If you have installed google toolbar, google may identify you. Google can identify you by IP, cookies, geotargeting (if all clicks are from same city) etc...
by gps. there is a gps installed on every motherboard so every clicks, google will check the location of click im just kidding
Google is standing behind you as you read this But yeah all of the mentioned ways, they have plenty of ways to track us.
They just know, it's like when you were a kid and your mum always knew that you had raided the cookie jar. It's the guilty look of your site statistics.