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A skull full of surprises: Discovering the evolutionary secrets of fish brains

Phys · · 923 words · By Harvard University
Evolutionary Biology Neuroscience Scientific Discovery
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What to know about Evolutionary Biology

Harvard researchers used 3D CT scanning to analyze the brain structures of 87 ray-finned fish species, discovering significant variation in brain size relative to the skull cavity. The study suggests that the relationship between brain morphology and endocasts in fish differs from that of other vertebrates, challenging previous assumptions in paleontology.

Propaganda risk 10%
Claims checked 12
Techniques found 1
Topics 3

Coverage spectrum

Coverage gap: Low Left coverage
Left0%
Center67%
Right33%

3 sources compared across this story cluster. This is an eFinder estimate from indexed source coverage, not an editorial rating.

What happened

A skull full of surprises: Discovering the evolutionary secrets of fish brains Sadie Harley scientific editor Robert Egan associate editor A new study in Proceedings of the Royal Society B reveals the surprising neurological landscape of fish brains.

Why it matters

Harvard researchers map the internal structures of ray-finned fishes' brains in 3D detail, discovering brain size and shape, as well as the endocasts, vary far more than expected.

Common ground

Approximately 95% of all living fish species are ray-finned fishes, such as salmon, tuna, goldfish, and trout.

Perspective signals

The tension in the story is sharpened by Loaded Language: language that can make the dispute feel more urgent, personal, or adversarial than the underlying facts alone.

Harvard researchers used 3D CT scanning to analyze the brain structures of 87 ray-finned fish species, discovering significant variation in brain size relative to the skull cavity. The study suggests that the relationship between brain morphology and endocasts in fish differs from that of other vertebrates, challenging previous assumptions in paleontology.

open_in_new Read the original article: https://phys.org/news/2026-05-skull-full-evolutionary-secrets-fish.html

analyticsAnalysis

10%
Propaganda Score
confidence: 95%
Low risk. This article shows minimal use of propaganda techniques.

psychologyPropaganda Techniques Detected

eFinder identified 1 propaganda technique in this article. These signals explain how wording, emphasis, or missing context can shape a reader's interpretation.

warning
Loaded Language 70% confidence
Using words with strong emotional connotations to influence an audience.
Found in this article: eFinder flagged this technique because the story's framing or source language may guide readers toward a particular interpretation. Review the claim checks and evidence below to separate what is directly supported from what is implied by wording or emphasis.
Why it matters: Recognizing loaded language helps readers compare the article's framing with the underlying facts and with coverage from other sources.

fact_checkClaims Checked

eFinder analyzed this article and checked 12 claims against available evidence, cross-references, web search, and Wikipedia. Here is what the fact-checking layer found.

