Just a data point, but I felt a need to write it:

I found here a link to an interesting article "Multitaskers bad at multitasking". According to the article, people who 'routinely consumed multiple media such as internet, television and mobile phones' were worse at three attention-related experiments described in the article. However these people have self-reported as better in multitasking.

Now here are some selected comments from below the article: (three comments from three different people)

Women make better multitaskers then most men, only because their lives depend on multitasking at home and at work...it seems the above study was just computer based, which is probably why the multitaskers didn't do so well...they were thinking of other things that they should've or could've been doing.

This is surprising. I'm fantastic at it. Perhaps the pool didn't actually include those who are actually gifted enough to multitask.

I am a multitasker. I have a conference call on mute as I type this. The advantage? Ignoring the detail allows me to focus on the big picture, ensuring my team are always realigning with the strategic objectives. I have a very competent group of focussed people. They're great with detailed tasks that require focus. They wouldn't let me near those activities as we all know I'd make mistakes. As a team we understand each other's strengths and weaknesses and it works well.

There is something valuable in these comments. First, some aspects of the work (such as focusing on the big picture) in a given context may be more valuable than what was tested in the experiment. Second, despite multitasker getting less utility per task, they may get more total utility, which would make multitasking a good strategy. Third, people are different, so even if the results of this experiment are relevant for majority of people, there may be some exceptions for whom multitasking is a way to get high quality work done.

However all three comments have somehow missed the essence of the article. If the article says "it was experimentally shown that people who believe to be good at multitasking work are statistically worse at work" you can't respond just by "that's nonsense, because I believe I am good at multitasking my work", unless you include some convincing evidence why we should believe that your belief is more reliable than similar beliefs of the other people who were experimentally proven wrong. (How about considering a possibility that you might be wrong, both about "being fantastic" and "focusing on the big picture"?) And that evidence should be something better than a cached thought (women being better multitaskers), or an ad-hoc excuse (a computer-based study can't measure the real multitasking).

I think we are already doing good about it on LW. I did not notice the gradual change in my epistemic hygiene expectations, until I read a text containing basic mistakes, which I probably would not have recognized as mistakes a few month ago. As an analogy, washing one's hands may feel like a boring ritual, until one sees other people eating with dirty hands and suddenly feels disgusted.