Question
The book says that a 4-month-old baby’s actions should show symmetry. What does that mean? Does it mean that at all times, both arms of the baby must move in the same way, and both legs must also move in the same way? But my baby isn’t like that.
Answer
Hello, your child is perfectly normal and there is no need to worry. The principle of action symmetry refers to the economic rule of achieving the greatest work effect with the least amount of effort during operation. In factories, we can see many actions that do not conform to this rule, which can reduce work efficiency and make people more prone to fatigue. If both hands only perform actions in one direction, it can cause the body’s center of gravity to shift and requires a greater mental and muscular effort. Bilateral symmetrical actions with hands are the most energy-saving way of working. Therefore, your child’s current way of moving is very normal.