Guppies can be fooled by optical illusions into believing objects are smaller or larger than they really are. This suggests they might not always make the best choices in their natural environment.

Prefer Newsweek on Google to see more of our trusted coverage when you search. How people respond to stressful situations can say a lot about their personalities—and it turns out the same is true of a ...

NEWPORT NEWS, VA.? There’s no coat to brush and fluff. No nails to clip, or teeth to brush. Forget obedience training because they don’t respond to verbal commands. A Half Black AOC male guppy is ...

When Robert Heathcote dips his head into the rivers of Trinidad, he’ll often see little black dots moving through the water, even when it’s murky. Those dots are the eyes of small, inch-long fish ...

Tiny guppy fish change their eye colour to warn off rivals, new research shows. When facing an opponent, Trinidadian guppies rapidly turn their irises from silver to black before attacking their ...

Bringing a fish home for your child might sound like a small decision, but it’s actually a big step into responsibility, bonding, and joy. Among the most popular pet fish, goldfish and guppies top the ...

A large group of yellowfin tuna swimming off the coast of Italy. Like all fish, they sleep, but it's not like human sleep. Giordano Cipriani/The Image Bank via Getty Images From the goldfish in your ...