1. We humans have the ability to learn, to reason and solve problems. We're self-aware, and we’re also conscious of the presence, thoughts and feelings of others. We make tools and practice the art of deception. We're creative. We think abstractly. We have language and use it to express complex ideas. All of these are arguably signs of intelligence. Scientists may not agree on the best and fullest definition of intelligence – but they generally agree that humans are highly intelligent.
2. Chimpanzees-If we humans possess intelligence, chimpanzees must have some as well: Our genomes are at least 98 percent identical.
3. Dolphin - in Australia a dolphin uses a sponge to protect her snout when foraging on the seafloor, a tool use behavior that is passed on from mother to daughter. Scientists say that’s just one sign of dolphin smarts.
4. Elephants - The sheer size of their brains suggests that elephants must know a thing or two about the ways of the world.
5. Cephalopods - (octopi, squid, cuttlefish) The cephalopod brain surrounds the esophagus, but shares with the human brain features of complexity such as folded lobes and distinct regions for processing visual and tactile information. The how-smart debate swirls around deciphering observations that the creatures have a seemingly irrepressible curiosity, a disdain for boredom, an ability to learn and the capacity to use tools.
6. Crows - They are crafty critters. They fashion tools from twigs, feathers and other bits of debris to snare food from hard-to-reach places.
7. Squirrels - Researchers recently reported that the rodents put on elaborate shows of deceptive caching to thwart would-be thieves. The behavior increased in a lab experiment after squirrels observed humans stealing their peanuts.
8. Dogs - They can learn to sit, lie down and fetch, for example, but can they read their owner's intentions? Research suggests they can at least find food in response to non-verbal cues, a type of understanding that scientists think may be akin to the human ability to understand someone else's point of view.
9. Cats - Like dog owners, some cat owners have trained their pets to sit down, roll over and jump through hoops. Cats learn the tricks by observation and imitation, egged on with positive reinforcement.
10. Pigs - They are perhaps the smartest, cleanest domestic animals known – more so than cats and dogs, according to some experts. But pigs don't have sweat glands, so they roll around in the mud to stay cool. A sign of their cleverness came from experiments in the 1990s. Pigs were trained to move a cursor on a video screen with their snouts and used the cursor to distinguish between scribbles they knew and those they were seeing for the first time. They learned the task as quickly as chimpanzees.