Choiceology with Katy Milkman

Episode: How a Single Source of Information Can Seem Like Several

Released: August 11, 2025
Host: Katy Milkman (Behavioral Scientist, Wharton Professor, Author)
Featured Guest: Florian Zimmermann (Professor of Economics, University of Bonn)
Additional: Joe Schwartz (Director, Office for Science and Society, Professor of Chemistry, McGill University)

Episode Overview

This episode explores "correlation neglect"—a cognitive bias where people treat information repeated from a single source as if it came from multiple independent sources. Host Katy Milkman unpacks how this bias distorts our judgments—with stories ranging from viral water bottle fads to the legacy of vitamin C megadosing promoted by Nobel laureate Linus Pauling. Katy also dives into scientific research on the topic, interviews an expert, and offers advice for smarter information consumption.

Key Discussion Points & Insights

1. Viral Products and the Illusion of Broad Consensus

[00:10 – 02:41]

• The frenzy over the Stanley Quencher water bottle serves as a modern example:
  • What appeared as widespread organic enthusiasm was, in reality, a coordinated Influencer Marketing campaign initiated by a few marketers who convinced the brand to target a new demographic.
  • The product’s sudden omnipresence made it seem like "everyone independently loved it."
• Quote: "Soon it looked like everyone loved the Stanley Quencher. What we saw were lifestyle creators and wellness influencers showing off their cups. What we didn't necessarily see was the affiliate connection." — Katy Milkman [01:40]
• Sales skyrocketed ($73M in 2019 to $750M in 2023) as people mistook repeated, correlated hype for genuine, widespread acclaim.
• Key Insight: We often fail to recognize when the “buzz” is echoing from a single well-placed source, overvaluing the apparent consensus.

2. The Linus Pauling & Vitamin C Case Study

[03:25 – 13:56]

• Joe Schwartz recounts how Linus Pauling, a highly respected two-time Nobel laureate, became the source of a vitamin C craze:
  • Pauling promoted megadoses of vitamin C, based on anecdotal evidence from himself and his wife, which was publicized through books and media.
  • Respect for Pauling’s accomplishments led to trust in his claims—media and supplement companies repeated these, creating the illusion of independent support.
  • Quote: "It was Linus Pauling, who, you know, was arguably the greatest chemist of the times. If you've ever heard of the healing properties of vitamin C, Linus Pauling is likely the reason why." — Joe Schwartz [06:38]
  • Multiple scientific studies failed to find strong evidence for Pauling’s claims, yet the idea persisted due to its repetition from "independent" sources.
• Schwartz emphasizes: "When you see articles all over the place, even though they all start from the same bit of information...you just think, you know, well, all of these articles, they can't all be wrong." [10:11]

Memorable Moment: Joe Schwartz describes scientists’ reluctance to publicly challenge Pauling—even when he misused correlation-causation logic—because of his stature.

• Quote: "Here is this hero...throwing up that graph and saying conclusively that this demonstrated that taking more vitamin C would reduce heart disease. Nobody said anything." [12:00]

3. Correlation Neglect Explained (With Florian Zimmermann)

[16:45 – 24:40]

• Interview with Florian Zimmermann details the mechanics of "correlation neglect":
  • Definition: "If people get information from multiple sources and these sources are somehow connected...if they neglect this correlation...this is then what we mean by correlation neglect." [16:52]
  • Everyday examples: When friends, colleagues, or media outlets repeat information that ultimately traces back to the same origin, listeners treat it as multiple independent endorsements.
  • Key experimental finding: People average correlated sources as if they are independent, systematically biasing their conclusions.
• Katy clarifies: “If I neglect that [the same expert was quoted in both the radio and news program], I might put too much emphasis on that information, think it's higher quality than it is.” [19:33]
• Consequence: Excessive confidence in repeated—but not truly independent—information.

4. Why Do We Fall for Correlation Neglect?

[20:16 – 21:44]

• Causes include:
  • Not noticing that different sources are actually related/derived from a single source.
  • Failing to recognize the impact of this inaccuracy on personal beliefs.
• Zimmermann says: "It's not that people don't know how to correct for this bias. So it must be something more along the lines of either failing to notice the correlation structure or failing to notice that there is a problem with this correlation structure." [21:44]

5. Can We Fix or Avoid this Bias?

[22:14 – 23:58]

• Research shows that prompting people to be vigilant about possible correlation among sources significantly reduces the bias.
• Quote: "If you really put an alarm that says, look, be careful, watch out for this particular structure, then they actually do the right thing." — Florian Zimmermann [22:28]
• Practical advice: Remind yourself to trace the origin of information, especially if it seems to have wide support.

6. Translating Science to Daily Life

[24:47 – 25:55]

• Katy Milkman reflects:
  • Now, she habitually checks whether multiple recommendations or alarms all stem from a single source.
  • Strategy: Pause to ask, “Are these independent observations, or is this the same concern repeated?” [24:47]
  • Warns not to dismiss all consensus (as genuine, independently replicated findings are valuable), but to remain alert for “illusory consensus” based on repetition.

Notable Quotes & Memorable Moments

• On the Stanley Quencher trend:
  "We figured they were truly a superior drinking vessel and not the product of a single social marketing campaign." — Katy Milkman [02:26]

• On Pauling’s influence:
  "When you're a Nobel Prize winner, you're basically scientific royalty, so anything that you say gets listened to." — Joe Schwartz [07:00]

• On repeated information:
  "You repeat something often enough and it becomes true by repetition." — Joe Schwartz [09:15]

• On correlation neglect in media:
  "By sort of consuming different news outlets, you're gonna be exposed to correlated information." — Florian Zimmermann [19:13]

• On correcting the bias:
  "If you really put an alarm that says, look, be careful, watch out for this particular structure, then they actually do the right thing." — Florian Zimmermann [22:28]

• On practical habit:
  "Simply asking, what's the source? And is it the same? When we hear related news, gossip, or advice can help us avoid placing too much faith in, say, vitamin C. It's a small mental habit that can make a big difference in how we judge what's credible and what's not." — Katy Milkman [25:35]

Important Segment Timestamps

• [00:10–02:41] — Stanley Quencher phenomenon and modern correlation neglect
• [03:25–13:56] — The Vitamin C megadose legend: Linus Pauling and the spread of his claims
• [16:45–24:40] — Interview with Florian Zimmermann: Defining and diagnosing correlation neglect, underlying causes, and solutions
• [24:47–25:55] — Katy’s personal reflections and advice for listeners

Takeaway Lessons

• Be skeptical of apparent consensus: When hearing the same advice or enthusiasm from several places, ask yourself whether you're actually hearing echoes from a single source.
• Healthy skepticism involves tracing information to its roots—not reflexively dismissing widely validated facts, but carefully differentiating independent verification from mere repetition.
• Cultivate a mental habit of asking about the provenance of information before letting it influence important decisions.

Resources

• More on this topic: See choiceology show notes, Florian Zimmermann’s research, and Joe Schwartz’s work.
• For decision-improvement tips: Katy Milkman’s book How to Change and her Substack newsletter Milkman Delivers.

Summary prepared for listeners who want the episode’s full insights without missing a beat.