He’s probably just giving you a slightly smart answer he thinks he can get away with. When he says that, try to give him a good-natured reply – something like, “Oh, of course you do. We all have imaginations, but we don’t always use them.” Or, “Sometimes our imaginations stay asleep more than we like.” Then give him an example of a time when he used his imagination. It wouldn’t hurt to think up one and save it until you need it in such a conversation!
It is possible that your son doesn’t know what the word “imagination” means, as it is a difficult concept to define for a child. You might try working it into something you praise him for. For example, if he draws a “silly” picture (funny hat, strange facial expression, etc.), you might say, “Boy, you really used your imagination in that!”
As for developing his creativity, exposure is important at his age. You have fabulous art museums in Houston, and most of them have exciting programs for children. See if you can’t enroll him in one of those. Tell him stories about your early life, and encourage him to make up stories about places you go or things you do together. And don’t push too hard on it. Remember that you want to help develop what is in him, not put something in that isn’t there or that wouldn’t find a good place to grow.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.