How old is your son? At an early age this is a common problem. Dear,; don't force him to be what he is at home, outside too. Simply make him understand that unless he talks more and makes new friends outside, he will feel lonely as he grows up.; Don't pressurize him assure him how smart he is and how he can actually gain more friends if he is a just a little more talkative outside. Give some time. Things will sort out.; Also, keep communicating openly and never let him sulk around. Ask him what might be bothering him too