As anyone who has ever raised a child will know, parenting (in whatever form) is a scale-up problem. Each child is the product of many complex and interacting variables. Some of the obvious ones include: likes and dislikes; temperament; learning preferences; and emotional, social and physical needs. None of these are constant, and all of them change as the child grows. Most people deal with this challenge with the help of more experienced parents and caregivers, by reading books on parenting, or, most often of all, good old trial and error.