47 milliseconds is a very small time period in terms of human reaction speed. It is comparable to the time it takes the signal to travel from the brain to the muscles via nerve fibers. There’s a term in medicine that sounds like “the time of a simple sensorimotor response”. It is the time between an occurrence of some event the brain can easily process (for example, the lighting of a bulb) and a muscle reaction (a press on a button). For humans, this time is 200-250 milliseconds on average. During this time the eye registers the event and transfers information about it into the brain, the brain then identifies the event and sends an appropriate command to the muscles. A lag of 47 milliseconds doesn’t seem big in comparison with this number.
It’s impossible to notice this lag at everyday office work. You can try to catch the difference between the movements of the mouse on the desk and the movements of its pointer on the screen, but the time the brain takes to process these events and relate them to each other (note also that the watching of the movements of the pointer is a much more complex task than the watching for a bulb to light up as in the simple sensorimotor response test – and the reaction time is going to be longer) is so high that 47 milliseconds prove to be an insignificant value.
However, many users report that they feel the mouse pointer moves slowly on their new monitor. They also find it difficult to hit small buttons and icons at first attempt as they always used to do. And they put the blame on the input lag that was missing in the older monitor and is present in the new one.
But when you come to think of it, many people are now transitioning to new large models from either 19” models with 1280x1024 resolution or from CRT monitors. Let’s take a transition from a 19” LCD to the above-mentioned 215TW: the horizontal resolution has increased by a third (from 1280 to 1680 pixels), which means you have to shift your mouse farther to move its pointer from one edge of the screen to another – if the mouse settings have remained the same. That’s where the feeling of “slow pointer” comes from. You can get the same feeling on your current monitor by lowering the pointer speed in three times in the mouse driver’s settings.
It’s the same with the failure to hit the buttons on the new monitor. Our nervous system is too slow to catch the pointer-above-the-button moment with the eyes and transfer a nervous impulse to the finger that presses on the mouse’s left button before the pointer leaves the button. So, the accuracy of hitting the buttons is in fact reduced to a repetition of learned movements when the brain knows beforehand what movement of the hand corresponds to a specific movement of the pointer and with what delay the command to the finger should be sent so that the pointer was exactly above the necessary button when the finger presses the mouse. Of course, all these learned actions become useless when the resolution and the physical size of the screen change. The brain has to adjust itself to the new conditions and you’ll be indeed missing the onscreen buttons for a while until this adjustment is accomplished. But this is in no way related to the monitor’s input lag. Just like in the previous experiment, you can achieve the same effect by changing the sensitivity of your mouse. If you increase it, you’ll be racing past the necessary button. And if you decrease it, you’ll be stopping your pointer before reaching it. But the brain will adapt after a while, and you’ll again be hitting the buttons with ease.