Competency and Culture
"Not a Culture Fit" Is the Most Expensive Sentence in Hiring
Researchers filmed 30 hours of real job interviews. "Not a fit" often meant "not like the interviewer." How to hire for culture add instead.
About This Series
This is the fourth post in our seven-part Competency and Culture series. So far we have looked inside the company: how ratings drift, how toxic high performers survive, and how values become measurable once they are written as behaviour. This post moves to the front door. The same vague judgements that distort reviews also distort hiring, and the most common one has a name everyone recognises: "not a culture fit." Get this right, and the people you hire will strengthen your culture instead of copying it.
In 2025, researchers published their analysis of more than 30 hours of video-recorded job interviews at a London recruitment agency. Their conclusion was uncomfortable: "suitable candidates may be dismissed as not a good cultural fit" because of the recruiter's or hiring manager's subjectivity, not the candidate's ability.
Every founder has heard the sentence. Many have said it. "Strong candidate, but not a culture fit." It sounds like a thoughtful judgement. It is often a feeling that the candidate is not quite like us, dressed up as a decision.
In a 20-person startup, that feeling does little harm. Everyone knows everyone, and the team is small enough to argue about it. At 80 or 200 people, it becomes a hiring filter. And a filter that selects for familiarity will, over time, give you a company full of people who think the same way, notice the same things, and miss the same risks.
What do interviewers actually mean when they say "not a fit"?
The London study, by Nilma Bonelli and Hua Zhu, was published in the journal World Englishes in 2025. Over three months, the researchers recorded real interviews at two branches of a major recruitment agency: 30 candidates, 9 recruiters, and more than 30 hours of video. The roles were ordinary office jobs: managers, accountants, IT professionals, sales representatives.
What they found was that "cultural fit" worked as a gatekeeper that nobody had defined. Candidates had to match the recruiter's preferred conversational style: how formal to be, how much to say, when to show enthusiasm. Those who did were seen as a good fit. Those who did not could be dismissed, even when they were suitable for the job. The researchers also made a point founders should take seriously: the outcome of an interview is shared between the candidate and the interviewer, not decided by the candidate alone.
This is not a new finding, but it keeps being confirmed. A widely cited 2012 study by sociologist Lauren Rivera, based on 120 interviews with hiring evaluators at elite banks, law firms, and consultancies, found that more than half ranked cultural fit as the most important criterion at interview stage. And by fit, they largely meant similarity: in background, hobbies, and the way people presented themselves.
Put simply, when "fit" is not defined, interviewers define it as "like me."
Why does fit turn into sameness as a company grows?
In the early days, fit is real and useful. A founding team needs people who can move fast with little structure, tolerate ambiguity, and care about the same problem. Hiring for that is sensible.
The trouble starts when the early team becomes the template. Every new hire is compared, often without anyone saying so, to the people already there. Candidates who talk, think, and work like the founding team feel like a fit. Candidates who bring something different feel like a risk. Each individual decision seems reasonable. Added together over a few hundred hires, they produce a company that is very good at the things it was already good at, and blind to everything else.
A helpful way to see why this happens is the Iceberg Model of competence, set out by Lyle and Signe Spencer in Competence at Work (1993). Above the waterline sit the visible things: knowledge and skills. Below it sit the things that actually drive long-term performance: motives, values, and how someone sees themselves. "Fit" judgements tend to react to surface signals, like accent, school, hobbies, or conversational style, because those are what an interviewer notices in 45 minutes. The things that matter most sit below the waterline, where a gut feeling cannot reach.
What this looks like in practice
look at your last ten "not a fit" rejections. For each one, write down the specific value and the specific behaviour that was missing. If you cannot, the rejection was about familiarity, not culture.
Why do some people struggle in one company and thrive in the next?
We have seen the same pattern in almost every company we have worked in. Someone is labelled "not a fit," leaves, and becomes a standout somewhere else. Here is one example.
From our experience
A product manager at a Series B company was rated "not a culture fit" in their first year. They asked a lot of questions in planning meetings and pushed back on roadmap decisions. In a team that valued speed and agreement, that read as friction. They left after 14 months.
At their next company, a team that valued debate before commitment, the same habits made them the person leadership relied on to stress-test big bets. Within two years they were leading the function.
Nothing about the person changed. The definition of "fit" did.