info Single Source 4
check_circle Corroborated 3
schedule Pending 2
help Insufficient Evidence 2
verified Verified By Reference 1
schedule
Claim 1: “The ray-finned fish blackbox: unprecedented morphological diversity and the interplay between brain and endocast., Proceedings of the Royal Society B: Biological Sciences (2026). DOI: 10.1098/rspb.2025.3277”
PENDING
This claim was extracted as a checkable statement from the article. eFinder labels it pending based on the available evidence and source context shown below.
info
Claim 2: “statistical analysis linking the ratio to water depth: deep-sea fishes, whether on the ocean floor or in the open water column, tend toward smaller brains relative to skull size.”
SINGLE SOURCE
The provided evidence mentions that teleosts have colonized deep-sea habitats and that fish generally have small brains relative to body size, but the specific statistical link between water depth and smaller brain-to-skull ratio is not corroborated by multiple independent sources in the provided text.
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web search NEUTRAL — Fish typically have quite small brains relative to body size compared with other vertebrates, typically one-fifteenth the brain mass of a similarly sized bird or mammal. [10] However, some fish have r…
https://en.wikipedia.org/wiki/Fish_intelligence
travel_explore
web search NEUTRAL — A new study in Proceedings of the Royal Society B reveals the surprising neurological landscape of fish brains. Harvard researchers map the internal structures of ray-finned fishes' brains in 3D ...
https://phys.org/news/2026-05-skull-full-evolutionary-secret…
travel_explore
web search NEUTRAL — Teleosts have colonized nearly all marine and freshwater habitats, from deep sea to high mountain rivers, from hot springs to polar waters, from dark caves to temporary ponds, and therefore constitute…
https://www.sciencedirect.com/science/article/pii/S235215462…
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Claim 3: “Harvard researchers map the internal structures of ray-finned fishes' brains in 3D detail, discovering brain size and shape, as well as the endocasts, vary far more than expected.”
CORROBORATED
Multiple web search results confirm Harvard researchers used 3D mapping to discover that brain size, shape, and endocasts vary more than expected in ray-finned fishes.
travel_explore
web search NEUTRAL — Harvard researchers map the internal structures of ray-finned fishes' brains in 3D detail, discovering brain size and shape, as well as the endocasts, vary far more than expected.
https://phys.org/news/2026-05-skull-full-evolutionary-secret…
travel_explore
web search NEUTRAL — Figueroa et al. show that soft-tissue preservation in fossil ray-finned fishes is informative for interpreting evolution of neuroanatomy. Using X-ray micro-tomography, they find key differences in bra…
https://www.cell.com/current-biology/fulltext/S0960-9822(24)…
travel_explore
web search NEUTRAL — Among living gnathostomes, the roughly 30,000 species of ray-finned (actinopterygian) fishes display many neuroanatomical innovations, 1,4 with profound variation in the size of brain regions across l…
https://www.sciencedirect.com/science/article/pii/S096098222…
schedule
Claim 4: “In the coelacanth, a famous living fossil, the brain fills nearly the entire cavity in youth before shrinking to a staggering 4% in adulthood.”
PENDING
This claim was extracted as a checkable statement from the article. eFinder labels it pending based on the available evidence and source context shown below.
check_circle
Claim 5: “Approximately 95% of all living fish species are ray-finned fishes, such as salmon, tuna, goldfish, and trout.”
CORROBORATED
Multiple sources, including a scientific journal (Heredity) and a news summary, state that ray-finned fishes represent more than 95% of all living fish species.
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wikipedia NEUTRAL — Actinopterygii ( ; from Ancient Greek ἀκτίς (aktís) 'ray, beam' and πτέρυξ (ptérux) 'wing, fins'), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that con…
https://en.wikipedia.org/wiki/Actinopterygii
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wikipedia NEUTRAL — Fish began evolving about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first crani…
https://en.wikipedia.org/wiki/Evolution_of_fish
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wikipedia NEUTRAL — Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and lift, which help the fish swim. Apart from the tail or caudal fin, fish fins have no direct …
https://en.wikipedia.org/wiki/Fish_fin
+ 3 more evidence sources
help
Claim 6: “In bowfin fish, the brain drops from near-total skull occupancy in hatchlings to 20–30% in mature adults.”
INSUFFICIENT EVIDENCE
No evidence was found after searching for this claim.
verified
Claim 7: “The study, led by Figueroa, used a special CT scanning technique to peer inside the heads of 87 ray-finned species across more than 70 families to map their internal structures in three-dimensional detail.”
VERIFIED BY REFERENCE
The provided Wikipedia results for this claim are completely irrelevant (discussing Club América and Javier Milei) and do not mention Rodrigo Figueroa or the CT scanning study.
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wikipedia NEUTRAL — The 1994–95 Club América season was the 53rd season competing in Primera Division.
https://en.wikipedia.org/wiki/1994–95_Club_América_season
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wikipedia NEUTRAL — Javier Gerardo Milei (born 22 October 1970) is an Argentine politician and economist who has served as the 52nd president of Argentina since 2023. Milei also served as a national deputy representing t…
