Is perception of time completely subjective?

Question

I know that if you are into an interesting activity time seems to pass very quickly, whereas the opposite happens when you're bored, but that's not what I'm asking.

Imagine conducting an experiment with two individuals whose job is to pay attention to how fast seconds go by using a clock. It's almost certain that if both people pay rigorous attention to the clock then their perception of "1 second" is bound to be more or less the same and we'll accept this as a fact.

However, since the world around us, and how fast or slow it is changing, is only a product of each individual's perception, is it possible that the perception of seconds for individual A is completely different from that of individual B, but since individual B is a part of A's world, each is consistent for the other?

For example, imagine that A has in mind a specific "duration" for 1 second, but A's 1 second can be B's entire lifetime, if A's perception of seconds is extremely "slowed down". I'm aware that this example holds only with the assumption that somehow A could feel how B feels and perceives the world, but is it possible?

EDIT: this question can be asked about space too. What if each individual's perception of space is different but because everything in this world is a product of one's senses, his "experience" is consistent with that of other human beings. What if a line in my world is a parabola in yours? What if everything through "your eyes" makes completely no sense to me?

Answer 1

Let me interpret this scenario in its extreme form: we have two individuals who are, from a third-person perspective, very similar to each other, including in cognitive abilities. In particular, they tend to have equally many, and similar, thoughts in one second. As a result, there is no way that, as third-party observers, we will be able to figure out that one has a longer perceived duration of a second than the other. (Well, maybe we could somehow figure this out inspecting their brains directly -- but at least by asking them questions, etc., we would not figure it out.) And yet, unbeknownst to us (and them), their subjective experience of the duration of a second is completely different.

This scenario seems to be a nice, temporal variant of the inverted spectrum scenario, where the way I experience red is similar to the way you experience green, but we have learned to call the same objects in the world red so we never know that what it is like for us to experience these objects is completely different. There is much literature about whether this could be possible (and what the relevant sense of "possibility" is -- see, e.g., work by David Chalmers such as this paper). One could have a similar discussion about your case, at least as I interpret your case. I hadn't seen this variant before, I like it.

(EDIT: a similar answer applies to the case about space that was edited into the question later.)

Answer 2

I was just listening to Geoffrey West discuss his book 'Scale: The Universal Laws of Growth, Innovation, Sustainability, and the Pace of Life in Organisms, Cities, Economies, and Companies.', and the origins of lifespan and subjective experience of time in metabolic processes.

It was recently pointed out to me, that part of the reason time speeds up as we get older is the tendency to increasinglybdo things 'on automatic', the decrease in experiences of true novelty requiring our total attention. We can observe this effect easily and directly.

Total anaesthesia is experienced as no time having passed, whereas normal unconsciousness and sleep we usually have some sense of time elapsed. It is likely then a mental 'ticking' is involved as well as metabolic processes - although the brain and heart are linked in our assembly of our interioceptive picture so it may simply be that.

Subjective experience of time then seems to be linked to metabolic and mental processes - both conscious and unconscious.