Meh. I bred beardies for quite a few years. In my experience they aren't the bonding type.
That said there are some lizards that show pretty decent intelligence for a reptile. Mostly monitors and tegus. And while they aren't lizards the crocodile family has some brainiacs (relatively speaking).
It tends to be the larger predators in the lizard family that have the smarts. I've seen nature documentaries where large monitors manipulate their environment such as turning over logs and knocking birds nests over in order to feed themselves.
I imagine irs because mammals and birds are the new commers on the evolutionary block. By the time they hit the ground there where already successful reptilian and amphibian species. The reptiles dominated for a while as the top predators and even the reptilian herbivores dominated the natural resources. It's very possible that early mammals evolved greater intelligence as a way to compete with them.