10.1 Confirmation Bias

Useful Links

• Lesson Slides
• Website Page

Learning Goals

After this lesson, students should

1. Be wary of one's own tendency towards motivated reasoning and confirmation bias.
2. Be able to explain how different forms of confirmation bias (i.e., selective exposure, biased assimilation) can lead to errors.

Definitions

• Confirmation bias

  Also known as myside bias. Seeking or otherwise favoring evidence consistent with what is already believed or what is being tested.

  • Selective exposure

    Selectively seeking or exposing oneself to evidence that is likely to conform to prior beliefs or working hypotheses.

  • Biased assimilation

    Systematically favoring or discounting evidence to render that evidence more compatible with pre-existing beliefs or working hypotheses.

Examples

• Modern social media offer a perfect environment for selective exposure, where one only chooses to view content created by those that already confirm their preexisting worldview or beliefs. Content moderation algorithms of major websites exacerbate the problem by reinforcing one's choice in the type of "desirable" content, leading to the "filter bubble".
• As a counterexample, when testing whether a web form taking an email address has been coded correctly, a programmer not only tries "sensesensibilityscience@berkeley.edu" to see if it works, but also non-email address strings like "https://berkeley.edu", "laf1209#$%^&", "Robert; DROP TABLE Students" to see if it breaks. The programmer actively seeks to disconfirm their hypothesis that "the web form is coded correctly".
• The measured value of the Hubble parameter (which describes the speed of the expansion of the Universe) published over time. The few early measurements are clearly too far away from the currently accepted value and overconfident, but they confirmed the accepted value at that time. As soon as one deviating value was published, a slew of publications finally came to support this new value.

  

Common Misconceptions

• Mistaken quote

  Explanation.

Context

This lesson continues the lessons on cognitive heuristics and biases, reminding us that even careful scientists can fall prey to such human tendencies. 10.2 Blinding will introduce techniques to counter these tendencies. In this lesson, we let students fall into the trap of biased assimilation by asking them to evaluate the same news article that is labelled leftwing for one group and rightwing for the other.

Before

2.2 Systematic and Statistical Uncertainty

Both biased assimilation and selective exposure introduce a systematic bias in our perception and assessment towards a direction that confirms our existing beliefs.

3.2 Calibration of Credence Levels

Actively open minded thinking aims to measure one's avoidance of confirmation bias. It assesses whether one actively seeks out arguments contrary to their prior beliefs and evaluates evidence objectively independently of their beliefs.

9.1 Heuristics

Selective exposure together with the availability heuristic can exacerbate the bias in one's belief.

After

10.2 Blinding

Blind analysis and preregistration are techniques to reduce motivated reasoning during the data collection and analysis process.

Recommended Outline

Before Class

• Print out abstracts, enough to give one to each student.
• Prepare a seating chart.
• Be ready to present a link or a QR code to the Google Form.
• Be ready to create a quick histogram from the Google Form, comparing average ratings of the four articles. Have on hand the key to which abstract is which, so you can label the graph during the big reveal.
• Review PlayPosit and discussion questions and ask faculty, Gabriel, or Emlen any questions you have.
• (Optional) Prepare a presentation.

During Class

• (5 min) Come up with some fun way to assign the roles of spokesperson and notetaker (e.g. earliest birthday in the year, lives furthest from campus). Remind them of the responsibilities of these roles.
• (30 min) Biased assimilation activity.
• (15 min) Go through the discussion questions.

After Class

• Collect answers from notetakers for the forum / plenary.

Lesson Content

Biased Assimilation (Short)

This activity is based on an exhibition at the Exploratorium.

Preparation

1. Multiple topics on which students may already have an opinion:
   1. Should the US have universal health care?
   2. Should you eat more blueberries for your health?
   3. Should parents receive vouchers to pay for private schools?
   4. Should people reduce their social media use?
2. Each topic has multiple arguments for/against, printed redundantly (students are told this).
3. Two envelopes are prepared for each topic, containing the arguments for/against, respectively, brightly marked YES/NO outside.
4. Students are asked to queue and pick a topic and one argument from either of the envelopes for that topic, then goes back to their seat.
5. They can choose to queue again for another argument.
6. At the end, a quick show of hands for whether students initially picked an argument from the side they already agree with. For those that went back, show of hands again for whether they picked from the side they agreed with or not.

