I don't mean just asking. Obviously, you can't know if you are disqualified because of that specific question.
But if the company (or the interviewer) puts too much weight on that question, treats it as a key point (raises a red flag if the prospect doesn't do it) they will lose on the long term.
Put it this way: If you relay on your employees free time to train themselves, you aren't in control of what they learn. If you don't relay on their free time to train themselves because you want to be in control, why is this question important?
I think it would be very useful to use that question the other way around. Like a... green flag?. It can "add points" for a good prospect.
I see what you mean.
If a company is expecting people to do their training based on side projects on their personal time, they are crazy. And that would be a red flag on the company. That's a big no-no.
For me, asking about side projects is more of giving a chance for the candidate to shine. I mentioned it on another comment, people tend to be more talkative and knowledgeable about things that they are passionate about. In that sense, they could get brownie points by talking about one.
Also side projects are not only for training (because not all of them are related to coding/work), as Daniel mentions on his tweet, those projects (development, craft, hobby) build up character, and teach lessons that cannot be learned in a classroom... things that can normally be seen on how people talk about them.
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