I'm in an old home and learned extensively about lath-and-plaster. I'm dealing with a problem like in What methods for installing light fixture in middle of room, with lathe and plaster ceiling?.
However, I don't actually know if my ceiling has laths or not. It's a beautiful coved design from the 1920s. I don't want to start cutting holes in my ceiling if there's any risk to damaging the keys given the age of the structure.
I doubt anyone can say better than 'probably'.
Mine do, except the ones that have been re-done over the years - roof/rain fail :\ - which are now plasterboard & skim. Good old moulded coving isn't a good clue, I made sure mine was kept intact whilst removing all the old L&P inside of that.
As a very rough guide… get some horizontal light on it & see if you can see hints of board edges.
Alternatively, if the entire ceiling could be considered 'wavy' or 'drooping' you've got semi-detached lathe & plaster.
If you cannot make that determination by eye, then just push a hole in it with a screwdriver & examine the layering in the hole. If there's paper, you have plasterboard, if you hit a lathe…
You're going to have to knock out at least an inch circle to work through anyway, so you'll quickly find out.
Also consider that if there's floor-boarding above it, then you're going to have to take some up anyway to get the cabling in - at which point you'll be dead certain. If it's a part of the ceiling that's never previously been penetrated, you'll also have to come in from above to put noggin[s] across to be able to precisely place the new fitting securely. You can't fasten into 100-year-old L&P, & I have a mistrust of plasterboard's strength anyway, so I'd fasten to wood even then.
If you absolutely cannot get above it - if you're in a shared property of any sort - then you're going to have to cut sections out of the ceiling itself to get cabling across & noggins in, then re-finish.
