This online activity lets learners explore how computer programs called "CAPTCHAS" work to test whether you are a human or a computer. Learners will be tested with a series of visual activities to identify letters and words that have been changed or distorted to make them hard to read. These tests explore how you read letters versus how a computer reads them. The activity also explores human vision and how human brains use "pattern recognition" to help us understand what we see. Finally, this activity gives learners an introduction to the history of computer intelligence and of the "Turing Test" developed by Alan Turing in his 1950 paper, "Computing Machinery and Intelligence."