12.1 Wisdom of Crowds and Herd Thinking
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Explore ways that groups fall short of their optimal reasoning ability. There are better and worse ways to aggregate a group's knowledge.
The Lesson in Context
This lesson discusses when groups of people make better or worse judgments than individuals. It leads into the last part of the course, which revolves around group decision making, e.g. as a society.
- Individual judgments can deviate from the truth due to systematic bias and random fluctuation. Reducing shared bias and increasing sample size are ways to improve the effects of Wisdom of Crowds.
- Conformity to the group consensus, illustrated by the Asch experiment, and obedience to a perceived authority in a group, illustrated by the Milgram experiment, are psychological tendencies that affect group decision making, tending to increase herd thinking.
- Confirmation bias can exacerbate other biases in group decision making, such as the motivation to make judgments that conform to the group consensus or agree with the opinion of the authority figure - again, increasing problematic herd thinking.
- When making group decisions using the Denver Bullet Study method, it is important to survey each expert (on matters of fact) and each stakeholder (on matters of value) individually and independently so as to reduce "herd thinking" effects.
- In a somewhat opposite approach, deliberative polling encourages moderated discussion between all participants punctuated by dialogue with the relevant experts, before participants answer a poll to make informed decisions in society. Conformity with other participants as well as "obedience" to (in the sense of taking advice from) the expert panelists are essential features. The result tends to be a convergence of opinions towards moderation on divisive issues.
Takeaways
After this lesson, students should
- Not take for granted that consensus offers the best conclusions.
- Take seriously (but not as absolute!) the consensus of a group which has reasoned about a question in a careful, appropriate way.
- Take seriously (but not as absolute!) the average of a large group's independent estimates of a number, under appropriate conditions.
- Identify shared biases in a given group which may increase the odds of problematic herd thinking rather than helpful wisdom of crowds.
Wisdom of Crowds
- Judgments are genuinely independent, preventing herd thinking.
- Members of the group do not share the same biases.
- There are enough people in the group to balance out random biases or fluctuations (analogous to the need for an adequate sample size).
- Works especially well when estimating a quantity, where errors may be large but are not systematic.
Herd Thinking
- Judgments of individuals are influenced by the judgments of others, leading to groupthink and sometimes polarization.
- Members of the group share biases, which can be exaggerated by discussion and cannot be decreased by averaging judgments.
Meta-analysis
Family Dynamics
- Within a group like a family, the parents may have chosen each other partly due to shared opinions and beliefs, and taught these to their children. The experience of strong consensus and absence of dissent within the family can cause the members to become more confident and more extreme in their beliefs (herd thinking), even if these opinions are quite different from a broader consensus in society. Moreover, it can be difficult for members to break out, since disagreeing with the group can be seen as disloyal, unethical, defiant, and ungrateful.
Congressional Committees
- In Congress, most committees include both Republicans and Democrats. Ideally, this leads to groups whose members have different biases, helping to prevent herd thinking and leading to more considered policy proposals.
Scientific Community
- In science, the ideal is a large community of people with varied biases who pursue investigations independently, and share their findings and ideas periodically. These features help the enterprise of science take advantage of the virtues of wisdom of crowds.
Insofar as the members of the scientific community share the same biases - for example, that they are not demographically representative of humanity at large - this can reduce the efficacy. For this reason, representation in science is important not only for ethical reasons of equity, but also for epistemic reasons.
Everyone agrees, so it must be true.
I trust my guess about how many pages are in this book more than the average of my guess with other people's guesses, because even if I don't have more information than other people, it's MY guess and you should stick with your own guess.
Useful Resources
Recommended Outline
Before Class
Update the Google form in the warm-up polls.
During Class
| 5 Minutes | Introduce the lesson and go over the plan for the day. Make sure people have groups, spokespeople, etc. |
| 30 Minutes | Have the class do the assorted warm-up polls. |
| 40 Minutes | Walk the class through the various jury discussions. |
| 5 Minutes | Do the group problem if time allows. This part is optional. |
Lesson Content
Warm-up Polls
For this discussion section, students will start by filling out a Google form which asks for their best estimate of four quantities (should take 3-5 mins). The form should connect to a spreadsheet which shows how the class is or isn't aggregating live. Depending on the particular setup, this may take some spreadsheet finagling live during class. An example spreadsheet that was used in spring 2023 can be found below.
Wisdom of Crowds Estimates
Make sure to copy the Google form and provide it to the students with a link and/or QR code.
Make sure the students give their best guesses for each question without discussing with any classmates or looking any answers up. Don't reveal the answers until everyone's submitted their responses.
The first poll demonstrates the wisdom of crowds and what happens when there's a systematic bias in people's judgments. It has the following four numerical questions.
- What is the heaviest recorded weight for a feline as of 2013?
922 lbs
- What was the average weight for American men in 1960?
166 lbs
- What is the heaviest recorded weight for a rabbit as of 2013?
55 lbs
- What was the average weight for American women in 2010?
163 lbs
Activity 1
[Brief description of and motivation for the activity]
[Common misconception or thing to look out for.]
[Thing you really need to look out for!]
[Title]
[Useful tip, guideline, or other background.]
Instructions
| [n] Minutes | [Activity.] |
| [n] Minutes | [Activity.] |
Discussion Questions
[Question 1]
[Possible misconception that may need to be corrected and clarified.]
[Intended answer to the above question.]
[Question 2]
[Possible misconception that may need to be corrected and clarified.]
[Intended answer to the above question.]