Using "number of pawns of evaluation lost" as a proxy for the severity of the blunder has some fundamental problems. The main one is that the relationship between evaluation in "pawns" and expected result (expected value of the game result, from 0 to 1) is not linear. (It couldn't be, since one of them maxes out at one.) It's actually more of a sigmoid curve.
This means that a player may easily make a horrific "3-pawn blunder" reducing his evaluation from +8 to +5, but in fact all he's done is reduce his chance of winning from 99% to 98%. Actually, the +5 move may even be better in practice, in that it might lead to a sure safe win rather than a tricky blowout.
Even if you changed the definition of blunder from "reduces the evaluation by n pawns" to "reduces the expected result by x", I would have an issue in that it ignores any of the human aspects of blunders. If someone drops a pawn outright for no reason (eval change -1), that is a blunder because it was so trivial to avoid. But if someone, even a grandmaster, makes a move that causes a large drop in eval due to allowing a sacrifice that no human could calculate all the ramifications of, because as far as he (and probably his opponent) could humanly calculate it didn't lose, it is hard to call that a blunder. (Conversely, failing to see some immensely complicated non-forcing winning move may be unfortunate but it's not a blunder.) But that's more a cavil with terminology than a methodological error; the study is still measuring something interesting, just not quite what I think it is claiming to measure.
Somewhat agreed. I'm a decent-ish amateur player and if I'm playing bullet or blitz chess with very low time left on the clock (<10 seconds), and its king pawn vs king ending and I'm about to convert my pawn, I will almost always choose to under promote to a rook instead of promoting to a queen because I am 100% sure I can mechanically checkmate my opponent without accidentally stalemating (due to a blunder under extreme time pressure) while spending virtually no clock time. I could almost certainly do it with a queen, but it's for my own peace of mind that I use a rook instead. Safe and easy victory, but it'd count as a blunder.
Nope, "number of pawns" is only a notional number, it's a score calculated by a chess engine. Being 1 pawn ahead may just mean a particular position where one side has an equivalent advantage though not necessarily being a physical pawn ahead. Another aspect is sometimes you're a physical pawn short, but the position evaluation may only show -0.3 pawns against you, meaning you've got positional or counter-play advantages to compensate. Often players will sacrifice pieces for counter-play and activity.
Chess engines also implement a heuristic called 'contempt' where they may make a sacrifice in order to avoid a drawn position, when faced with an inferior opponent.
Your response has absolutely nothing to do with the point the parent poster makes and completely and utterly misses the point.
He is arguing that "percentage of winning" is not linearly related to "pawn or equivalent advantage". That has got nothing to do with whether those pawns are physical ones or positional advantages that have equivalent value.
Yes, I know how computer evaluations work. The fact that they take positional as well as material considerations into play doesn't change the point, which is that playing a +5 sure-win move instead of a +8 sure-win move is not a horrific magnitude-3 blunder the way that playing a -2 move instead of a +1 move is, whatever your units of magnitude are, because what really matters is the change in the expected result of the game.
Yup, this is another very valid criticism. I think the answer is probably to have a cutoff on the lower bound. Basically saying that for a move to be a blunder it has to leave below a certain absolute value, maybe +2 pawns, in addition to a certain amount below the best possible move.
This means that a player may easily make a horrific "3-pawn blunder" reducing his evaluation from +8 to +5, but in fact all he's done is reduce his chance of winning from 99% to 98%. Actually, the +5 move may even be better in practice, in that it might lead to a sure safe win rather than a tricky blowout.
Even if you changed the definition of blunder from "reduces the evaluation by n pawns" to "reduces the expected result by x", I would have an issue in that it ignores any of the human aspects of blunders. If someone drops a pawn outright for no reason (eval change -1), that is a blunder because it was so trivial to avoid. But if someone, even a grandmaster, makes a move that causes a large drop in eval due to allowing a sacrifice that no human could calculate all the ramifications of, because as far as he (and probably his opponent) could humanly calculate it didn't lose, it is hard to call that a blunder. (Conversely, failing to see some immensely complicated non-forcing winning move may be unfortunate but it's not a blunder.) But that's more a cavil with terminology than a methodological error; the study is still measuring something interesting, just not quite what I think it is claiming to measure.