This article was originally posted on RealClearScience.

It has been long thought that one of the characteristics that makes humans unique is our ability to learn and manipulate symbols for communication. However, this notion is starting to slowly unravel. Koko the gorilla knows sign language, and Alex the parrot was probably the most well-spoken bird to have ever existed. Also, a chimpanzee was trained to use Arabic symbols to add up sums as large as 4, and monkeys were taught to add dots together. Continue reading →