I think that falling into the trap of treating social skills and technical ability as a trade-off is a mistake. It's a hackneyed stereotype that I don't think has ever been true--but I'd imagine it has sometimes led to people expressly trying to seem socially abnormal in order to fit the idea of someone technically adept. I recall an anecdote about how a younger mathematician at a top research institution took up running his hand along the wall as he went places in order to seem odder, since it seemed like the best senior mathematicians there all had odd quirks. I'd imagine that the idea that social skills and technical ability are inversely correlated has led to similar things.
But also, my experience in TAing the weed out course for the CS major (and from seeing my fellow TAs teach and work, who were more or less the best in class at my University--so much so that I was flown out by a company simply because of my involvement in that class) was that social skills had absolutely no correlation to technical ability: your ability to understand how pointers or complex data structures worked had absolutely no relation to how socially fluent you were. In fact, it often went the opposite way, up to a point: there was some base line of social fluency that everyone I worked with and the best people I taught seemed to meet. The single best coder I have /ever/ seen work (he alone makes me absolutely certain that the best people in our industry are 10x/100x more productive than the average) was also one of the most comfortable with people and had a very clear idea of his career goals. I'd expect him to give confident, unhesitating responses to "Where do you see yourself in 5 years?" and "What's your greatest strength/weakness?" Negatively weighting that would mean you'd miss the hands down most productive person I've ever seen work: and you'd probably miss a decent number of the other people I taught with. (Who, as I said, were basically the cream of the crop from the program I was in. Not all of the best people were there, but all of the people there were among the best.)
Now, I don't think they're particularly good interview questions, even though I understand why they're asked. I think that asking questions about actual workplace soft skills (conflict resolution, for instance) would be a much better use of everyone's time, since in the end it's those things that actually hold a team together.
It's less to do with social skills (agreed, there's no trade-off) and more to do with the probability that people scoring 6 out of 10 for their ability to discuss technical problems whilst getting 10 out of 10 for their ability to answer general interview questions are good interviewers with a weakness for understanding technical problems, whereas those scoring 6 out 10 for technical problems questions but 5 out of 10 for generic interview questions are likely underrepresenting their technical understanding due to the awkwardness of the interview situation. I'm also assuming that some common non-technical questions (like biggest weaknesses, and what they actually did in their last job) usually elicit useful information as opposed to answers synthesised from the job spec.
Since I've introduced arbitrary numerical scoring, I guess by "negatively weighting" I actually mean doing something equivalent to mutiplying their overall performance by 1 + scalefactor*(technical answers score - generic interview answers score) , but I'm assuming in practice most interviewers use their intuition rather than subjectively scoring every answer.
I'm assuming your amazingly productive friend aces the technical questions at least as impressively as the "convince me you'll have grown with the company after 5 years, even if you actually only see this as the bottom rung of the ladder" ones.
I think you miss the point. It's not that people with social skills are likely to be worse technically, it's that social skills help you even on the technical questions in a setting where you are basically trying to sell yourself and being judged socially. Weighting the purely-social questions negatively might serve as a control.
A reasonable theory; I'm skeptical as to whether it would turn into better performance in hired candidates.
I think that you're right about this. People with poor social skills are going to be worse at negotiating pay and in much lower demand, overall. On the other hand, I'd assert that they're going to be harder to manage and lead to more interpersonal issues (almost by definition).
But also, my experience in TAing the weed out course for the CS major (and from seeing my fellow TAs teach and work, who were more or less the best in class at my University--so much so that I was flown out by a company simply because of my involvement in that class) was that social skills had absolutely no correlation to technical ability: your ability to understand how pointers or complex data structures worked had absolutely no relation to how socially fluent you were. In fact, it often went the opposite way, up to a point: there was some base line of social fluency that everyone I worked with and the best people I taught seemed to meet. The single best coder I have /ever/ seen work (he alone makes me absolutely certain that the best people in our industry are 10x/100x more productive than the average) was also one of the most comfortable with people and had a very clear idea of his career goals. I'd expect him to give confident, unhesitating responses to "Where do you see yourself in 5 years?" and "What's your greatest strength/weakness?" Negatively weighting that would mean you'd miss the hands down most productive person I've ever seen work: and you'd probably miss a decent number of the other people I taught with. (Who, as I said, were basically the cream of the crop from the program I was in. Not all of the best people were there, but all of the people there were among the best.)
Now, I don't think they're particularly good interview questions, even though I understand why they're asked. I think that asking questions about actual workplace soft skills (conflict resolution, for instance) would be a much better use of everyone's time, since in the end it's those things that actually hold a team together.