Trying to objectively test intelligence in any animal species is going to be a challenge, but doing it for fish seems almost impossible. How can you possibly measure the intelligence level of creatures who think and behave so differently from us? As it turns out, researchers have actually uncovered several reliable ways to gauge the intelligence level of different fish species.
Let’s break down the key methods scientists use to test and research the cognitive abilities of their fish subjects!
Measuring Social Intelligence in Fish
Most fish species rely heavily on some level of social cooperation and communication to survive. And, because of this, researchers can often get a broad idea of the intelligence of marine animals and fish by testing their social abilities. Luckily, there are quite a few effective methods for doing just that.
One test involves simple recognition. Scientists can test individual fish to see if they show signs of recognizing familiar fish in their tank. This can be an effective proxy for cooperative intelligence, especially in the most social fish species like guppies and zebrafish.
Another way researchers measure a fish species’ social intelligence is by conducting teamwork tests. For example, many fish will cooperate and take turns looking out for predators. Some studies have even shown that certain fish can remember individuals who don’t cooperate and refuse to work with them in the future.
What Is the Mirror Test?
The mirror test is one of the most famous and noteworthy experiments for pinpointing animal intelligence. Though the test was originally used by Gordon Gallup to test chimpanzee self-awareness, it’s been expanded for use in many other creatures, including fish. The basic premise of the experiment is that an animal is placed in front of a mirror. Researchers then carefully assess signs of whether or not the subject recognizes its own reflection. Theoretically, recognition should indicate some degree of self-awareness in the creature.
A huge breakthrough in the mirror test came when wrasses were put through the experiment. Researchers found that the wrasses showed clear signs of recognizing their own reflections on a substrate. While this test was only conducted on one species of fish, it still indicates promising potential for self-awareness in other more popular pet fish species like neon and Congo tetras.
Aquarium Mazes and Fish Navigation
Navigational abilities play a gigantic role in the survival of most fish species. So, the relative intelligence of many fish can be judged to a large degree by how well they’re able to navigate an aquatic environment. Aquarium maze tests and test routes are one of the best ways for researchers to measure this ability.
One of the most intriguing examples here is goldfish. Studies have shown that goldfish navigate fish tanks with remarkable accuracy. Scientists have found that their goldfish test subjects were able to form mental maps of an aquarium test route. The goldfish in these tests also adapted surprisingly well to novel stimuli and were still able to navigate routes when their fish tank’s backgrounds were changed. Adapting to changing environmental circumstances is a cornerstone of how we define animal intelligence.
Likewise, some types of fish hide in a tank when they sense danger or potential predators nearby. This natural ability to quickly locate good hiding spots, even in unfamiliar aquariums, points to strong spatial intelligence. Species that show particularly adept skills in this regard include Clown and Zebra pleco, along with Banjo Catfish. It turns out cats aren’t the only animals who can be sneaky when they want!
Fish Intelligence and Operant Conditioning
Operant conditioning is a classic animal training method, and one that often correlates with a species’ overall level of intelligence. Dogs, for example, often excel at operant conditioning training methods. The core theoretical basis of the method is that intelligent animals will repeat behaviors that result in positive stimulus, and avoid behaviors that provoke negative stimulus.
So, do fish show impressive responses to operant conditioning techniques? Absolutely! One study of zebrafish found that the test subjects were able to discriminate between numbers after operant conditioning.
After being consistently rewarded with food, zebrafish in the study could identify the difference between 4 and 5 items. Basically, the fish were given food when they correctly chose the right number of items. Some were trained to select the larger number, and others the smaller number. Interestingly, the zebrafish actually showed higher number discrimination abilities than many mammals, including dogs!
How Do Memory Tests Work for Fish?
Memory is an essential component of most forms of animal intelligence, and this applies just as much to fish. But how can researchers effectively test the memory of different fish species? Usually, it comes down to similar techniques scientists use to measure memory in dogs, cats, and other animal species.
One frequent fish memory test is to introduce novel objects, remove them, and then see if the fish remembers the object when it’s reintroduced. Many fish perform better than you might expect on this metric. Goldfish, in particular, have a much longer memory than the common 10-second myth.
Mazes are also used to test both memory and problem-solving abilities in fish species. Researchers often test fish to see if they remember how to navigate old mazes that they’ve solved before. This is actually very similar to canine navigation training, where guide dog breeds such as Golden Retrievers are taught to navigate public streets and walkways.
