Like their human counterparts, chimp test takers appear to know when they get a question right. And they seem to know when they've botched it, too, researchers said in a new study published in the journal Cognition.
That may seem novel, but it shows that our primate cousins probably share with us a level of thinking known as metacognition.
It's more than just knowing something. Metacognition is knowing that you know something. Like humans, chimps can think about their thinking and change their behavior as a result, the researchers believe.
They had suspected as much, so they devised an experiment to check it out. They gave three chimps computerized memory tests and rewarded them with food for correct answers, but they built in some hitches to tease out signs of metacognition.
The reward appeared at a place away from the test area, and when the chimps got an answer right, a sound alerted them that the food was going to appear -- with a slight delay -- at the distant spot. They had to hustle to get to the other station before the food popped out, or it would disappear, or go down the drain, so to speak.
But that alerting sound was delayed, too. The apes barely had enough of a heads up to make it to the reward station in time to catch the food before it vanished.
After a while, the chimps appeared to get a sense for when they got an answer right and when they didn't. And when they did, they often darted for the food station ahead of that tardy sound signal.
If the monkeys got an answer wrong, more often than not, they sat things out. After all, when you've bombed, why go to the trouble?
"These untrained, spontaneous confidence judgments demonstrated that chimpanzees monitored their own states of knowing and not knowing and adjusted their behavior accordingly," said the study, which was conducted by researchers at universities in Georgia, South Carolina and New York.
But that doesn't mean that they are having the same experience of consciousness as humans do when they experience metacognition, the scientists cautioned.
Crows seeing spots
When crows are hunted, they may know how many are out to get them, German researchers say.
Old hunters' tales say that crows can count. If they see three hunters hide in the woods, they'll stay out of reach until the last one has left -- even if the hunters go gradually, one by one.
There's truth to those tales, researchers at the University of Tuebingen in Germany say in a new study
. Crows can recognize numbers of things, and the skill is hardwired into the birds' brains, they say.
The scientists trained crows to recognize groups of dots. Then they changed the sizes of the dots, and their arrangements, and the birds still recognized the number.
The researchers observed an area of the brain that took in visual stimuli and noticed that the neurons there did not register the size, shape or arrangement, but just the number of dots.
"When a crow sees three points, seeds or even hunters, single nerve cells recognize the 'threeness' of the objects," said neuroscientist Helen Ditz.
Primate brains do it the same way, the scientists said, which is surprising, given how different they are from, well, bird brains.