are you the first child in your family? Second? Third? Are you the only child ( no brother or sister )? This birth order is part of your environment. A new study from Stanford University California shows us something interesting. Birth order has influence on personality. the oldest ( first ) child is usually a careful, hard worker and often a leader. the middle child is usually friendly and loves to be with other people. the youngest ( last ) child likes to create new things. a child without brothers or sisters likes to be with adults, not just children.