Octopuses are smarter than we thought. A mounting pile of evidence suggests that the eight-armed sea creatures exhibit a number of "human-like" tendencies that put them on the same intellectual plane as the wilier house pets. Here's why scientists have new respect for invertebrate cephalopods:

What "human-like" tendencies have been exhibited?
One octopus in captivity was observed "cleaning the front of its den" after securing food, then carefully arranging rocks to cover the entrance before going to sleep. Such an endeavor requires "foresight, planning," and "even tool use," says Sy Montgomery at Orion Magazine. In another study, octopuses "learned to open childproof caps on Extra Strength Tylenol Pill bottles — a feat that eludes many humans."

Hmm. What else?
One female octopus was observed "blowing carefully modulated jets of water from her funnel to send [a pill bottle] to the other end of her aquarium, where the water flow sent it back to her. She repeated the action 20 times," Montgomery reports. One excited researcher quickly got on the phone to call her colleague: "She's bouncing the ball!"

How about their memories?
Octopuses can remember humans, says Josh Rothman at the Boston Globe, and "have particular human friends and nemeses." The animals recognize their own names when called out, crawling affectionately towards caretakers they like. If an octopus isn't enamored of you, he'll squirt water at you when you call.

So they must have big brains, right?
Nope. Most octopuses kept in aquariums have only walnut-sized brains, on par with the gray matter of talking parrots. What's "weird," says Montgomery, is the distribution of the octopus' neuron count. While the creatures only boast about 130 million neurons (humans have 100 billion), three-fifths of an octopus' brain cells aren't even in its head — they're in its arms, as if each tentacle has "a mind of its own," allowing it to feel out environments in a way researchers are still trying to understand.

How did the animal get so smart?
Scientists think the loss of the ancestral shell eventually sharpened the animals' wits. Though the modern octopus' lack of a shell leaves him more mobile for hunting, it also leaves him vulnerable to bigger predators. "Only the smartest octopuses would survive — the ones who could hide the most cunningly, traveling alone to avoid exposure," says Annalee Newitz at io9. It's why the animals "use tools to hide all the time."

Source: Boston, io9, Orion Magazine