The first company did not lose a bad hire. It lost the one person who was asking the questions nobody else was asking, and it lost them because "fit" had quietly come to mean "agrees quickly." That is the real cost of the sentence. You rarely see it, because the people you filter out go on to succeed somewhere you are not looking.
There is a second cost, which is what the label does to the people who stay. When everyone sees that the person who pushed back was managed out for not fitting, they learn the rule. Fewer questions get asked. Risks get raised later. The team looks more aligned and becomes less safe.
What this looks like in practice
when a manager says someone is "not a fit," ask one follow-up question: "Which of our values are they not living, and what did you see them do?" If the answer is about style rather than behaviour, you are about to lose someone for being different, not for being wrong.
What is culture add, and how is it different from "anything goes"?
Culture add asks a different question. Not "will this person fit in with us?" but "what will this person add to how we work?" A candidate who brings a perspective, skill, or working style your team is missing is not a risk to your culture. They may be exactly what it needs next.
This is where founders sometimes push back, and fairly. Culture add does not mean anything goes. You still need people who share your core values. Someone who does not care about customers is not a culture add at a customer-obsessed company, however interesting their background.
The distinction is simple once you see it:
| Culture fit (as usually practised) | Culture add | |
|---|---|---|
| The question | Are they like us? | What do they add, while sharing our values? |
| What gets tested | Style, background, conversational ease | Values, written as observable behaviour |
| What it rewards | Familiarity | Contribution |
| What it filters out | People who are different | People who do not share the values |
| Long-term effect | A team that thinks alike | A team that sees more |
The line between the two is the line our previous post drew. If your values are written as behaviour, you can test for them directly and stay open on everything else. If your values are just words, "fit" fills the gap with familiarity.
How do you interview for culture add without lowering the bar?
You do it by making the culture part of the interview as structured as the skills part. Four changes make most of the difference.
- Retire "fit" as a verdict. No candidate is rejected on culture grounds without naming the specific value and the specific behaviour that was missing.
- Test values as behaviours. Ask for real examples: "Tell us about a time you disagreed with a decision after it was made. What did you do?" Score the answer against your written behaviour descriptions, not against how comfortable the conversation felt.
- Ask what they would add. Give every interviewer one question to answer in their feedback: "What would this person bring that our team does not have today?" It changes what interviewers listen for.
- Separate style from substance. Train interviewers to notice when they are reacting to how someone speaks rather than what they say. The London study shows how easily conversational style becomes a stand-in for ability.
None of this lowers the bar. In The Best Hire You'll Ever Make Is Not on Any Job Board, we made the case for role-specific scorecards and structured assignments over gut feel. Culture add applies the same discipline to values. It moves the bar to the things that matter: skills above the waterline, values below it, both tested with evidence.
What this looks like in practice
add one line to your interview scorecard: "What would this person add?" Make it mandatory. Within a quarter, you will notice which interviewers are hiring for familiarity.
How does this connect to the rest of the series?
"Culture fit" is the hiring version of the same problem we have followed through this series: a vague judgement doing the work that a clear description should do.
It connects to our first post, because the interviewer is a rater like any other. Most of an interview judgement can reflect the interviewer, just as most of a performance rating can reflect the manager.
It connects to our third post, because values written as behaviour are what make culture add possible. Without them, "fit" is the only culture test an interviewer has.
And it connects forward. The people you hire for what they add will only stay if your review and pay conversations reward that contribution. In our next post, we look at why the conversation about pay and the conversation about growth should never happen in the same meeting.
The reframe underneath all of it is simple. Culture is not a mould that new people are pressed into. It is what your people do every day, and the right hire changes it for the better. Hire for your values, test them as behaviour, and let everything else be different.
Frequently asked questions
- What is the difference between culture fit and culture add?
- Culture fit asks whether someone is like the people already here; culture add asks whether they strengthen the culture you are trying to build. Fit tends to reward sameness, while add rewards people who share your standards but bring something the team is missing.
- Why is "not a culture fit" a warning sign?
- Because it is often subjective bias dressed as judgement. A 2025 study of more than 30 hours of recorded interviews found that suitable candidates were dismissed as not a good cultural fit because of the interviewer's subjectivity, not the candidate's ability.
- How do you interview for culture add without lowering the bar?
- Define the behaviours and standards that matter, then assess against those explicitly rather than against a gut feeling of similarity. You keep the bar high on how someone works while staying open to people whose background, style or perspective differs from the incumbents.
