The inscrutable purpose of Mac controls

I just got a new Mac for the first time in ages. I was a complete Mac fanatic at the dawn of the Macintosh age, but eventually moved over to Windows since that’s where the action was. I’ve taken a look at OS/X numerous times, but playing around with a product for a short while isn’t the same thing as sitting down and really trying to use it to get something done.

I’m constantly struck by how little effort OS/X Tiger expends in bothering to explain the purpose of controls. Most of the bundled apps include their own collection of beautifully rendered little widgets whose purpose is often difficult to discern. My favorite example is the little glass bead found in the upper right corner of numerous windows for expanding and collapsing the toolbar and sidebar:

The glass bead in the upper right corner surely represents some sort of high water mark for obscurity. No text or icon to detract from the purity of the lovingly rendered glass! Maybe hovering the mouse over it produces a little tip window? Nope. (Why the heck not?) The search box, at least, uses a magnifying glass icon to suggest its purpose, even if the icon is highly abstract in both visual representation and concept. It’s hard to think of a control that communicates less about its purpose than this little glass bead. (But not impossible – perhaps we should be grateful the bead is at least adjacent to the region of the window it affects.)

The new user looks at the control and wonders, "What the hell do you do?"
The control gives its stony reply: "If you must ask, you are unworthy."