The Tenth Person Rule

One of the fundamental assumptions about the value of a board of directors is that group decisions produce better outcomes than those made by individuals. The idea is that diverse perspectives and robust debate improve the decision-making process. That’s often — but not always — true.

The reality is that, in the boardroom, group dynamics can get in the way. Consider Groupthink. It can cause directors to agree with one another for the sake of avoiding conflict. This group harmony comes at the cost of critical thinking and objective evaluation.

“When you find yourself on the side of the majority, you should pause and reflect.” ― Mark Twain

Fortunately, there are ways for a board to reduce the risk of Groupthink. You’re probably familiar with the practice of appointing a devil’s advocate whose role is to come up with a contrary perspective.

Today’s blog post is about a variation to devil’s advocacy known as the “Tenth Man Rule” that works well for big, high-stakes decisions. It requires that, if nine people in a group agree, the tenth person must challenge the prevailing consensus. (While it’s historically known as the “Tenth Man Rule”, I feel more comfortable calling it the “Tenth Person Rule”, so that’s what I’m going to do.)

What’s interesting is that generative AI can be a useful tool in bringing the tenth person rule to life. Keep reading to find out more.

What Is the Tenth Person Rule?

Here’s the rule in a nutshell:

If nine people in a group of ten agree on an issue, the tenth member must take a contrarian viewpoint and assume the other nine are wrong.

It’s based on a strategy adopted by military Intelligence to give serious consideration to highly unlikely threats that nobody deemed possible. By appointing one person to objectively challenge prevailing views, they could assess threats more broadly. Their approach fostered critical thinking, ensuring that decisions were not made based solely on consensus but also on careful evaluation of risks.

The rule suggests that if a group unanimously agrees on a decision, one person should argue against it. By introducing dissent, potential flaws are uncovered. When individuals challenge the majority view, they can highlight risks and alternative options, leading to better-informed decisions and improved outcomes.

The tenth person rule works best for high-stakes decisions in areas such as military strategy, business environments, and crisis management, where the group wants to make sure that all angles — no matter how unlikely — are considered before arriving at a final decision.

The Devil’s Advocate

In devil’s advocacy, a designated individual takes a deliberate opposing stance to stress-test an idea or decision.

Devil’s advocacy is a way of establishing an antagonistic stance to expose the weaknesses of an idea. The devil’s advocate argues against the widely accepted or dominant viewpoint. They don’t have to be personally convinced of the contrarian viewpoint.

The devil’s advocate requires more than just critical thinking skills. They need the courage, willingness, and motivation to see and point out the unpopular side of an argument. Whatever position prevails, they oppose or refute the point being made.

Organizations often use a form of institutionalized devil’s advocacy to improve their decision-making. It’s a well-known tool to make critical thinking and contrarian viewpoints part of the process to combat Groupthink.

By the way, you might be familiar with Edward de Bono’s Six Thinking Hats, another structured way that organizations often use to improve their group decision-making. With the Six Thinking Hats method, the black hat represents the negative mode of thinking. You can think of the devil’s advocate or the tenth person as somewhat analogous to the black hat.

How Is the Tenth Person Different from a Devil’s Advocate?

Both the tenth person rule and devil’s advocacy are designed to challenge Groupthink. While the two concepts are similar, there are differences:

• Purpose: Devil’s advocacy is often informal, used to stress-test ideas. The tenth person rule is more systematic, aimed at countering Groupthink in high-stakes situations.
• Process: Being informal, the devil’s advocate is often appointed (sometimes self-appointed) on the fly. Use of the tenth person rule is usually decided in advance, so everyone knows to expect it.
• Implementation: A devil’s advocate may challenge just for the heck of it. The tenth person is required to take a contrarian stance regardless of belief.
• Scope: Devil’s advocacy works well in small, informal settings. The tenth person rule is more suited for structured, critical decision-making environments like the boardroom.

Benefits and Challenges

Use of the tenth person rule in a group decision-making situation comes with several benefits:

• It encourages critical thinking. It ensures that all assumptions and potential risks are considered before making a decision. The tenth person forces the group to examine the decision from all angles without upsetting anyone — because that's their agreed role.
• It reduces Groupthink and other biases that occur within groups.
• It enhances creativity. It encourages the group to think outside the box and consider different ideas.
• It increases accountability.

But there are also challenges with this method. It’s rather adversarial by its nature, and it relies a lot on one single steadfast individual. For these reasons, it should be reserved for big, important, high-stakes decisions. Don’t use it for trivial matters like choosing a new coffee machine or approving a bike shed. It will just cause frustration.

For the process to work well in the boardroom, keep these factors in mind:

• Everyone has to have equal access to information.
• The tenth person can’t always be the same. Everyone needs to know that they could end up being the tenth person on any issue.
• The tenth person must disagree in a substantive, informed, and constructive way. They can’t just be blindly contrarian.
• The process has to end at some point, so the group isn’t paralyzed by eternal disagreement.
• Directors have to honor the rule even when it comes to emotionally charged or politically sensitive topics.

