How Does the Fortune Teller Miracle Fish Work?

Learn the Science behind the fortune-telling fish

Fortune Teller Miracle Fish
This is a Fortune Teller Miracle Fish and its packaging. If you place the Fortune Teller Miracle Fish in your hand it will bend and wiggle. Decipher the movements to predict your future. Todd Helmenstine

If you place the plastic Fortune Teller Miracle Fish in your hand it will bend and wiggle. You can reportedly decipher the movements of the fish to predict your future. But those movements—though they may seem miraculous—are a result of the chemical composition of the fish. Read on to find out how the fish works as well as the science and engineering behind this fortune-telling device.

Children's Toy

The Fortune Teller Miracle Fish is a novelty item or children's toy.

It is a small red plastic fish that will move when you place it in your hand. Can you use the movements of the toy to predict your future? Well, you can, but expect about the same level of success as you would get from a fortune cookie. It doesn’t matter, though, because the toy is great fun.

According to the company that manufactures the fish—which appropriately is called Fortune Teller Fish—the fish's movements describe specific emotions, moods, and temperament of the person holding the fish. A moving head means the fish-holder is the jealous type, while a motionless fish indicates that the person is a "dead one." Curling sides mean that the person is fickle, but if the fish curls up entirely, the holder is passionate.

If the fish turns over, the holder is "false," but if its tail moves, she is an indifferent type. And a moving head and tail? Well, watch out because that person is in love.

The Science Behind the Fish

The Fortune Teller Fish is made of the same chemical used in disposable diaperssodium polyacrylate. This special salt will grab onto any water molecules that it touches, changing the shape of the molecule. As the molecules change shape, so does the shape of the fish. If you submerge the fish in water, it won't be able to bend when you place it on your hand.

If you let the fortune teller fish dry out, it will be good as new.

Steve Spangler Science describes the process in a bit more detail:

"The fish grabs onto the moisture on the surface of your palm, and since the palms of human hands have a lot of sweat glands, the plastic (fish) is immediately bonded to moisture. The key is, however, that the plastic grabs water molecules only on the side in direct contact with skin"

However, says Steve Spangler who operates the website, the plastic doesn’t absorb water molecules, it merely grabs them. As a result, the moist side expands but the dry side remains unchanged. 

Educational Tool

Science teachers commonly hand out these fish to students and ask them to explain how they work. Students can propose a hypothesis to describe how the fortune-telling fish works and then design an experiment to test the hypothesis. Usually, students think the fish may move in response to body heat or electricity or by absorbing chemicals from the skin (such as salt, oil, or water).

Spangler says you can extend the science lesson by having students place the fish on different parts of their bodies, such as the forehead, hands, arms, and even feet, to see if the sweat glands in those areas produce different results.

 Students can even test other, nonhuman objects to see if the fish reacts—and predicts the moods and emotions of a desk, countertop or even a pencil sharpener.