ds (3yo) is suddenly being really rough with dd (11 months) and pushing over - including pushing her down the stairs this evening. we've never used the naughty step before, and tried today but to be honest our hearts probably weren't in it, and he just kept getting off and wanted to talk to us. It doesn't sit very easily with me to put him somewhere on his own as a punishment, when he doesn't seem to understand it as a punishment anyway, and really I want to get to the bottom of what is going on for him, and help him to find better ways to treat dd and/or deal with his anger/frustration if that is the problem. Any suggestions for an alternative approach for dealing with this while being very clear that he must not do this? I've so enjoyed being able to leave them to play together and can't see how I will get anything done in future if I have to keep dd always within sight.