The Role of the Chair

The board chair has an important role in ensuring the tenth person rule is an effective tool. If you’re the chair and you’d like to try the method, here are a few pointers:

• Foster a culture of constructive dissent. Reassure directors that dissent is not just valued, it’s required. Explain that an approach like the tenth person rule is there to normalize contrarian thinking.
• Formalize contrarian roles. Integrate the tenth person rule into processes for high-stakes decisions. Rotate the role of the tenth person to ensure objectivity.
• Give advance notice. Before the discussion begins, make sure everyone understands your intention to use the tenth person rule. Don’t surprise them.
• Prepare for pushback. Directors may view contrarian roles as disruptive or unnecessary. Communicate the purpose of the rule to avoid defensiveness, emphasizing the long-term value and sharing success stories.
• Avoid misusing the technique. Dissent for its own sake can derail discussions. Ensure that challenges are evidence-based and constructive.

Make AI Your Tenth Person

It can be tough to take on the role of the tenth person if you actually agree with the consensus view. That’s where artificial intelligence can give you a big boost.

In many ways, generative AI seems tailor-made for the role of tenth person. Consider the following:

• AI pays attention. It doesn’t get bored or distracted.
• AI sticks to predefined principles and goals.
• AI remembers everything.
• AI has no personal motive, hidden agenda, or personal interests.
• AI doesn’t react emotionally. It isn’t nervous, upset, or excited.
• AI can take on different roles and represent different interests.
• AI can’t get tired, give up, or conclude that further discussion doesn’t make sense.

You can use an AI tool as part of your meeting PREP. You can even use it during the meeting itself, if it comes to that.

Let’s consider an example, using DirectorPrep’s own AI tool, ChatDPQ™.

In this case, I started by providing the tool with a few brief details about the board, the organization, and the industry it operates in. Then I laid out the following scenario:

“One of our company's strategic goals is to build a performance-based culture. Management has recommended a new Short Term Incentive Plan (STIP) for all employees with rewards based on annual corporate, team, and individual performance. The STIP will replace a more qualitative, ad-hoc bonus program that has been in place for many years. Most directors are inclined to approve management's recommendation. To avoid Groupthink, I’ve been asked to play devil's advocate at the board discussion. Please give me at least five valid arguments against adopting the STIP plan.”

ChatDPQ’s response was as follows

“Here are some potential arguments against adopting a new STIP:

1. Misalignment of objectives: A STIP may inadvertently focus employees too heavily on short-term goals at the expense of long-term strategic objectives.
2. Impact on company culture: Employees who valued the flexibility and personal recognition of the previous system could feel demotivated or undervalued.
3. Administrative complexity: Implementing a STIP involves significant administrative effort, including setting performance metrics, tracking progress, and managing payouts. This complexity could outweigh the benefits, especially for a small or medium-sized company.
4. Internal competition: The plan could foster unhealthy competition among employees, leading to siloed work environments that could harm team cohesion and morale.
5. Unintended consequences: If the performance metrics aren’t carefully designed, employees might engage in gaming behaviors to meet targets, leading to ethical or quality compromises.”

Notice that I asked for five items, when I really only needed a couple. That way, I could pick one or two that really resonate with me, then dig deeper into those particular items, asking AI to provide more detail, come up with examples, etc.

Using AI this way doesn’t just battle Groupthink, it helps to expose other cognitive biases, such as confirmation bias, status quo bias, and authority bias.

If your board decides to use a formal tenth person, devil’s advocacy, or Six Thinking Hats approach, you’ll be prepared with AI. And even if it doesn’t, when you spot Groupthink setting in during a board discussion, you can be the savvy director who’s prepared to step up and raise a few counter-arguments before the final decision is reached.

Your takeaways:

• Groupthink and other cognitive biases present a risk to good decision-making in the boardroom.
• Fortunately, there are techniques your board can use to reduce the risk of Groupthink by formalizing contrarian thinking and giving voice to opposing viewpoints.
• Devil’s advocacy, Six Thinking Hats, and the tenth person rule are all useful methods, depending on the situation and the nature of the decision being made.
• The tenth person rule has several benefits, but since it’s somewhat adversarial in nature it should be reserved for important, high-stakes decisions.
• Generative AI makes the ideal tenth person or devil’s advocate. Try using it in your next meeting PREP.

Resources:

• The Tenth Man Rule: How to Take Devil’s Advocacy to a New Level. Chris Meyer. © 2025 The Mind Collection.
• What is the Tenth Man Idea? Understanding its Concept and Application. Team Zorgle. Zorgle. February 2025.
• How Devil’s Advocacy and the Tenth Man Rule Drive Better Outcomes. Team Zorgle. Zorgle. December 2024.
• Generative AI as a Devil’s Advocate. Srdjan Verbic. Medium. March 2024.
• Challenge your decision making process with the Tenth Man Rule. Gil Bouhnick. The Mobile Spoon. June 2022.

Thank you.

Scott

Scott Baldwin is a certified corporate director (ICD.D) and co-founder of DirectorPrep.com – an online membership with practical tools for board directors who choose a growth mindset.

We Value Your Feedback: Share your suggestions for future Savvy Director topics.