"But moving just the forefinger — not the whole hand, or bunching all the fingers, but just the forefinger — actually makes the mouse rotate, particularly for l

"But moving just the forefinger — not the whole hand, or bunching all the fingers, but just the forefinger — actually makes the mouse rotate, particularly for left- and rightward movements. If the sensor is up the front of the mouse, that rotation of the mouse will give the user the desired outcome: the cursor will accurately move to the left or right, or back and forth. But if the sensor is in the middle of the mouse, then all of that fine control is lost: no or little movement will be registered." Paraphrased: With the ball/sensor at the top of the mouse, you can have more horizontal control by rotating the mouse left or right. My response: With the way that the hand rotates (the base of the hand as a fixed point), the speed of the cursor slows down the farther back the sensor is placed. So in essence, you can get more precise horizontal control with our current sensor placement standard than with a index-thumb sensor. This is good because it's easier for the human arm to move the mouse quickly horizontally by rotating at the elbow than it is to move vertically (by rotating the shoulder, or in my case, moving my wrist/fingers). Then again, I have my mouse set pretty sensitively, so I can traverse the entire screen within the range motion my wrist allows (no need to lift my hand at all). Also, I'm pretty sure that the difference is negligible compared to sensitivity settings and advances in technology (such as slowing the cursor when the mouse is moved slower... that sounds obvious, how about decreasing the absolute speed of the cursor when the mouse is moved slower).