Probably using any sort of electronic device. I have seen parents handing their toddlers phones and tablets just to keep them occupied. My daughter is 6 and we still struggle to figure out how much screen time she can have because while we want her comfortable with the digitized world there is a noticeable change in her mood and behavior if she spends too much time on the tablet. She does her lessons on a laptop and that doesn't seem to have the same effect but it is also something to consider when allocating her tablet time. Try to get her outside for a walk or play every day and give her lots of time to play with her toys or draw/colour etc so she gets varied activity not just a full day of screens.