I know they don't understand, but I'm 100% certain that the geckos recognize my voice. I tell them all sorts of things, really, from asking the leo if she wants some crickets to telling the crestie that she needs to be cute cause my GF is having a bad day, etc. They also occasionally get scolded for worrying us. I don't think you're insane, as long as you're not expecting them to talk back.