Diverse group collaboratively making decisions, with interconnected brains symbolizing knowledge flow and abstract elements representing time and learning.

Group Decision-Making: Can More Minds Lead to Better Choices?

Theo Raines in Mind & Education August 2025 • 4 min read.

"Explore the surprising trade-offs between group size and individual competence in making sound judgments, and how to optimize decision-making in teams."

In many situations, we face a balancing act: increasing the number of people involved versus the time each person has to develop expertise. For instance, when forming a committee with a set budget, do we opt for more members with less individual preparation, or fewer members with more in-depth understanding? This question delves into how the size of a group, the development of its members' skills, and the chances of making the best collective decision intertwine.

Collective decision-making has long been praised for its potential to harness diverse insights. As Aristotle noted, a group can sometimes surpass the best individuals, pooling 'part of virtue and practical wisdom' from many. This concept suggests that a well-formed group decision could be more competent than any single member's judgment.

However, the traditional view, epitomized by Condorcet's Jury Theorem, assumes that each juror's competence is fixed. In reality, competence evolves over time, especially during group discussions or learning. This evolution, influenced by the variety of backgrounds within the group, plays a crucial role in determining the optimal structure for effective decision-making.

The Jury Theorem: A Classic, But Is It Complete?

Diverse group collaboratively making decisions, with interconnected brains symbolizing knowledge flow and abstract elements representing time and learning.

Condorcet's Jury Theorem provides a foundational understanding of collective decision-making. It posits that if each member of a jury has a greater than 50% chance of making the correct decision, then increasing the size of the jury increases the probability of reaching a correct verdict, approaching certainty as the jury grows infinitely large.

However, this theorem rests on assumptions that don't always hold true in real-world scenarios. Key limitations include:

Fixed Competence: Assumes individual competence remains static, failing to account for learning or influence within the group.
Independence: Requires jurors to vote independently, ignoring potential correlations or biases.
Equal Competence: Often assumes all jurors possess the same level of competence, neglecting the value of diverse expertise.

Realistically, committee members or voters often influence one another, learn new information, and bring different levels of knowledge to the table. For instance, applying the basic jury theorem to committee formation suggests making the committee as large as resources allow. However, practical experience shows that excessively large committees can become unwieldy and ineffective [Fra82], indicating the importance of factors beyond mere size.

Toward Better Decision-Making Models

This research underscores the intricate relationship between group size, competence development, and decision-making quality. It moves beyond the traditional jury theorem by considering how individual learning, diverse perspectives, and communication dynamics shape group competence. Future research should focus on refining our understanding of how these factors interact, paving the way for more effective strategies for building competent and collaborative decision-making bodies. As we better grasp these dynamics, we can expect to see enhanced decision-making across diverse settings, from corporate boards to public policy forums.

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This article is based on research published under:

DOI-LINK: https://doi.org/10.48550/arXiv.2404.09523,

Title: More, Better Or Different? Trade-Offs Between Group Size And Competence Development In Jury Theorems

Subject: econ.th

Authors: Gustaf Arrhenius, Klas Markström

Published: 15-04-2024

Everything You Need To Know

What is Condorcet's Jury Theorem and what are its limitations in real-world group decision-making?

Condorcet's Jury Theorem is a foundational concept in collective decision-making, asserting that if each member has a greater than 50% chance of making the correct decision, increasing the jury's size increases the probability of a correct verdict. However, it simplifies real-world scenarios. The theorem assumes fixed competence, neglecting learning within the group. It also requires independent voting and equal competence among members, which rarely occurs. In reality, group members influence each other, share information, and possess varying levels of expertise, making the theorem's assumptions often unrealistic and its application limited.

How does the concept of evolving competence challenge the traditional views on group decision-making?

Traditional models, such as Condorcet's Jury Theorem, often assume that individual competence remains static. However, in practical situations, competence evolves. During group discussions and learning, the variety of backgrounds within the group influences this evolution. This challenges the traditional views by showing that group size and composition affect not only the initial competence but also how that competence develops over time. The dynamics of learning and influence within a group become crucial factors in determining the optimal structure for effective decision-making, shifting focus from fixed individual capabilities to the growth and interaction within the group.

Why might a larger committee not always lead to better decisions, and what factors contribute to this?

While increasing the number of people involved in decision-making can harness diverse insights, a larger committee is not always better. The basic jury theorem might suggest maximizing committee size, but practical experience shows that excessively large committees can be unwieldy and ineffective. Important factors contributing to this include the time each member has to develop expertise, communication dynamics within the group, and the potential for the group to become bogged down in discussions. A balance must be struck between the benefits of diverse perspectives and the costs of decreased efficiency and deeper individual understanding.

How does Aristotle's view on collective decision-making compare with the principles of Condorcet's Jury Theorem, and where do they diverge?

Aristotle highlighted the potential of a group to surpass the best individuals by pooling 'part of virtue and practical wisdom.' This suggests that a well-formed group decision could be more competent than any single member's judgment. Condorcet's Jury Theorem aligns with this by emphasizing the value of multiple perspectives and the increasing probability of a correct decision with more participants. However, they diverge in their assumptions. Aristotle's view implicitly acknowledges the value of diverse expertise and the potential for learning and growth within a group. Condorcet's theorem, in its basic form, assumes fixed competence, neglecting the dynamic interplay and knowledge exchange that Aristotle's view embraces.

In what ways can understanding the interplay between group size, competence development, and diverse perspectives enhance decision-making strategies?

Understanding this interplay allows for the creation of more effective decision-making strategies. It moves beyond the traditional focus on group size to consider factors like individual learning, the variety of backgrounds, and communication dynamics. By recognizing that competence evolves over time and is influenced by group interactions, organizations can design committees or teams that maximize learning, encourage diverse perspectives, and foster effective communication. This holistic approach helps in building more competent and collaborative decision-making bodies. Such strategies improve the quality of decisions across different settings, from corporate boards to public policy forums, leading to better outcomes by considering the complex interplay of individual and group dynamics.