Smell Of Fish Makes People Think More Critically

By on June 5, 2023
Dead fish float on the shoreline of Mona Lake along Wellesley Drive just east of Ross Park in Norton Shores Wednesday. Date shot: 4/2/08. Dead fish float on the shoreline of Mona Lake along Wellesley Drive just east of Ross Park in Norton Shores Wednesday. Date shot: 4/2/08. (Credit: Gerald Simmons via Flickr CC BY-NC-SA 2.0)

When someone says that something smells fishy, the meaning is obvious for English speakers; something isn’t right. However, fish-related idioms appear to be common throughout the world, as the smell of fish seems to be associated with untrustworthiness in many cultures. There are analogs of the “something smells fishy” phrase in more than 20 languages worldwide.

Why Do Fish Smell?

First, it may be helpful to know why fish smell and why some fish are particularly pungent. reports that the fishy odor often thought of is a result of natural decay in fish. Amino acids are frequently touted in health circles as being a necessary part of a sustainable and nourishing diet—in fish, they are no less essential. Fish cells are filled with amino acids and amines to help keep the fish alive in saltwater. The

Ocean fish typically rely on Trimethylamine oxide (TMAO), which inevitably transforms into trimethylamine (TMA) when the fish begins to break down. TMA is typically the compound associated with that well-known fishy odor. The American Society for Nutrition explains, “Freshwater fish generally do not accumulate TMAO because their environment is less salty than their cells.” This means that freshwater fish typically don’t take on that fishy odor.

Why We Say Something’s Fishy

Across languages, there are often very few similarities between expressions, so the consistent ties to fish couldn’t be only coincidence. In 2015, researchers at the University of Michigan and the University of Southern California made the find by studying the responses of undergraduate students to questions when the smell of fish oil was present or absent.

The fish oil notably made people more suspicious, meaning that they were more capable of identifying and responding to trick questions when asked. The question students were asked is often called the Moses Illusion, a trick question containing purposefully misleading information.

The question was, “How many animals of each kind did Moses take on the Ark?”

Anyone familiar with the biblical story of Noah and the Ark can easily identify the error in that question—if they’re paying attention. If distracted or thinking about the questions uncritically, it’s easy for the trick to fly under your nose. The control group was comprised of 30 students who were not exposed to the fish oil, and of that group, 84 percent failed to answer the question correctly.

By comparison, the group who were asked the question with the fish oil present were much more accurate–42 percent of the experimental group noticed the misleading information. Scientists believe that the smell of fish makes people more skeptical, which could increase the motivation to think things through.

“If I’m distrustful, then I’m thinking, ‘Something’s wrong here.’ And then I have to think more critically and figure out what is wrong,” said Norbert Schwarz, the study’s lead author and provost professor of psychology and marketing at USC, in a release.


Beyond the smell of fish, scientists say that the smell of rotting food, in general, can cause skepticism. Scientists involved in the study theorize that the suspicion caused by the smell of fish may be different for other countries. “We are looking at collaborating with researchers in other countries to learn more about the role of sensory experience in critical thinking,” said Schwarz, in the statement.

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