Is it normal to be able to suck in your ribs as well as your gut?

So I've got a few interesting things I can do with my body that I've known about since I was a kid, for example bending my thumb backwards, but the one I've never really been able to understand is that I can suck in my ribs. Most of my flexibility quirks I can just attribute to being double-jointed, but the ribcage doesn't exactly have any joints.

I guess the best way to help you all visualize what happens is to describe how I do it. It's not exactly like sucking in my gut in reverse, but rather more like trying to breathe in without opening my lungs or something so they just contract inwards and my chest visibly bends backwards in the middle. I've tried Google searching numerous combinations of keywords related to this, but no matter how I phrase it the results always come up either being about sucking in your belly or people removing ribs to enable self-sucking.

So basic yes or no type is it normal question, anyone ever noticed or heard of this being possible before?

Also on a side note my very bottom (floating) ribs seem to stick out more than the attached ones and I can actually push the skin under them and feel inside my ribcage with my hand a bit. Dunno if that's a factor or not, but it could be somewhat relevant.