The pressure of judgement is not the same as the work pressure of a stressful scenario. It's why public speaking and job interviews are among the most feared activities people go through, but people consider meetings boring and mundane.
The point is more that for a person with a given skill level, interviews can be stressful and make them perform below that skill level. I try to structure my interviews such that people get more comfortable and I don't ram their head into a metaphorical wall. I get all the same information, but without all those hard feelings.
A few questions for you. How old are you? Have you hired developers before? Truthfully, have you ever had to reverse a string under pressure at your current job.
The general reason why such a question is asked is because interviewers don't have an infinite amount of time and there's no point in considering any candidate who can't do this. It's a way to weed out ridiculously bad candidates so that you can focus more on good candidates.
More often than not the people that spout that kind of nonsense are twenty-something junior developers that read a bit of HN and have decided that they know better than everyone else about what makes a good programmer.
Why would you test if someone can reverse a string if you're hiring someone to maintain and build on some shitty web app?
Doing a string reverse is so trivial that it's not about needing that skill, but rather what not being able to do that speaks about the candidate's general aptitude and skill level.
If that question can't be answered then your opinion on someones skill level is irrelevant. Also, if you've got time, answer the questions in my first post:
"How old are you? Have you hired developers before? Truthfully, have you ever had to reverse a string under pressure at your current job."
The only way this question wouldn't be useful is if you had a good filter such that almost everyone who gets to that point would answer that question correctly. But apparently, this is not the case. There are people who fail such tests (despite apparently good paper qualifications and ability to talk BS). It's fairly important that you not let through such imposters.
And yes I've hired people and all of them have had to answer much more complex algorithmic questions to get the job and all of them turned out to be competent. And "have you ever had to" questions are ingenuous - interview settings are never going to be replicated exactly in a work setting, unless your job is to go around to be interviewed for different jobs. Good interview questions don't simulate work setting - they extract most critical work-relevant information about the candidate without wasting time.
So...I'm hiring someone that can reverse a string because this demonstrates that they can program real things that real people use?
"And yes I've hired people and all of them have had to answer much more complex algorithmic questions to get the job and all of them turned out to be competent."
Out of interest, what did this job entail? I assume that you quizzed them on their knowledge of basic algorithms because they are required to write them, right?
The difference between reversing a string and pulling data from a database are, literally, completely different tasks. The killer is that the latter is something that a candidate will do in a job.
You're more than welcome to ask those questions, and you're probably likely to weed out the lowest common denominator types. In my experience, they're a waste of time and the best possible interview you can give to a developer is a frank face-to-face discussion about programming, and then getting them to work on a test project for two hours from your own code base. If they can do that much they can program.
Why can't you do both? Seriously? Pulling data from a database is orders of magnitude harder to get right than reversing a string.
And this is where you misunderstand the purpose of these types of questions. Programming is a very dynamic field where you're likely be required to solve novel problems daily (not novel in the grand scheme of programming, but novel to you). You need the mental flexibility and fluidity to solve problems you haven't entirely encountered before. Testing specifically what you do at the job is the wrong approach. You need to test the required mental faculties to solve novel problems. Programming is not pulling data from a database, writing glue code, and shoving it to the screen. It's solving new problems every day.
Being able to recognise the correct answer in the sea of dross that is search engine results pages is better.
Being able to take the correct answer, and adapt it to what you need, and plugging it into what you already have, is best.
Do you really want to employ people who say they have X years of experience doing something but who cannot do a very simple task in the choice of their language? That's not a stupid trick gimmick question - there's no "gotcha" there. Perhaps we're getting caught up on the specific "reverse a string". Substitute that for something relevant to maintaining and building on a shitty web app.
To put it another way - when I code it's rarely different from writing to me; code is simply an expression of thought. But when you ask me to do something that seems a bit artificial (reverse a string) it's like asking me to write a haiku - I can do it, but give me a moment while I count out my syllables.
If so are these people who have held down a programming job before?
reversed_string = string[::-1]