What about dropping a weight on a string from the attic and seeing if you hit something about 8 feet down? Of course there's always the possibility of X-bracing or other blocking in the way to make things confusing, but if you try a few stud bays you might get a clear idea. If you can drop 15 feet of string down in a few places you'll be pretty sure.
IR might help, but it might not. From the exterior, some buildings have a "warm rim joist" look when the walls are well insulated but the rim is not, and it's heated inside and cold out. If there's no insulation anywhere it's going to be hard to tell.
If it is true balloon you can tell from either the attic or the basement as David said. Also if the house is a 2 story the windows on the on the first and second floor will line up with each other. There are several different forms of ballon framing. I ahve seen balloon framing just between the windows. Or you can have balloon style framing from the attic to the second floor.True ballon is open from the attic to the basenent including the ban joist between the floors, which is another discussion