I think you raise an important point: people legitimately have different opinions on what the scale should mean, and there might also be cultural factors that skew how people perceive they should respond on aggregate. If there is such a thing as a true hedonic scale for how people actually feel about their life that can be compared from person to person, survey data isn’t an ideal proxy for it.
But I don’t think the average person responding assumes the valence symmetry that you probably assume. Most people do want to go on living and so it’s not unreasonable to assume that the bottom half of the scale which goes all the way up to the “best possible life” isn’t supposed to represent different degrees of unbearable torture. I imagine most of the large fraction of the world’s population who awarded themselves a 4⁄10 on that scale would be utterly horrified by the idea that this might imply their life wasn’t worth living.
I think you raise an important point: people legitimately have different opinions on what the scale should mean, and there might also be cultural factors that skew how people perceive they should respond on aggregate. If there is such a thing as a true hedonic scale for how people actually feel about their life that can be compared from person to person, survey data isn’t an ideal proxy for it.
But I don’t think the average person responding assumes the valence symmetry that you probably assume. Most people do want to go on living and so it’s not unreasonable to assume that the bottom half of the scale which goes all the way up to the “best possible life” isn’t supposed to represent different degrees of unbearable torture. I imagine most of the large fraction of the world’s population who awarded themselves a 4⁄10 on that scale would be utterly horrified by the idea that this might imply their life wasn’t worth living.