumulating more pulses and leading to the prospective perception that an event is lasting longer than it objectively is. Because the memory of the highly arousing event is so rich, it can feel subjectively longer later on as well.
Strategies for Altering Subjective Time Perception
Since time compression is linked to a reduction in novelty and an increase in routine, altering the perception of time relies on intentionally disrupting these patterns.
One effective strategy is to actively seek out new experiences, such as traveling to an unfamiliar location or learning a new complex skill. These novel events force the brain to engage in dense encoding, creating rich, unique memories that will subjectively lengthen the perceived duration of the period when recalled.
Breaking established routines is another method to combat the brain’s compression algorithm. Changing the route of a daily walk, trying a new restaurant, or rearranging furniture can introduce enough novelty to force the brain to pay attention and create distinct memory markers. The goal is to avoid the brain’s tendency to bundle repetitive days into a single, thin memory file.
Practicing mindfulness or focused attention is a strategy for slowing down prospective time. By intentionally grounding attention in the present moment—focusing on sensory details, breathing, or a single task—you prevent attention from being scattered. This deliberate, moment-to-moment engagement increases the cognitive “sampling” of the present, making the immediate experience feel fuller and more substantial.