The below are my interviewing principles aimed at intermediate-level people who conduct standalone job interviews.

The first interview I've ever conducted was at Palantir, 2.5 years ago (at the end of 2012). An interviewer dropped out and there were only the 15 of us in Europe at the time - so I had a whopping 10 minutes to prepare for an interview for a different role than mine. It was seemingly a disaster - the interviewee was several levels above me intellectually at the time and owned the interview. 140 interviews later, I don’t think that it was a disaster anymore (although naturally one of my weakest interviews). My goal was to find the truth about his technical abilities - and I accomplished just that. We hired him and now he’s one of the strongest execution people in the European business.

What follows is a set of interviewing principles which apply to all roles. The role-specific parts of interviewing are signal collection and the hiring decision and these are outside of the scope of this discussion.

Finding the Truth

My goal as an interviewer is to find the truth about the candidate's intellect and personality in various dimensions that are important to us and then judge whether they would thrive here: whether they would provide value to us and whether we would provide value to them. The first-chamber (naïve) understanding of interviewing would suggest that I have to find the truth based on what the candidate says and does - whereas the reality is closer to saying that I have to find the truth despite all of that.

An Exercise in Intellectual Honesty

I really enjoy interviewing, and there are two main reasons for that:

1. It is fascinating to explore humans: their intellects, personalities, strengths, and weaknesses - and it is even more fascinating to do this as effectively (that is, accurately and fast) as possible.
2. Interviewing is an enjoyable exercise in intellectual honesty.

Why is it an exercise in intellectual honesty? Because doing it effectively relies on a few non-intuitive and difficult principles. Let me explain next what I think are the crucial traits of a good interviewer.

1. Leveraging Your Judgement Machine

Your Judgement Machine is a black box subconsciously evaluating an incomprehensibly large input (your perceptions) and outputting ‘feelings’ (your intuition). Most people tend to focus on intuition which misleads you, called ‘emotional bias’: for example, a person's attractiveness generating positive or negative emotions is irrelevant to your decision making. But ultimately, emotions evolved as a useful tool in decision making, and as such, your intuition can also aid you in surfacing signal: for example, it could indicate that a certain area is dodgy and you want to drill into that; and it could indicate that this person is a particularly good fit but unclear yet how.

A weak interviewer is not aware of these emotions, and frequently uses irrelevant intuition (emotional bias) to form opinions, yielding suboptimal outcomes (flawed assessments). A strong interviewer is aware of their intuitions, understands in what they are rooted, and leverages the relevant ones to adapt their questioning and to form an opinion.

Your Judgement Machine is a core value of yours as a human, and it is important that you cultivate it over time: correct it when it produces biases (signal that is inconsistent with reality) and leverage it where it’s reliable. This requires introspection and intellectual honesty, and it's hard.

2. Perceptiveness and Inference

Unrelated emotional responses are misleading foundations for assessment. So what’s useful signal then?

This is probably the hardest part. I want to find the truth about someone’s intellect and personality. But direct questioning doesn’t reveal the truth: every answer is just a proxy for the person’s real character.

1. Regarding direct cultural questions, such as “Why are you interested in this company?”, frequently candidates (especially the weaker ones) perceive that it’s in their interest to appear differently than they are (that is, probably subconsciously, lie): say “the right things” and appear “better”. So how do I figure out the truth?
2. Regarding technical questions, what does their answer really tell me about their intellect, rather than their experience or familiarity with the particular problem?

This is the creative part - figuring out what qualifies as signal and what conclusions we can draw from them. Some indicators matter, some don’t, and they also tend to depend on contextual information such as the candidate’s background and experience. The indicators are also specific to the role you’re interviewing for. So instead of a comprehensive list, I’ll give you two examples from a technical interview.

Let’s say I’m interested in the candidate’s motivations.

1. If I ask “why are you interested in this company?” and they say “because I’d like to work on important problems and have a big impact”, what does that tell me? Almost nothing. One: it is useless to take fakeable answers at face value (it does tell me though that they are aware of this dimension of the work, but not that they really care). Two: this is a very hard question, and requires introspection and good synthesis to answer, which is normally not expected on the spot.
2. One route is to dig deeper into this answer to collect dots (“why do you think this project was important?”): a superficial candidate would have a superficial answer with no substance (“because it had a big impact”), whereas a thinking candidate actually believing what they say would have an elaborate answer (“because it affected X people in Y way, and it’s valuable because of Z”) (and conversely: a substantive and elaborate answer is very difficult to produce unless you believe in it).
3. An even better way is to infer the motivations from dots collected in other conversations. What were their previous projects? What about them made the candidate pick them? What are the things they liked/disliked in their previous jobs? We have to dig deeper and deeper until we get to the truth with high confidence.

