I believe the answer is: Is fixated, or stuck in the oral stage of development
During the oral stage of the develoment, we had the inherent belief that our mouth is our primary active organ. This make us have the tendency to put different types of objects into our mouth (usually happen when we are 0-2 years old) . Failing to pass this stage of development would resulted in us constantly develop the needs to put foreign objects such as gums or pencil in our mouth.