[hypertele-Xii]

This is because information in your brain is constrained by physics. It takes tangible time for signals to travel between neurons. When you're young, you're small, and the distances are shorter. As you age, you grow in size, and the signal length grows also. Thus as you grow you literally think slower; though hopefully, more effectively (wisdom). Your perception of time changes accordingly.

[breck]

By age 2 your brain is ~80% of its final adult size, IIRC. So not sure if this idea is correct (but at the very least plausible and intriguing!).

I think the experience of time has something to do with focus. When you are young, or on lsd, your brain doesn't filter out all the signals and so time "slows down" as you suddenly need to process more. I know this is a well researched idea, just forget the actual terms for it.

[nobody9999]

I'd say that subjective passage of time is more related to the amount of time you've lived.

When a year is 10% of your total lifetime, it seems a lot longer than when it's 2% of your lifetime.

[Retric]

I always took it as the number of new experiences you’re having. A work week might feel slower than a vacation week in the moment, but vacations tend to be more memorable. It’s shocking how much stuff you can pack into a few memorable days while months blur together.

[matthewdgreen]

There is research that shows that subjective passage of time depends on physiological changes to the brain. The most compelling example is that certain brain tumors make the passage of time seem extremely fast or slow to patients with them. The fact that time “seems to go faster” as you age is related to a normal aging related change (though natural, not caused by tumors.)

[layoutIfNeeded]

What you wrote has no basis in reality whatsoever. In fact, nerve conduction is slower in children than adults due to underdeveloped myelination.

[whatshisface]

Furthermore, "constrained by physics" would imply the speed of light, which is so much faster than nerve conduction...

[hypertele-Xii]

There are other constraints in physics than the speed of light.

[strbean]

My flippant guess would be that time perception changing with age would be related to the NMDA receptor. NMDA receptor function decreases with age[0]. My personal anecdotal experience with NMDAR antagonists is that it feels like the `Turbo` mode on old IBM compatibles[1] -- i.e. downclocking. And the slower you process, the faster the world seems to move around you.

[0]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3181613/

[1]: https://en.wikipedia.org/wiki/Turbo_button

[User23]

My even more flippant guess would be that adults drink more alcohol than children.

[shadowofneptune]

From what I remember from development 101, there are also more possible synaptic connections in early childhood, and these get pruned down over time. This would also reduce the amount signals travel.

[bigphishy]

Yes that's an interesting aspect that I hadn't thought of. I do agree with the wisdom part. ;)

I also like to consider the experience of time in relation to total life lived.

e.g. A month to a five year-old is the equivalent of a year to a 60 year-old.

So as we experience more time, we feel that time passes more quickly. Although I sure hope there is a plateau to it as we get older.

[frongpik]

Not exactly a plateau. More like a singularity threshold.

[Sargos]

You stop growing physically bigger after around 20 years so this doesn't make any sense.

[User23]

Action potentials travel significantly faster in adult human brains than in children because for the latter the myelin sheath isn't yet formed.

[frongpik]

That's my perception as well, but iirc, time was slow for me when I was 25. I'd attribute this acceleration to neurons wearing out and thus needing more time to conduct signals, as well as growing apathy when there's less "wow" moments in life and more of "I've seen this before". Adrenaline allows to temporarily restore the proper pace of time.

[barkingcat]

What if the information in the universe is constrained by yet -unknown physics?

[_jal]

My favorite version of this is A Fire Upon the Deep, by Vernor Vinge.