Scientists Thought Only Great Apes Were This Smart, But a Tiny Fish Proved Them Wrong

The post Scientists thought only great apes were so intelligent, but a small fish proves them wrong appeared first on AZ Animals.

Quick shot

• Cleaning wrasse Use a mirror to locate and scratch marks on the body.

• Experiments have shown that fish can link reflexes to sensations in their own bodies.

• The findings challenge the assumption that only brained animals can recognize themselves in a mirror.

• Research raises questions about animal intelligence and how scientists interpret mirror tests.

For decades, scientists have used mirror experiments to explore whether animals can recognize themselves. In that test, researchers placed a mark on the animal’s body that could only be seen in a mirror. If animals use mirrors to see markings on themselves, scientists would interpret this behavior as self-recognition. Only a small number of species seem to pass the test. These include great apes, dolphins, elephants and some birds.

New experiments on small reef fish complicate the situation. Researchers studying the blue-striped wrasse have found that the species can use mirrors to locate marks placed on its body. When the fish sees the reflection, it scratches at the marked spot. When the mirror was removed, the scratching stopped. These observations suggest that fish use mirrors to guide their actions.

The results sparked debate among scientists. Some believe the fish exhibits a form of self-related awareness. Others think the fish simply learned to associate the reflex with sensations on their skin. Regardless, these findings are prompting researchers to reconsider how to interpret the mirror test.

a reef fish known for cleaning other animals

Blue-striped wrasse live on coral reefs in the Indian and Pacific Oceans and play an unusual ecological role. Rather than hunting typical prey, it removes parasites and dead tissue from larger fish. Many coral reef species visit cleaning stations where wrasse perform this service. Its body is slender, usually only a few inches long. A dark stripe runs from nose to tail along a light background. Other fish will usually recognize this pattern and approach the wrasse without fear.

Because the wrasse regularly checks the bodies of other fish for tiny parasites, it has keen visual abilities and a keen interest in small marks or spots. These characteristics make it an attractive candidate for the mirror self-recognition test. Scientists suspect the species may be reacting strongly to the unusual markings on its body. The researchers reasoned that if there were any fish willing to examine the tiny spots on its skin, the wrasse would likely be one of them.

Original Mirror Self-Identification Test

Psychologist Gordon Gallup Jr. developed the Mirror Self-Identification Test in the early 1970s. The experiment was designed to determine whether animals can recognize their own reflections. In a typical setup, animals first become familiar with a mirror placed in their environment.

After this period, the researchers added colored markers to parts of the animal’s body that were not directly visible. Mirrors become the only way for animals to observe markings. Scientists consider the test passed if the animal touches, rubs or studies the markings on its own body after looking at the reflection.

Humans begin to pass the mirror test at approximately 18 to 24 months of age. For years, researchers thought only a few animals possessed this ability. Apes, dolphins, elephants and magpies are the most obvious examples.

This has led some scientists to believe that the test measures a deep sense of self. According to this view, species that pass the test possess advanced cognitive abilities, while those that fail lack this level of understanding.

Fish meets mirror in laboratory

The researchers later decided to study how cleaner wrasse reacted to mirrors placed inside the aquarium. At first, the fish reacted violently, viewing the reflection as a rival intruder. This behavior is similar to the territorial response of many species.

After repeated exposure, their behavior changed. Instead of attacking the mirror, the fish started making unusual movements in front of the mirror. They squirmed and paused, as if examining their appearance.

The scientists then smeared a small brown mark that resembled a parasite on the fish’s throat. While the mirror was still in place, some people used their throats to scrape the tank floor or nearby surfaces. This behavior is closely related to the way the wrasse remove parasites during the cleaning process. When the mark is not visible or the mirror is not present, the scratching behavior essentially disappears. These results indicate that fish use mirrors to detect and respond to marks.

Reverse the order of experiments

Some scientists believe that early tests may not prove self-awareness. Critics believe the fish could simply interpret the reflection as another fish carrying a parasite. This interpretation triggers a cleansing response rather than self-directed awareness. To test this possibility, the researchers designed a new version of the experiment. Instead of introducing the mirror first, they painted the marks on the fish before the mirror appeared. Therefore, the fish senses the mark but cannot see it.

