Just in one ear and out the other. That's what parents of toddlers have thought for generations. But now there's new research that toddlers do listen and will obey, but maybe just not right away.
Here's an example from psychologists at the University of Colorado at Boulder: Say you tell your child to go and get a coat because it's cold outside. A three year old can't process that. The child is too young to understand why he or she needs to put on a coat indoors, for something that's going to happen in the future outdoors. In toddler-logic, the child needs to experience the cold first, and then will remember the parent's advice to go and get a coat.
The researchers suggest a different approach. Say: "I know you don't want to take your coat now, but when you're standing in the yard shivering later, remember that you can get your coat from your bedroom."
The study is in the Proceedings of the National Academy of Sciences.