Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: What does the button below the scroll wheel do? Is it reprogrammable? Also, is hyper-scrolling activated by pressing down on the scroll wheel?
Document: It does trade the search button next to the left button for a 'hidden' button activated by pressing the thumbrest, and the click/hyper scroll switch is now on the top. Oh, and it's on Logitech's Unifying system, unlike the dedicated receiver just for the MX620. If I get as many years out of this as I got out of the MX620, I'll be quite happy.
it tracks beautifully and feels like I had hoped it would.the scroll wheel is another awesome little feature, by pressing the button directly behind it you can switch between a free-wheel scrolling (no clicks) which is great for long documents and pages that support smooth scrolling or you can switch it to click scrolling (where it clicks forward by precise increments) which is great for games and for when you want to scroll a little more precisely.
Nice mouse however 4 stars because you don't really feel like you are pressing buttons and the scroll is so slick however there a button under the scroll wheel press it you can hear it scroll press again it is slick as butter. This helps with it being too slick.Unifly software issue easy to fix what you need to do is go into advance and unpair device then the software will find and work as design. Also you must download the setpoint software if you want to change features or see battery life etc.
It is a little hyper sensitive depending on which program your are using (Chrome, OneNote, Outlook, etc). Luckily the Logitech software lets you adjust this feature pretty well and there is also an easy to hit toggle switch button below the wheel that lets you go back to the traditional wheel scrolling behavior. So this is not an issue for me, I just toggle between the modes depending on which program I'm using.
The size is too small for my hands, but it's great for traveling. It's larger than most portable mice on the market. The button configuration is great and the options to assign them is good. The scroll wheel can go in 4 directions which is amazing, but isn't necessary for web browsing but good for gaming and work. The wheel itself has 2 features, Hyper-fast scrolling which it is exactly that, uber fast! But I love you can switch between that and the old fashion ratchet wheel.
the scroll wheel is wobbly by a little so if it shakes youll hear it move around but nothing to be downed upon. the scroll wheel is also loose even without the scroll wheel turn on hyper scroll but you can at least hear the clicks. the 3rd thumb button (hidden one) cant be used in some games which is dissapointing. great mouse overall
This mouse is still using older laser tracking rather then its newer Darkfield technology that is found on the Performance MX mouse which I also own and LOVE. This mouse has all the usual features like hyper scrolling, horizontal scrolling, Fwd/Bkd thumb buttons, app switch button and 2.4 ghz receiver. I think its great for laptops or for people with smaller hands.
The scrolling wheel its also very cool! you got two modes, one for slow scrolling and one for hyper fast scrolling... both works perfect.. So yes! DEFINETELY BUY THIS ONE!
This mouse has a dual-mode scroll wheel (which I had come to regard as a necessity), although the materials are a little cheaper and it is now activated by a button directly behind it. Logitech claims the older design (toggling between the 2 modes via a press on the wheel itself) was confusing to users -- whatever. The ergonomics are close to the MX-R, as it the weight.
Also, in order to actually program that button itself, you have to manually download Logitech SetPoint software, which is a hefty 80MB in size. With the free scrolling mouse, you can actually remove the friction of the mouse wheel where it would scroll one click at a time. Rather, you're now able to spin the wheel and it would continuously spin without any friction stopping it.
Answer: The button below the wheel toggles the wheel between "smooth" scrolling and "notched" scrolling. It's mechanical and is not usable as a button for computer input.