When the mirror was finally introduced, within about an hour many fish began scraping over the marked area. In earlier experiments, it took fish several days to reach this stage. The faster response indicates that the fish quickly associate the reflex with the abnormal sensation on their body. Some also perform something similar to emergency testing. They move their bodies in unusual ways while observing their reflections. In some cases, they placed pieces of food in front of a mirror and observed the reflection’s reaction. These behaviors are similar to those of other animals that explore how reflexes correspond to their own movements.

Explain what the mirror test measures

Passing the mirror test does not necessarily prove that animals have the same self-awareness as humans. The experiment measures whether animals can use reflex visual feedback to guide behavior directed toward their own bodies.

Some scientists have suggested that animals may achieve success by learning connections between movement, visual cues and body sensations. In this explanation, animals recognize patterns that link their behavior to mirror images. Others believe that this behavior indicates a more advanced form of self-related processing. Fish may retain mental representations of their bodies and compare what they see with what they feel.

Evidence from other experiments has heightened interest in this question. Wrasses have shown the ability to adapt their behavior to body size and environmental openings. Some studies show that they respond differently to images that resemble themselves compared to other fish. The findings suggest the species may possess cognitive abilities that researchers had not thought of in small fish.

Early species that passed the test

Until studies are conducted on wrasse, the list of species that have passed the mirror test remains limited. Chimpanzees and orangutans use mirrors to examine markings on their faces or heads. Some people touched the marks and then examined their fingers.

Bottlenose dolphins display similar behavior in aquatic environments. They twist their bodies to see the markings on the side while facing the reflective surface. Asian elephants also show a response of recognition of their bodies. Some birds have produced positive results under controlled conditions. Eurasian magpies, for example, leave scratches on their feathers after seeing themselves in a mirror. These species all have large brains and complex social structures. Their success led researchers to hypothesize that advanced cognition evolved primarily in large mammals and a few birds. The wrasse experiment challenges this assumption by demonstrating that small fish can exhibit similar behavior.

Expand ideas about animal intelligence

Research on many species has begun to change the way scientists think about intelligence. Cognitive skills once thought to be rare now appear in a wide variety of animals. Crows solve multi-step problems and use tools. Octopuses can navigate complex environments and manipulate objects. Bees can learn patterns and rules in training experiments. Some insects appear to be able to count small amounts when searching for food sources. Each of these findings suggests that cognitive abilities may have arisen through different evolutionary pathways.

Wrasses provide another example. Its daily life requires careful observation of other fish, precise movements near large predators, and quick decisions during cleaning interactions. These challenges may have encouraged the development of flexible problem-solving skills. Rather than viewing intelligence as a complex ladder, researchers are increasingly considering the many forms of cognition shaped by each species’ environment and behavior.

Impact on animal welfare and research

Evidence that fish may possess advanced cognitive abilities has sparked debate about animal welfare. Wrasses are sometimes collected for use in aquariums or for parasite control in fish farms. A better understanding of their behavior may influence how they are placed and handled. Providing an appropriate environment can improve the welfare of animals in captivity.

The findings also encourage scientists to design experiments tailored to each species’ natural capabilities. Traditional tests developed for primates may overlook important forms of intelligence in animals with different senses or lifestyles. Studying cognition in multiple species helps researchers gain a more complete understanding of how the mind evolved. It also reveals that complex behaviors can occur in animals with very different brain structures.

The little fish that sparked scientific debate

The blue-striped cleaner wrasse does not attract attention because of its size or appearance. Instead, its daily work clearing parasites from other fish has put it at the center of major scientific discussions. Rather than providing a simple answer, these experiments highlight the complexity of animal behavior. Different species may arrive at similar solutions via very different biological pathways. The wrasse continue to serve as a reminder that scientific assumptions sometimes change when researchers look at familiar animals in a new light.

The post Scientists thought only great apes were so intelligent, but a small fish proves them wrong appeared first on AZ Animals.