The attention span of a young child is minimal at best! If you can get a three year to attend to a cartoon for ten minutes then you are doing well! Learning to sit and attend for long periods of time is considered developmental in nature. So, expectations should be age appropriate and ten minutes is about the right amount of time a child of three will sit as they also are being drawn to exploring their environment and don't put a high value on TV, as say an adult would. Note: Some children may attend a little bit less, while others more.