Have you heard the urban legend about a father finding out that his daughter was pregnant before his daughter knew she was? Or that story about how a friend was talking about something and next minute they had an ad for it on Facebook? Creepy? Or are we just that predictable?

Is Facebook listening to me? In short, no. At least not via the microphone on your device. But in a way, they kind of are. But in another way.

We’ve all had that moment where we were talking about something. And then you get an ad on Facebook or on the web for that thing you were just talking about. Most recently for me, it was talking about duck. Not the live bird, the cooked one. Specifically, Peking Duck. One of the tastiest things I’ve ever eaten. The topic came up in a Chinese Restaurant I was eating at with friends that didn’t serve this dish.

After we’d all departed, I came home and was laying in bed with a very full belly looking at my phone, and lo-and-behold, an ad came up for an album by a band called “Peking Duk.”

To anyone else this would be freaky and be crossing that “creepy line.” But I work in this field and know better. So a few quick messages around the friends who were at that dinner and I had solved the great mystery. No, Facebook wasn’t listening to our conversation. But Facebook did know a fair bit about what was going on in that restaurant.

Five people who knew each other on Facebook, Instagram and Messenger were in the same restaurant at the same time. Algorithms, GPS and the mobile networks had triangulated us all as being there. So, if all five of us are all connected each other, there was a good chance that we were all in that restaurant together. Probably in conversation with each other.

After a quick question to my friends, I found out that two of them had no idea what Peking Duck was. Three of my friends follow the band Peking Duk. The two who didn’t know what Peking Duck both at the same time did a search on Google. One did a search on Facebook for Peking Duck and got Peking Duk the band.

It’s not out of the range of reasonable to suggest that Facebook and Google could take a guess that everyone at that table was participating in a conversation about Peking Duck the food, or Peking Duk the band. And of course, we all got ads for the band and the food over the next 24 hours.

For end-users that might feel a little creepy. Which is why Facebook has added a link on each ad that allows you find out why you are seeing that ad. And while it doesn’t go in to every little data point that is gathered about you, you can rest assured that there are very real reasons why Facebook knows to show you that ad.