Um...No Thank You

Luke says, "no thank you" to most things these days. Me, "Do you need to go sit on the potty?". Luke, "um...no thank you". I get the same response when I ask him to come to the table for dinner, take a bath, go to bed, etc. At least he is polite, right? I do have to turn my head and giggle sometimes when I hear him respond this way. He is politely being defiant at times.