It is no coincidence that most Santa-believing children lose their faith in the jolly bearded fellow at around age 8 or 9, finds a recent study that explains why this period marks an important shift in human development.

Kids at this time usually improve their conceptual abilities, developing a better understanding of underlying causes behind physical realities and the information that they receive. The period also marks the birth of skepticism, helping to explain why so many of us feel a loss of innocence and unquestioning joy at this time. Often the word “magic” is later used to describe the lost phase.

Santa is all about magic, requiring incredible faith even to entertain the idea of his existence.

“Santa is purported to engage in activities that violate physical principles known even to infants, at least on an implicit level,” wrote researchers Andrew Shtulman and Rachel InKyung Yoo in the study, published in the journal Cognitive Development. They are both in Occidental College’s Department of Psychology.

“For instance,” they added, “Santa violates our expectations about spatiotemporal continuity by visiting all the world’s children in a single night; he violates expectations about containment by entering children’s houses through their narrow chimneys; and he violates expectations about support by flying through the air on a wooden sleigh.”