How long does it take for you to react? Take the following test, and see how long it takes for the light of the background color to reach your eyes, your eyes to send the visual information to your brain, your brain to process what response is appropriate, and the signal from your brain (via synapses) to reach your finger. Do you react differently to different colors?
Click on "start," wait until the page color changes, then hit "stop"
For the sake of browser compatibility and testing experiments, there are 2 different "Start/Stop" methods: if the buttons don't work, try the text links. This test requires a fairly recent browser, with javascript enabled.