In 2012, Google launched Project Aristotle — an internal research initiative to understand what made its most effective teams effective. The research team analysed 180 teams, reviewing reams of performance data and interviewing hundreds of employees. They expected to find that the best teams had the best individual members — the smartest, most experienced, most technically capable people.
What they found was different. The single strongest predictor of team effectiveness was not individual capability but psychological safety: whether team members felt safe to speak up, ask questions, admit mistakes, and take interpersonal risks without fear of embarrassment or retribution.
Amy Edmondson of Harvard Business School, who coined the term "psychological safety" in 1999, had anticipated this finding. Her research across hospitals, manufacturing plants, and technology companies consistently found the same pattern: teams with high psychological safety learn faster, adapt better, and perform at a higher level — particularly in complex, uncertain, rapidly-changing environments.
What Is Psychological Safety?
Psychological safety is the shared belief within a team that it is safe to take interpersonal risks — to speak up with ideas, questions, concerns, or mistakes without fear of being punished, embarrassed, or marginalised.
It is important to understand what psychological safety is not. It is not:
Niceness. Psychologically safe teams are not necessarily nice or conflict-free. They can have robust, challenging debates. The difference is that disagreement is engaged with, not punished.
Comfort. Psychological safety is not the absence of challenge or pressure. It is the presence of the conditions that allow people to meet challenge effectively — by asking for help, sharing concerns, and admitting when they don't know.
Agreement. Psychological safe teams are not echo chambers where everyone agrees. In fact, the research shows that psychologically safe teams are more likely to surface dissent and debate — which is exactly what produces better decisions.
Edmondson defines psychological safety precisely as: "a belief that one will not be punished or humiliated for speaking up with ideas, questions, concerns, or mistakes."
Why Psychological Safety Matters
The evidence for the importance of psychological safety is extensive and consistent.
Team performance. Teams with high psychological safety outperform low psychological safety teams across virtually every performance metric: creativity, decision quality, learning speed, customer satisfaction, and financial outcomes (Edmondson, 1999; Frazier et al., 2017).
Error prevention and learning. In hospitals, Edmondson found that teams with high psychological safety reported more medication errors — not because they made more mistakes, but because they felt safe reporting them. And teams that reported more errors learned faster and had better patient outcomes. Psychological safety doesn't eliminate mistakes; it prevents them from being hidden.
Innovation. Psychological safety is the foundation of innovation. New ideas are fragile — they require the safety to be shared before they are fully formed, to be criticised without being destroyed, and to fail without punishment.
Change adoption. Research consistently shows that psychological safety is the most important factor in successful organisational change. When people don't feel safe expressing concerns about change, those concerns go underground — and derail implementations from below.
Employee wellbeing. Teams with high psychological safety have lower rates of stress, burnout, and voluntary turnover. People can bring their whole selves to work when they don't have to manage constant self-protection.
What Destroys Psychological Safety
Understanding what damages psychological safety is as important as understanding how to build it. The most common destroyers are:
Public shaming or humiliation. When a leader responds to a mistake or a question with sarcasm, anger, or public criticism, it sends a signal to the entire team: this is what happens when you put yourself out there. The whole team adjusts their behaviour accordingly.
Ignoring or dismissing input. When people share ideas or concerns and are ignored or dismissed, they quickly learn that speaking up has no value. Voice decreases and silence increases.
Shooting the messenger. When raising a concern is met with defensiveness or blame, people stop raising concerns — and problems that could be addressed early become crises.
Excluding people from decisions that affect them. When team members have no influence over decisions that affect their work, they disengage — and disengagement destroys the psychological safety necessary for candid communication.
How to Build Psychological Safety in Your Team
The research identifies specific, evidence-based practices that build psychological safety.
Model vulnerability first
The most powerful thing a leader can do to build psychological safety is to go first — to model the vulnerability they want to see. This means: admitting uncertainty ("I don't know"), acknowledging mistakes ("I got that wrong"), asking questions ("Help me understand your concern"), and inviting challenge ("What am I missing?").
When leaders model vulnerability, it gives explicit permission for the team to do the same. Research shows that a single act of genuine vulnerability from a credible leader can significantly shift team psychological safety.
Frame work as learning, not performance
Teams with high psychological safety understand that their work is uncertain and complex — that mistakes are part of learning, and that the goal is continuous improvement rather than flawless performance. Leaders create this frame through the language they use: "What did we learn?" rather than "What went wrong?"; "That's a useful experiment" rather than "That was a failure."
Be genuinely curious
Leaders who ask good questions and listen carefully to the answers — without rushing to provide their own answers — signal that other people's thinking is valuable. This is one of the most consistent predictors of psychological safety: the quality of the leader's curiosity.
Respond appreciatively to difficult information
When someone raises a concern or delivers bad news, the leader's response sets the tone for the entire team. Responding with curiosity and appreciation — "Thank you for raising this. Tell me more about what you're seeing" — signals that difficult information is welcome. Responding with defensiveness or blame signals the opposite.
Run a Team Psychological Safety Audit
A validated psychological safety assessment provides baseline data on where your team stands and identifies specific areas for development. Our free Team Psychological Safety Audit (available at /diagnostic/team-psychological-safety-audit) measures four dimensions of psychological safety and provides personalised recommendations.
References
Edmondson, A.C. (1999) 'Psychological safety and learning behavior in work teams', Administrative Science Quarterly, 44(2), pp. 350-383.
Edmondson, A.C. (2018) The Fearless Organization: Creating Psychological Safety in the Workplace for Learning, Innovation, and Growth. Hoboken, NJ: John Wiley & Sons.
Frazier, M.L. et al. (2017) 'Psychological safety: A meta-analytic review and extension', Personnel Psychology, 70(1), pp. 113-165.
Google re:Work (2016) Understanding Team Effectiveness. Available at: rework.withgoogle.com.