Single taps on the touchscreen act as left - button clicks while a longer press works like a right mouse button click. (trustedreviews.com)
Then came the tricky part: in the middle of the task, researchers told the participants to now click the left mouse button for a different letter combination. (sciencedaily.com)
But along with the scroll wheel, left and right - click mouse buttons, there's an additional center button — or far - right, depending on your perspective. (digitaltrends.com)