I've had a bit more time to research Psychological Safety in the workplace.

In the Building a psychologically safe workplace TED talk, Amy Edmondson provides three examples of workplace silence, when voice was necessary:

• A night shift nurse, who feels the dosage looks wrong, considers calling the doctor at home to double check ... but remembers the disparaging comments he made about her abilities last time she called ... so she doesn't make the call, putting the patient at risk.
• A junior co-pilot, bullied relentlessly by his senior officer, becomes too frightened to question the senior officer's actions ... resulting in a fatal air crash.
• An executive, new to the company, is too scared to ask awkward questions about a proposed takeover that everyone else is enthusiastic about.

Why do these sorts of incidents happen?

• No-one wants to look ignorant and incompetent!
• Don't want to look ignorant? Don't ask questions.
• Don't want to look incompetent? Don't admit weakness or mistake.
• Don't want to look intrusive? Don't offer ideas.
• Don't want to look negative? Don't criticize the status quo.

The above "Impression Management" strategy for self protection works. It turns out that humans have evolved to be pretty good at "Impression Management" -- in fact, most folks have mastered it well before they reach high school. This matters because not asking stupid questions robs an organisation of vital learning and innovation opportunities.

Psychologically Safe Workplaces

Psychological Safety is a belief that you will not be punished or humiliated for speaking up with ideas, questions, concerns, or mistakes. In a psychologically safe workplace, you are expected to speak up! For managers to create such an environment, Amy suggests:

• Frame the work as a learning problem, not an execution problem.
• We need everyone's brains and voices in the game.
• Acknowledge your own fallibility. Provide safety for speaking up.
• Be a model of curiosity. Ask a lot of questions yourself.

Note that "Psychological Safety" is orthogonal to "Motivation and Accountability". Most organisations need both. If you have neither, well, you just have apathy. :)

References

• Psychological Safety (wikipedia)
• Building a psychologically safe workplace TED talk by Amy Edmondson (~11 minutes)
• Team Effectiveness Discussion Guide (google doc)
• Manager Actions for Psychological Safety (google doc)
• Conflict in Teams (notes that trust is key to achieving Psychological Safety)