Does being a firstborn, middle child, last-born or only child have an effect on your personality, behavior, or even your intelligence? While the possibility has been challenged, our birth order is believed by many to have an enduring impact on our psychological development and adult relationships.

Firstborns are often described as being high achievers who seek approval. They’re also described as cautious, controlling, and reliable. Firstborns and only children are the only siblings who are allowed to bask in their parents’ undivided attention (for better or worse) with no distractions from siblings. Studies have confirmed that without question, firstborn children are offered more individual and uninterrupted hours of their parents’ attention, which may, in fact, allow for relatively greater gains in intelligence.

Middle children are often described as being peacemakers. They are often people-pleasers and tend to have a wide circle of friends. Concerned with fairness, middle children are typically viewed as possessing a wide set of navigating and negotiating skills that serve them well in their intimate social circles and employment.

Youngest children are often described as fun-loving, outgoing, carefree, and self-centered. While youngest children may feel less capable in comparison to their more experienced older siblings, they tend to be more pampered by their parents and maybe even their older siblings. The stronger social skill that often can result can contribute to an image as charming and well-liked.

Only children are often described as mature for their age, in part as they are likely to be primarily surrounded by adults. Only children are often referred to as perfectionistic, conscientious, diligent, and leaders. Only children are seen as rule-followers who tend to be resourceful, creative, and independent.

Such descriptions likely sound familiar to you, and they should, because they make up much of the stereotyped mythology about birth order. But studying birth order is no easy task, and ongoing research has yielded mixed results and has been widely criticized throughout the years. For example, is it simply parents’ interactions with their children that impacts how birth order shapes personalities and predicts behaviors? Of course not. What about the sex of older or younger siblings? For example, while Sue may be the second born child, if she has an older brother, she can also be seen as the firstborn female within the family, which would also undoubtedly shape her personality.

How about the effect of children’s innate temperament, independent of their birth order? The effects of being adopted, or blended families? And, what about the often subtle and unconscious impact of perceptions and stereotypes about birth order on parents’ reactions to their children and on the children themselves? The list is endless, and as we begin to factor in individual differences including ones’ own (positive and negative) life experiences, we see how complicated attempting to study birth order becomes.

So, while we may be quick to judge people by their birth order, our personality, behaviors, and intelligence are impacted by many variables, only one of which is our birth order. Despite the mixed and often controversial research on birth order, understanding your role within your own family system may help you also understand the connection between your family position and behavior.