Logic Pro X - Why do the selected tracks enlarge automatically?

Okay. So this isn't really a "problem" per say (if that's how you spell that, lol), but it gets annoying and what's even more annoying is that I can't seem to figure out what triggers it.

But sometimes when I'm working in Logic, the tracks will begin to automatically enlarge as I select them. The unselected tracks go back down as I switch, as if I'd accidentally hit a shortcut button that I didn't know about or something.

I've included a screenshot so you can see just what it is I'm talking about, hopefully. There must be some way to toggle in and out of that mode that I just can't see, I'm thinking.

Thanks,

Matt