In my case such “short term mistakes” are often caused by fatigue. It’s as if my brain enters some kind of energy saving mode and sanity checks are deemed not quite as necessary as some other things. In one case I somehow managed not to notice a contradiction in the idea that a cube has four sides and because of that I failed to solve a problem in a school mathematics competition (it must have been one of the problems, as I must have been really tired by then). It seems to me that sanity checks are analogous to redundancy and duplication of components in engineering. Therefore it is not surprising that when the mental energy is very low my brain may decide that these safety measures are not necessary (of course, they aren’t until they are).
In another case, another student asked me how to solve a particular exercise saying that he tried to use a certain lemma he thought might be useful but was unable to apply it. It was only after some time of trying to solve it myself I got the idea to check whether the statement of a lemma was correct (it wasn’t). It seems that in this energy saving mode I did not to think about what exactly was the best thing to check given the fact that he tried and failed to solve it, and instead tried to solve it myself without a single thought that lemma’s statement might be incorrect. In other words, my brain did not try to estimate conditional expectations of possible action to take given all the facts I had, it “calculated” only expectations for a general case, when lemmas printed in a textbook are usually stated correctly (in other words, I did not take all the information into account when deciding what should I do next). Even if it still wasn’t more likely, the idea about wrongness of lemma should have at least occurred to me (and it would have been easier to check on a toy example). Of course, this seems to be a “hybrid” mistake as it seems to be caused by both failure of a heuristic (to trust mathematics textbooks) in this particular case and a fatigue induced tendency to avoid things that require mental energy.
However, it seems to me that such short term fatigue induced mistakes are quite different from long term mistakes and quite different methods are usually required to correct them.
In my case such “short term mistakes” are often caused by fatigue. It’s as if my brain enters some kind of energy saving mode and sanity checks are deemed not quite as necessary as some other things. In one case I somehow managed not to notice a contradiction in the idea that a cube has four sides and because of that I failed to solve a problem in a school mathematics competition (it must have been one of the problems, as I must have been really tired by then). It seems to me that sanity checks are analogous to redundancy and duplication of components in engineering. Therefore it is not surprising that when the mental energy is very low my brain may decide that these safety measures are not necessary (of course, they aren’t until they are).
In another case, another student asked me how to solve a particular exercise saying that he tried to use a certain lemma he thought might be useful but was unable to apply it. It was only after some time of trying to solve it myself I got the idea to check whether the statement of a lemma was correct (it wasn’t). It seems that in this energy saving mode I did not to think about what exactly was the best thing to check given the fact that he tried and failed to solve it, and instead tried to solve it myself without a single thought that lemma’s statement might be incorrect. In other words, my brain did not try to estimate conditional expectations of possible action to take given all the facts I had, it “calculated” only expectations for a general case, when lemmas printed in a textbook are usually stated correctly (in other words, I did not take all the information into account when deciding what should I do next). Even if it still wasn’t more likely, the idea about wrongness of lemma should have at least occurred to me (and it would have been easier to check on a toy example). Of course, this seems to be a “hybrid” mistake as it seems to be caused by both failure of a heuristic (to trust mathematics textbooks) in this particular case and a fatigue induced tendency to avoid things that require mental energy.
However, it seems to me that such short term fatigue induced mistakes are quite different from long term mistakes and quite different methods are usually required to correct them.