For what it's worth, I don't think there's any hard evidence that big companies are doing this. Aside from the technical difficulties of constantly listening to

For what it's worth, I don't think there's any hard evidence that big companies are doing this. Aside from the technical difficulties of constantly listening to 1+ B mobile devices and running speech-to-text, it'd also be a legal quagmire. What's more likely happening is far more boring: humans as a whole are very predictable, and the metadata that Facebook et al have access to is more than enough to identify these patterns. To _really_ try and test this, you could download the Facebook (or Amazon or whatever) app, and (within earshot of your phone) consistently talk about some completely random purchaseable item that you have no intent to purchase and have never otherwise indicated you have an interest in. Chances are you will not get ads for it. To make it less likely you pick something that is subconsciously on your mind (and thus able to be picked up via your metadata), try playing word association games to pick the product in question. E.g. banana > yellow > raincoat > weather > digital thermometer