For the last couple of months Daddy has been picking Saylor up and showing him how light switches work and Saylor was enjoying the "game" Then Saylor's Nana and Opa came from Calgary to visit for two weeks and Opa contined the light switch "game" and Saylor learned to say "on"! It is very cute Saylor points to light and says "on". The light could be the overhead light in the truck, or a light at a friend's house. He definitely understands the concept of turning the light on and off. The only challenge is that Saylor wants to turn the light off and on all day long.