I did that experiment this morning -- before work at home and on the way to work, my wife and I were discussing getting a new car, and spoke about a particular car brand that a coworker just purchased.

I just asked her to check her Facebook and she doesn't see any car ads. I checked too but didn't see any ads for cars or that brand, but I don't have the Facebook app on my phone (she does) and our Facebook profiles aren't strongly linked (i.e. she's not listed as my "wife", we just friend each other). She uses her phone for navigation while driving, so it was in a position to clearly hear us.

I haven't done any research on that car brand, but I suspect that once I do a Google search, then the ads will start flooding in.

So maybe this is confirmation bias in the other direction, but I don't see any evidence that Amazon Alexa, Facebook, or Google Assistant are spying on us. Though it could just mean that this particular carmaker doesn't purchase ads based on keyword spying

For experiments like this, use items that have high CPM. Gold, silver, niche personals and preserved food are great canaries.

Try doing different things. I don’t think name brand vendors do pervasive audio surveillance. I do think they broaden the scope of your intents. Use GBoard dictation or similar tools to write. Write stuff down in different contexts. Use apps in different ways.

Amazon and Facebook share in near real time. Anything you do in a consumer Amazon property is feeding context to FB.

Sorry, I didn't mean to imply that I wanted to do this test, I just happened to do it by accident this morning -- using a very similar term as the writer of the parent post, he said he mentioned Scion, I mentioned another major car brand that starts with S.

But you aren't being recorded or listened to. Countless security researchers have dug into this problem and can tell from the traffic that there is audio being recorded. Furthermore, if facebook is accessing the microphone without permissions, it would be through an unknown security vulnerability and would be against the terms of service with both android and ios.

You are just not noticing these ads until it is something you have called out. You would never have given a second thought to this totally random item otherwise.

I have tried the same test as you multiple times just for kicks and have never found it to be confirmed.