In 2012, Google launched an internal research project called Project Aristotle. The goal was to find out what made some teams significantly more effective than others. They studied 180 teams over two years, looking at everything: individual IQ, personality types, seniority, gender mix, how often people socialised outside work.
None of it predicted team performance.
What did predict it was one thing: whether team members felt safe to take interpersonal risks. To speak up, disagree, ask a question that might seem stupid, admit a mistake without fear of embarrassment or punishment.
Google called it psychological safety. The concept itself came from researcher Amy Edmondson at Harvard Business School. But it took Google's data to bring it into mainstream leadership conversation.
What psychological safety actually is
Psychological safety is not the same as comfort. It is not about making sure everyone feels good, avoiding conflict, or creating a culture where nothing difficult is ever said.
Edmondson's definition is precise: psychological safety is a shared belief that the team is safe for interpersonal risk-taking. It is not about physical safety or job security. It is about whether people believe that speaking up will be met with curiosity rather than punishment.
A team with high psychological safety is not a team without tension. It is a team where the tension gets named instead of managed around. Where someone can say "I think we are making a mistake" without calculating the political cost first.
Why it is missing in most fast-growing teams
Psychological safety does not disappear because leaders are bad people. It disappears because the conditions that create it are systematically undermined by the conditions that create fast growth.
Speed. In a team that is moving fast, there is no time for the long conversation. The person who had a concern did not get the space to raise it. They learn, over time, that the space will not be created. They stop trying.
Success. A team that is winning does not question its own methods. If the numbers are green, the assumption is that what is being done is working. The things that are not working go unnamed because naming them feels like undermining something that is succeeding.
The leader's behaviour. Psychological safety is set by the person at the top of the room. Not by what they say about openness and feedback. By what they do when someone actually says something difficult. If the leader responds to challenge with defensiveness or dismissiveness, the message is clear. People learn what is and is not safe to say.
This is the part that is hardest to see from the inside. Leaders almost always believe their teams feel safe to speak up. Their teams almost always do not.
How to recognise whether your team has it
In meetings, do the same people always speak first? If so, the others have learned that the space is not reliably theirs.
When something goes wrong, what happens? Is the conversation about what can be learned, or about who is responsible?
Does anyone ever say "I don't know"? In a team with low psychological safety, admitting uncertainty is too risky. People perform confidence they do not have.
Do people ever push back on the founder or CEO in a meeting? Not in private, afterwards. In the room, in the moment. If the answer is never, that is worth examining.
Do you ever hear about concerns through a third party, after the fact? If concerns travel sideways before they come to you, the team does not believe the direct route is safe.
What to do about it
Psychological safety is built slowly and destroyed quickly. One moment of visible irritation when someone challenges you can undo months of stated openness.
The most important thing a leader can do is to demonstrate, repeatedly and consistently, that speaking up is met with genuine curiosity. Not performative thanks. Actual engagement with what was said.
That means asking questions before giving answers. Saying "I don't know" when you don't know. Changing your mind in a meeting when someone makes a good argument, and saying explicitly that you changed your mind because of what they said.
It also means naming the dynamic when it is absent. If a meeting ends and the people who usually go quiet were quiet again, say something. Not in a way that puts anyone on the spot. In a way that acknowledges: there is something in this room that is making it hard to say certain things, and I want to understand what it is.
That conversation is the beginning of something. It is also one of the hardest conversations for a founder to start. Because starting it requires admitting that the culture you have built may not be the culture you thought you had built.
Mees Loman is the founder of Loman Leadership, a leadership coaching practice for founders and leadership teams of fast-growing companies in Amsterdam and beyond. lomanleadership.com