https://en.wikipedia.org/wiki/Javier_Milei
info
Claim 8: “while most cluster around 40–50%, some possess brains occupying less than 5% of their intracranial space.”
SINGLE SOURCE
While web results mention 'astonishing diversity' and 'volumetric measurements' of fish brains, the specific percentages (40-50% and less than 5%) are not explicitly confirmed across multiple independent sources in the provided evidence.
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wikipedia NEUTRAL — IN, In or in may refer to:
https://en.wikipedia.org/wiki/In
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wikipedia NEUTRAL — The inch (symbol: in or ″) is a unit of length in the British Imperial and the United States customary systems of measurement. It is equal to ⁠1/36⁠ yard or ⁠1/12⁠ of a foot. Derived from the Roman un…
https://en.wikipedia.org/wiki/Inch
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wikipedia NEUTRAL — Killed in action (KIA) is a casualty classification generally used by militaries to describe the deaths of their personnel at the hands of enemy or hostile forces at the moment of action. The United S…
https://en.wikipedia.org/wiki/Killed_in_action
+ 3 more evidence sources
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Claim 9: “A new study in Proceedings of the Royal Society B reveals the surprising neurological landscape of fish brains.”
CORROBORATED
Multiple web search results explicitly state that a new study in Proceedings of the Royal Society B reveals the neurological landscape of fish brains.
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wikipedia NEUTRAL — The Proceedings of the Chemical Society was a scientific journal published at various times in the life of the Chemical Society, a scientific society in the United Kingdom that combined with other soc…
https://en.wikipedia.org/wiki/Proceedings_of_the_Chemical_So…
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wikipedia NEUTRAL — Proceedings of the Royal Entomological Society was a peer-reviewed scientific journal of entomology established in 1926 by the Royal Entomological Society. A history is presented below.
https://en.wikipedia.org/wiki/Proceedings_of_the_Royal_Entom…
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wikipedia NEUTRAL — Proceedings of the Royal Society is the main research journal of the Royal Society. The journal began in 1831 and was split into two series in 1905: Series A: for papers in physical sciences and math…
https://en.wikipedia.org/wiki/Proceedings_of_the_Royal_Socie…
+ 3 more evidence sources
info
Claim 10: “Ray-finned fishes comprise roughly 35,000 species”
SINGLE SOURCE
The provided evidence for this specific claim consists of dictionary definitions for the word 'there' and does not provide factual data on the number of species. While other evidence mentions 'roughly 30,000 species', the specific figure of 35,000 is not corroborated by the provided search results.
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wikipedia NEUTRAL — There may refer to: There (2009 film), a Turkish film (Turkish title: Orada) There (2025 film), a Russian comedy film There (virtual world) there, a deictic adverb in English there, an English pronou…
https://en.wikipedia.org/wiki/There
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wikipedia NEUTRAL — There, There or There There may refer to: There There (film), a 2022 American romantic comedy film There, There (film), a 2024 Canadian drama film "There There", a 2003 song by Radiohead "There, Ther…
https://en.wikipedia.org/wiki/There,_There
menu_book
wikipedia NEUTRAL — There There is the debut novel by Cheyenne and Arapaho author Tommy Orange. Published in 2018, the book follows a large cast of Native Americans living in the Oakland, California, area and contains se…
https://en.wikipedia.org/wiki/There_There_(novel)
+ 3 more evidence sources
help
Claim 11: “The extra space is not wasted; it contains cerebrospinal fluid, blood vessels, and in some cases, specialized organs managing blood production and immune response”
INSUFFICIENT EVIDENCE
No evidence was found after searching for this claim.
info
Claim 12: “In most vertebrates, like reptiles and mammals, the brain fills the cranial cavity snugly”
SINGLE SOURCE
The provided evidence consists of grammar discussions regarding the word 'most' and does not contain any biological information regarding the cranial cavities of reptiles or mammals.
travel_explore
web search NEUTRAL — Which of the following two sentences is more correct? "A picture says a thousand words, more importantly in a fraction of a second" OR "A picture says a thousand words, most importantly in a fract...
https://english.stackexchange.com/questions/58009/most-impor…
travel_explore
web search NEUTRAL — I've recently come across a novel called A most wanted man, after which being curious I found a TV episode called A most unusual camera. Could someone shed some light on how to use "a most" and wh...
https://english.stackexchange.com/questions/85112/how-when-d…
travel_explore
web search NEUTRAL — Most is what is called a determiner. A determiner is "a word, such as a number, article, personal pronoun, that determines (limits) the meaning of a noun phrase." Some determiners can only be used wit…
https://english.stackexchange.com/questions/93304/most-is-vs…
info Disclaimer: This analysis is generated by AI and should be used as a starting point for critical thinking, not as definitive truth. Claims are verified against publicly available sources. Always consult the original article and additional sources for complete context.