The Google Home product also listens to the "OK Google" command.
So how can the uncanny AutoComplete options reported by some users be explained?
I think the best explanation is that Google is producing AutoComplete options by means beyond the user's understanding. Consider four possibilities.
Let's say you do 100 searches using Google Search. Probability would suggest that AutoComplete will be helpful some of the time, useless some of the time and uncannily accurate some of the time. Sometimes a specific thing you're searching for just happens by coincidence to be something lots of other people are searching for, and therefore shows up in AutoComplete. Sometimes you believe you're coming up with a search query out of the blue, but in fact you've been influenced by social trends online.
Google claims it doesn't listen to "utterances" -- chatter unrelated to a specific voice search or command. But sometimes it does. On my own "My Activity" page, more than 10 percent of the recordings don't fit Google's criteria for audio that should be recorded and retained. In one case, someone I know who speaks with thickly accented English says something that sounds exactly like "OK Google," but that's not what she said. In others, I don't hear anything remotely similar to "OK Google" on the recording. I just hear a snippet of conversation. Still, a short one- or two-second sentence of otherwise random conversation was recorded in each instance, and the words therein could have been factored into a set of AutoComplete options.
In other cases, it's possible that words spoken in the background or immediately after a legitimate "OK Google" command could be included.
Here's another scenario. Let's say one person has enabled the "Trusted Voice" setting on a Pixel phone. This person is visiting a friend, who's got a Google Home device. The friend says to the Home device: "OK Google, how tall is Taylor Swift?" Two days later, after forgetting the result, the friend with the Pixel goes to do a search, types in "how tall is" and AutoComplete offers "Taylor Swift" in the options. Was Google listening? Yes: The other person's "OK Google" command also triggered and recorded on the Pixel phone without the knowledge of the user.
3. Unexpected sources for signals
It's clear that with Google Maps, Google includes AutoComplete options based on not only my activity, but my wife's. It's easy, based on activity, for Google to figure out who's intimately connected. For example, it should be clear to Google that my wife and I, who are both heavy Google Maps users, usually travel together to the same GPS coordinates and addresses.
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