Which of these two would you go for if you had to choose?
Scenario 1: You will experience severe pain, of constant intensity J, for an hour later today. You will live for at least the next 40 years.
Scenario 2: You will experience severe pain, of intensity J, for about a quarter second every day for the next 40 years, which will add up to an hour.
Keep all other things equal: in neither case will you get PTSD; in neither case will the pain come at an inconvenient time that would cause you to crash a car; etc.
Scenario 2 is appealing--a quarter of a second of pain experience does not seem so bad. You notice it, and then it's over. But knowing that every day you will face that pain again could wear one down. So it's not clear whether Scenario 1 or Scenario 2 is the wiser choice. But now consider the following scenario that fixes the problems with Scenario 2:
Scenario 3: You will experience severe pain, of intensity J, for about a quarter second every day for the next 40 years, which will add up to an hour. Moreover, you will not remember that you took up this offer, and immediately after you've experienced the pain for a quarter second, you will completely forget about it.
Scenario 3 doesn't have the disadvantages of Scenario 2. The mere raw experiencing of a quarter second of intense pain does not seem very bad, not even if repeated daily. I think Scenario 3 is significantly preferable to Scenario 1.
But now suppose Jones does not anticipate future pain or remember past pain. Scenario 1 for Jones is just like Scenario 3 for you. In Scenario 1, the quarter second pain experiences are all bunched up in a big nasty hour-long period, but that bunching up makes no subjective difference for Jones without relevant memories and anticipations. Since Scenario 1 for you is significantly worse than Scenario 3 for you, it follows that Scenario 1 for you is significantly worse than Scenario 1 for Jones.
This thought experiment suggests that a good deal of the badness of our pain comes from memory and anticipation.
I've wondered before whether pain for animals that lack our cognitive sophistication is worse or less bad than it is for us. A reason to think it's worse for them is that they don't have the intellectual resources for distracting themselves from the pain (e.g., by means of memories of or hopes for a happier past). But the above thought experiment strongly suggests that for animals and people with very low cognitive sophistication, pain is significantly less bad than for normal humans.
I wonder how exactly the badness of pain depends on cognitive sophistication.