Biased Assimilation (Long)

This activity follows the classic study on biased assimilation (Lord, Ross, & Lepper, 1979), where subjects are given identical abstracts of a scientific study, but with conclusions reversed for half of the subjects, and are then asked to assess the validity of the supposed study. Biased assimilation is demonstrated when subjects rate abstracts with belief-congruent conclusions higher than ones with belief-incongruent conclusions.

Instructions

1. Students randomly get one of four abstracts, labeled A, B, C, D.
2. (10 min) Students read their abstract and fill out the Google form.
3. (10 min) The GSI reveals how the abstracts were created (one supporting each position, with flipped abstracts modified to support the opposite conclusion; see bolded abstracts below). Then GSI makes a quick graph of the results and the students discuss how they reflect biased assimilation. If it works as expected, belief-congruent abstracts will be rated higher than belief-incongruent abstracts.
4. (10 min) The GSI shows students the results from the original study (Lord, Ross, & Lepper, 1979) and leads a brief discussion on the implications for biased assimilation in incorporating other evidence.

Google Form

The following questions should be made into a Google form ahead of time.

1. What's your position on the effect of gun control laws on gun violence?
   1. I think gun control laws have no effect on gun violence
   2. I think gun control laws reduce gun violence
2. Which abstract did you read?
   1. A
   2. B
   3. C
   4. D
3. How convincing do you think the evidence in this study is? [Please try to evaluate the evidence independent of your agreement with the conclusion.] (1-10 scale)
4. Briefly, say why you did or didn't find the evidence convincing.

Wason Selection Task

Demo video (from beginning to ~3:10, then ~5:30 to ~6:30)

This is a classic demonstration of humans' performance in deductive reasoning. In the context of confirmation bias, the predominance of a certain wrong answer demonstrates our tendency to seek to confirm a hypothesis, rather than find ways to potentially falsify it.

Make visual slides for this activity for best effect.

Card Puzzle

• Cards have a letter on one side and a number on the other.
• Rule: If a card has a vowel on one side, it has an even number on the other side.
• Which card(s) would you turn over: E, 7, 4, M?
• You may give the following options for a quick show of hands:
  1. E
  2. E and 4
  3. E and 7
  4. E, 7, and 4
  5. E, 7, 4, and M

Bartender

• Cards have an age on one side and what the person is drinking on the other side.
• Rule: If someone is drinking alcohol, they must be over 18.
• Which card(s) would you turn over: beer, 16-yo, 25-yo, apple juice?
• You may give the following options:
  1. Beer
  2. Beer and 16-yo
  3. Beer and 25-yo
  4. Beer, 16-yo, 25-yo
  5. Beer, 16-yo, 25-yo, and apple juice

Now reveal the answers to the above two questions. The tendency to choose E and 4 (specifically 4) for the first task shows our tendency to confirm the rule, rather than seek out ways to falsify it. Humans are much better at the second task, which is logically identical to the first, because it is phrased in the context of policing a social rule.

Blickets

Demo video by Alison Gopnik (30:00 to 35:30)

This is another demonstration that adults tend to seek confirmation of their initial hypothesis, rather than consider unlikely alternative explanations as children do.

Discussion Questions

Discuss the following questions in small groups, and then spend a few minutes to share with the whole class.

1. (5 min) Give two or more examples of selective exposure in a scientific, policy, or everyday context. Explain how the selective exposure leads to error in this particular context.
2. (5 min) Give two or more examples of biased assimilation in a scientific, policy, or everyday context. Explain how the selective exposure leads to error in this particular context.
3. (5 min) How would you go about reducing confirmation bias in your own thinking and information consumption? What are some strategies that individuals or the whole society can adopt to combat confirmation bias?
4. What relevance does confirmation bias play in Vice Provost García Bedolla's Fireside Chat? (Hint. The following passage can help you if you are stuck): "I think, lifting up, what I was just saying about trusting your gut? I think often we, when we are in spaces, it's easy to go along with what's dominant, or it's easy to do what everyone else is doing, or it's easier to be part of the crowd. And I think often we see opportunities or we see things that don't feel quite right and doing something about that or going down that road feels really risky. But what I like to tell my students is any trend, if you can see it it's over. And so in fact, building something new may be very difficult, but that's where the real payoff comes. And to just trust that you, we stand on the shoulders of giants and that you are here representing lots of people like you. And so, if you see something wrong or see a place where change needs to happen or

see something that you think is important to either change or do or influence, that you trust yourself, that you're right in that analysis and that you are willing to take the risk."