It's not s stupid question by any means...there have been questions about the magic mouse recently, especially relating to zooming.
Simply, there really isn't any control you have beyond that from System Preferences > Mouse where you can change the tracking speed, the direction of scrolling, single vs double button action, and turning zoom on and off. Changing sensitivity to touch just isn't there. The only solution seems to be getting used to the mouse and its behavior, though that is hard to say to someone who has used it for a year or more.
There isn't much to offer on controlling the magic mouse and its sensitivity.
Thanks, Ralph. Not happy with the answer but glad someone did answer. <g> I've been trying to sort out what it is I do that sometimes triggors the change but can't find it. It's more common at night so fatigue is probably a factor. It can change when I don't have my hand on the mouse but move over it on my way to the keyboard. Then there are times when a intentional swipe won't change it until the 3d or 4th try. Any idea what the mechanism of the action is? Could something on my fingers change the sensitivity? humidity of surrounding air? Proximity of the mouse to a sonic screwdriver?
There have been recent posts, as I said, concerning the zoom-double tap function and its sensitivity...with these mice Apple no doubt had to aim for a particular level for the general population. That is, steadiness of hand, eye-hand coordination, skin condition (not too moist not too dry), reflexes, and so on. So they end up using technology closely related to that of the iPad, iPhone, iPod touch screen, the track pad, and then hope the user fits the profile. Then add to that manufacturing tolerances just to make it a little more confusing. And you, the end user, have all of those factors to contend with.
And then they only give very limited controls for the mouse...but that may also reflect the technology and limits on what CAN be controlled.
Some controls you can alter; zoom you can turn off and use key strokes (command+ to zoom in, command- to zoom out), primary button for left/right handed users, track speed, single/double button function. So the user is left to decide just what to do in using the mouse.
Just some thoughts, Geoff. Not really solutions.