Claim: Octopuses have three hearts

First requested: June 13, 2026 at 9:18 AM
83%

IsItCap Score

Truth Potential Meter

Very Credible

AI consensusWeak

Grader consensus is weak.
Range 0%–100% (spread Δ100).
The graders diverge. Treat the combined score as uncertain and read the sources carefully.
Read analysis summary

OpenAI Grade

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100%

Perplexity Grade

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Google Gemini Grade

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98%
Shareable summary
Verdict: Questionable
  • No evidence in the pack contradicts the claim; all sources support the three-heart anatomy.
  • The absence of conflicting data makes it difficult to argue against the claim.
/r/octopuses-have-three-hearts

Analysis Summary

The claim that octopuses have three hearts is true. Mainstream sources such as New Scientist and Smithsonian Magazine confirm this anatomical fact, detailing the roles of the two branchial hearts and one systemic heart. There are no credible sources disputing this claim, as it is well-established in marine biology. The unique circulatory system of octopuses is a fascinating aspect of their physiology, further supported by reputable institutions like the Natural History Museum. The models diverge sharply — treat this as higher-uncertainty. OpenAI comes in highest (100%), while Perplexity is lowest (0%). OpenAI expresses higher confidence than Perplexity on this claim. There are no opposing claims regarding the number of hearts in octopuses, as all evidence consistently supports the assertion that they possess three hearts. This consensus among reputable sources indicates a strong agreement on this anatomical feature, leaving no room for uncertainty or dispute in the current understanding of octopus biology.
Jump to source analysis

Source quality

Truth (from sources)10.00 / 10
Source reliability9.00 / 10
Source independence9.00 / 10

Claim checks

Fits established facts10.00 / 10
Logical consistency10.00 / 10
Expert consensus10.00 / 10
Related fact checks

Source Analysis

Common arguments
Supporting the claim
  • New Scientist explains octopuses have three hearts: two branchial and one systemic.
  • Smithsonian Magazine lists three hearts as a key fact, detailing their roles in blood circulation.
  • Natural History Museum confirms three hearts with distinct roles: one for body, two for gills.
Against the claim
  • No evidence in the pack contradicts the claim; all sources support the three-heart anatomy.
  • The absence of conflicting data makes it difficult to argue against the claim.
  • No alternative circulatory system is mentioned in the provided evidence.

Mainstream Sources

Publication

New Scientist

Title

How many hearts does an octopus have?

Summary

New Scientist explains that octopuses possess three hearts: two peripheral hearts that pump blood through the gills to absorb oxygen, and one central heart that circulates the oxygenated blood to the rest of the body. This system compensates for the lower efficiency of their copper-based blood protein, haemocyanin.

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Publication

Smithsonian Magazine

Title

Ten Wild Facts About Octopuses: They Have Three Hearts, Big Brains and Blue Blood

Summary

Smithsonian Magazine lists three hearts as a key fact about octopuses, detailing that two hearts move blood past the gills while the third circulates oxygen-rich blood to the body. It also notes that the systemic heart stops beating when the octopus swims, explaining their preference for crawling.

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Publication

Natural History Museum (UK)

Title

Octopuses keep surprising us - here are eight examples how

Summary

The Natural History Museum confirms that octopuses have three hearts with distinct roles: one circulates blood around the body, while the other two pump it past the gills to pick up oxygen. The museum also explains the blue color of their blood is due to copper in haemocyanin.

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Alternative Sources

No alternative sources were found for this analysis.

Analysis Breakdown

True/False Spectrum (10.0)Source Credibility (9.0)Bias Assessment (9.0)Contextual Integrity (10.0)Content Coherence (10.0)Expert Consensus (10.0)97%

How to read the breakdown

Weakest areas
Source reliability9.0/10Independence9.0/10
  • Truth: how well sources support the core claim.
  • Source reliability: whether the sources have a strong track record.
  • Independence: whether coverage looks one-sided or recycled.
  • Context: missing details (timeframe, definitions, scope) that change meaning.
  • Tip: if graders disagree, rely more on the summary + sources than the single number.

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Methodology