Regarding a technical point, let’s say our candidate has successfully and quickly figured out the algorithm to solve a problem, but they are struggling to turn the algorithm into conceptually clean code. What does that really tell me? Are they a universally weak coder? Could they learn to code better had we hired them? This is where context really comes in. Is this a person with 10 years of industry experience? Then this is a red flag: they either don’t learn very well, or they have a mental limitation or block preventing them to get better at this crucial skill. Is this an intern candidate? Then they are not expected to be experienced with maintainable and conceptually clean code, but they should still be able to turn algorithms into code - will three months be enough for the candidate to learn it? Are they a new grad? Then we could give them a chance - but are their other strengths big enough to take the risk?

Notice that the key is that I’m not asking for a synthesis from them (“why”), which is difficult to build and could be wrongly built, but rather, I ask them for the dots (“what”). I then interpret these dots in the candidate’s context, and build my own synthesis.

The point is: don’t take signal at face value, but look for what you can actually infer. This is a complicated judgement call, and requires perceptiveness, creativity, and experience.

3. Pragmatism

Sometimes interviewers subconsciously make up an assessment based on irrelevant indicators (such as emotional bias), but then go ahead and find fitting arguments to justify them (alleviating the cognitive pain of unfounded opinions and not uniformly “good”/“bad” candidate profiles). This is an example of confirmation bias.

For example: “I really don’t think this candidate is a good fit for us: his code wasn’t that great, and he had some weird comments about his previous workplace."

It is easy to “trust” the interviewer’s judgement. But when one thinks about it, the argument given is completely useless:

• What does “not that great” code mean? Would you never accept this level of coding, or did you just bring it up to support your unfounded judgement?
• What does “weird comments” mean? Did it show a lack of thought? Did it express an asshole personality? Or was he just angry with his company for some legit reason?

To clarify: I’m not discarding human intuition - the interviewer’s judgement is highly valuable. However, it is so easy to make unfounded judgements that it is always worth understanding the actual reasons for it.

Some tell-tale signs of unfounded opinions:

• Would the same signal be OK in another candidate? Is it justified that it’s not accepted here?
• Is the explanation too vague?

Digging into these arguments can reveal whether they are actually founded in relevant indicators or not.

Hence, it is important (and hard) to be pragmatic, and to judge candidates consistently based on real and believable reasons.

4. Assertiveness

I've just spent 45 minutes talking with a candidate, and now I have to decide whether to spend hundreds of thousands of dollars on them, invest my colleagues’ precious time to train them, take the risk of underperformance, and above all, have them be part of and thus influence our culture. The responsibility is big, but I have to form an opinion and present it to my colleagues.

At this point, it is easy to be indecisive. But in practice, it’s just a symptom of one or more of the following:

• The interview method is flawed and it doesn’t surface enough signal to make a decision.
• There is enough signal, but the interviewer didn’t think their arguments and decision through.
• The interviewer is uncertain about their own assessment ability and doesn’t trust their own judgement.
• The interviewer is afraid of the responsibility of committing to an opinion and taking the risk of making a hire.
• The interviewer is afraid to disagree with their colleagues.

A weak interviewer would deny these malfunctions and would succumb to indecisiveness. A strong interviewer would become aware of them and fix the root causes. This, again, requires introspection and intellectual honesty, and so it’s hard.

Conclusion

To sum up, in my current understanding, interviewing is largely an exercise in intellectual honesty, with four particular points:

1. Leveraging your Judgement Machine: avoiding emotional bias and using your intuition where it’s valuable
2. Perceptiveness and inference: paying attention to the right thing and drawing the right conclusions
3. Pragmatism: avoiding confirmation bias and making sure that subjective indicators stay consistent
4. Assertiveness: committing to a decision

These are generic to all interviews. The domain-specific points come in at two points:

1. the perceptiveness and inference part: what are the relevant indicators for this role;
2. the call to hire or reject: making the judgement call based on the input.

Both of these points are topics for future posts.

Some say that interviewing is so intuition-based and biased that it’s almost random and useless. I disagree: like many difficult decisions, hiring decisions also have both subjective and objective parts, but that doesn’t refute their purpose. Among other things, you can always work on the above four points to get better and better decisions.

Many thanks to FH, SC, EF, CBH, and TP for their input.