In more recent years, the original Piagetian object permanence account has been challenged by a series of infant studies suggesting that much younger infants do have a clear sense that objects exist even when out of sight. Bower showed object permanence in 3-month-olds. This goes against Piaget's coordination of secondary circular reactions stage because infants are not supposed to understand that a completely hidden object still exists until they are eight to twelve months old. The two studies below demonstrate this idea.