Compose a new message in gmail and it's hard to click on the Send button by mistake: It's the only button in red. (Wonder why the programmers didn't set up this "extra" color-coded signal for the "Reply" function as well . . .)
In a similar manner, I appreciate the "extra" raised dots on the "f" and "j" on my keyboard, helping me touch-type truly by touch, no peeking needed. They signal when my fingers are on the right keys, indicating that certain key strokes will be reinforced by enabling me to type what I need to (such as this blog post). I've often wished there were more such extra signals on the standard keyboard. In fact, to help me move the arrow keys efficiently, I put sticky paper on one--and that lets me navigate to the adjacent ones easily just by touch. My focus can stay on the monitor, rather than switching back and forth to the keyboard. I get things done faster.
Such redundancy in signaling has lots of practical applications. A couple years ago, I happened to get into conversation with a motorcyclist who commented on his efforts not to disturb the neighbors when he rode in late at night. I'd wondered why more work hadn't been done to muffle the roar of the engine. Turns out that motorcyclists--naturally enough--want to make a big commotion when they're on the roads risking their lives among the heavy bruisers like trucks and SUVs. Even subcompacts, for that matter. Like ambulances, they want to be both seen and heard so that other drivers can give them a safe berth. (Of course, the attention all the noise brings them can sometimes be rewarding in itself.)
That makes sense, but wouldn't it be great if motorcyclists could turn off the roar when they don't need it, like ambulance drivers do?