Interviewing while biased

Interviewing usually involves some level of subjectivity. I once struggled to decide about a candidate, and after some period of reflection, the only cause I can see is that I was biased against the candidate. That wasn't a happy realisation, but even so, it's one I think worth sharing.

Over my years, I've interviewed hundreds of candidates for software engineering jobs (I reckon somewhere in the 500-1000 mark). I've interviewed for many companies, for teams I was managing, for teams I worked in, and for other teams at the same company. In most places, I've been free to set the majority of the interview. I have a standard pattern, with a standard technical question, to which I have heard a lot of answers. The quality of the answers fall into one of three categories:

• About 40% give excellent, quick, effortless answers. These candidates pass the technical portion.
• About 50% are confused and make nearly no progress even with lots of hints. These candidates fail.
• About 10% struggle a bit but get to the answer.

Candidates in the final bucket are by far the hardest to make a decision on. Not answering a question effortlessly doesn't mean you aren't a good candidate - it might mean it's not something you are used to, you got interview nerves or a million other factors that go into someone's performance. It makes the process far more subjective.

Many years ago, I interviewed one candidate over the phone. It was their first interview with the company, so I had to decide whether we should take the step of transporting them to the office for an in-person interview, which has some level of cost associated with it. Arranging an in-person interview would also mean holding a job open for them, which would mean pausing further recruitment. The candidate had a fairly strong accent, but a perfect grasp of English. Their performance fell squarely into the final bucket.

For all candidates, I make a decision, and write down a paragraph or so explaining how they performed. My initial decision was to not go any further in interviewing the candidate. But after writing down the paragraph, I found it hard to justify my decision. I'd written other paragraphs that weren't too dissimilar, but had a decision to continue onwards. I wondered about changing my decision, but felt rather hesitant - I had a sneaking suspicion that this candidate "just wouldn't work out". Had I spotted something subtle I had forgotten to write down? Had their answers about their motivation given me a subconscious red-flag? I didn't know, but for the first time I can remember, decided to wait on sending my internal interview report overnight.

One day later, I still had a feeling of unease. But still didn't have anything to pin it on. In the absence of a reason to reject them, I decided the only fair thing to do was get them onsite for further interviews. Their onsite interviews went fine, I went on to hire them, they worked for me for over a year, and were a model employee. If I saw red-flags, they were false-flags, but more likely, I saw nothing.

However, I still wonder what caused me to decide "no" initially. Unfortunately, the only thing I can hypothesise is that their accent was the cause. I had previously worked alongside someone with a similar accent, who turned out to be thoroughly incompetent. I seem to have projected some aspects of that behaviour onto an entirely unrelated candidate. That's a pretty depressing realisation to make.

To try and reduce the chance of this situation repeating, I now write down the interview description first, and then the decision last. I also remember this story, and how my biases nearly caused me to screw up someone's career.