When I was a kid, summer holidays (those two magical months of July and August) seemed like an eternity. Now however, as a 37 year old, it seems like it was just yesterday that I was launching fireworks to celebrate Labor day weekend (we really did. And it was amazing!). That was over 2 months ago. I’m sure most “adults” can relate to this feeling of time moving faster the older you get. But perhaps there’s a reasonable explanation for this effect.

Time is conventionally thought of in the continuous space. I’m sure quantum physicists much more intelligent than I have postulated on a discrete time domain, but for now, I perceive time as continuous. However, I have recently been implementing reinforcement learning algorithms in robotic domains, where time is discretized.

In such domains, the robot agent “wakes up” at certain frequencies for computation. At each instance the agent “wakes up”, the robot must choose an action, take the action, observe the environment, and finally learn.

In the robot environments I have worked with, I, the designer, have defined the learning rate. This rate defines how often the agent “wakes up” – where it observes it’s most recent environment, as well as takes an action.  To such an agent, it is easy to imagine that the only definition of “elapsed time” is the number of learning cycles it has processed. It has no concept of what happened, let alone how long it took, between these learning cycles.

It is natural to believe that a young child has a much more active brain, processing at a more frequent rate than an older senior. Imagine if a young child “learns” 1000 times per second, and a senior learns only 100 times. To the child, a year represents 10X more learning cycles, so quite literally feels 10 times as long. Similarly, there is an intuition on the perception of elapsed time (or lack there of) with people waking up from a nights sleep, or from a comatose state.

I am making huge generalizations when comparing the human brain to this simple agent / environment framework. I barely have a basic understanding of neurology. But I suspect that the brain doesn’t just operate on a single discrete observation set at certain frequencies. So this comparison to the simple RL environment is somewhat naive. However, at some level, one could imagine that the computational frequency of the human brain slows down with age. If that is the case, and if you believe that is the only metric we have to perceive the passage of time, it only seems natural that time does indeed speed up as we age.