As a zoologist focusing on the studies of apes and monkeys, I've been studying why humans evolved to become the naked ape and why skin comes in so many different shades around the world.

But compared with apes and monkeys, we have very little.

A team of researchers trained three rhesus monkeys to associate 26 clearly different symbols consisting of numbers and selective letters with 0-25 drops of water or juice as a reward.

After running hundreds of tests, the researchers noted that the monkeys would go for the higher values more than half the time, indicating that they were performing a calculation, not just memorizing the value of each combination.

Along the way are tales of kings and queens, hot air balloons...and monkeys in space.

Here's how Harvard Medical School scientist Margaret Livingstone, who led the team, described the experiment: in their cages the monkeys were provided with touch screens.

How did the monkeys get their reward in the experiment?

If the monkeys touched the left side of the screen they would be rewarded with seven drops of water or juice; if they went for the circle, they would be rewarded with the sum of the numbers—17 in this example.

I'm a scientist who studies animals such as apes and monkeys.

Monkeys seem to have a way with numbers.

The researchers then tested how the monkeys combined—or added—the symbols to get the reward.

The under-estimation was systematic: when adding two numbers, the monkeys always paid attention to the larger of the two, and then added only a fraction of the smaller number to it.