My 3-year-old is a good boy. However the last few days he has been so defiant and aggressive. Yelling, hitting, throwing toys, kicking things, having temper tantrums and just about anything else you can imagine if he doesn't get his way. Nothing has changed in our home environment and we have tried reasoning with him, time-outs, holding him to calm him down and everything. Is this normal behavior?
It is not unusual for children of 2 or 3 to have angry "tantrums"--reactions of yelling, throwing things, hitting, and general loss of control. It is good to search for something in the child's life that may have changed--as you yourself has suggested--since often tantrums are a response to new elements that throw the youngster for a loop: a new sibling, change in caregivers, or emotional events at home. But oftentimes there is nothing particular that parents can identify that has set the tantrums into motion. The "change" may be that the child himself is maturing, and has new ideas a new worries; the child suddenly understands more about the way the world actually works, and feels suddenly less in control and less secure because of this. It is part of growing.
I would suggest therefore, that you attempt to do whatever you can (realistically!) to avoid setting up situations that seem to provoke tantrums, and then to try to calm your son and get the day back on track. Recognizing that tantrums are not unusual and that the best thing to do is to maintain your cool--these ideas may help. Punishment, time-out, and other efforts to intervene directly with the tantrum "behavior" usually do not, in my opinion, get anywhere.