Nice little thing in gmail

I accidentally discovered that by clicking on the text of the letter the right button and, without releasing, by moving the mouse to the left / right, you can go to the previous / next letter. Accordingly, moving the mouse up - you return to the list of letters.
Actually, in the list of letters, too, a similar number rolls ...

UPD alive prompted that this is a feature from Labs - Mouse gestures.
I thought - the standard behavior.