 That's kind of weird to have that many pens with no paper. That's not going to work, yeah? So that's not what it's about. It's here for an example. Okay, ready? This is stimulus preference assessment. So, in short, what we're going to do is go, what do you want? That one. All right. I'm going to write that down. He goes, yellow pen, and I'm going to go, what do you want? Sunglasses. Sunglasses. Okay. He wants the sunglasses. You write that down. And then you're going to go, what do you want? Pen. Cool. You wanted the pen. And then we might go, what do you want? Side preference, side preference. Ah, it's proven me wrong. Change it for a reason. You'll find out later in a lecture. And he knew about it anyway. So the idea is, we're going to go through and go, A, he picked this last, and B, because these are similar stimuli, he most likely likes pens over sunglasses. But we would continue in that fashion of removing items and tracking which ones in order to see which ones are most preferred, which are not technically reinforcing. Go see that video.