At this age they try out different kinds of behaviour to see what effect they have - particularly on other people. And how much control they can get on other people. If the consequence is a bit of drama, someone else yelling, lots of attention etc then this is a reward for the behaviour and will encourage the behaviour. If the consequence is something like getting put straight in the buggy, strapped in, taken home then it will not reward the behaviour. Or tuck her under his arm and march off, without paying her any attention... If she screams ignore it. Whatever happens don't reward it. It's not a case of punishment - rather a case of not rewarding in any way.
It's hard isn't it because some children just don't happen to try out this stuff and others really go for it.
Another stabbing in Sydney today.
Do you still wear you original wedding and engagement ring