Something’s literally fishy: Study finds fish smell makes us suspicious

A nose-wrinkling fishy smell stops us from eating something unsafe and getting sick, and it helps us avoid trouble because it raises our suspicion. Researchers have found another benefit: It can boost critical thinking.

Scientists think our tendency to respond to fishy smells with suspicion is an evolved mechanism that helped our species survive centuries. It’s a widely-accepted metaphor, appearing in more than 20 languages worldwide, and our typical to the stench of fish – suspicion – has its drawbacks. Prior studies have found our suspicion, as a reaction, can undermine trust in other people or resources.

However, such mechanisms also can support our reason and judgment. Norbert Schwarz, a USC Provost Professor of psychology and marketing at the USC Dornsife College of Letters, Arts and Sciences and Marshall School of Business, likes to discover those benefits through experimentation.

In this latest study of metaphor and reasoning, Schwarz and researchers David Lee and Eunjung Kim from theUniversity of Michigan decided to further test our response to fishy smells. They found that whenever we catch the slightest whiff, we are more likely to second-guess misleading information and scrutinize it instead of overlooking, accepting or ignoring it.

“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 Schwarz, the study’s lead author who co-directs the Dornsife Center for Mind and Society.

A red herring

Researchers conducted reasoning experiments to test their suspicion. For one, they asked 31 students to complete a questionnaire in a booth that smelled slightly fishy because the researchers had, unbeknownst to the students, sprayed it with some fish oil. Separately, 30 other students completed their questionnaires in a fishy-free booth.

Among the various questions was a red herring that scientists call the “Moses Illusion”: “How many animals of each kind did Moses take on the Ark?”

Repeated tests have shown people fail to notice that the Moses Illusion contains misinformation, even if during an experiment, they are forewarned of a potential distortion. Participants consistently answer “two” to this question, even when they know that Noah, not Moses, built the Ark and ferried pairs of animals to safety.

In this latest study, a spritz of fish oil in one booth helped many participants recognize the misinformation.

In the fishy booth, 13 of 31 students — 42 percent — detected something amiss with the Moses question. These skeptics responded that they “can’t say” how many animals Moses had taken.

By contrast, their peers in the non-fishy booth were more trusting: Only five of those 30 students – 17 percent – noticed the distortion.

Follow your nose

In effect, the study confirmed the old adage, “The nose knows,” and knowing can help us raise a stink about misinformation. Schwarz said he hopes to further explore the fishy smells metaphor and its influence on reasoning.

The smells that trigger suspicion vary from country to country, although it always is generated by rotting food or organic matter, Schwarz said. However, in some countries, the smell of suspicion is not the smell of fish, but could be, for example, a rotten potato. “We are looking at collaborating with researchers in other countries to learn more about the role of sensory experience in critical thinking,” he said. The study was published this month in the Journal of Experimental Social Psychology.

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