1. Physiological characteristics of four-month-old babies Four-month-old babies have begun to have their own biological clock and can distinguish between day and night. Their heads and torsos are relatively stable, allowing them to hold their heads up and even sit up. Begins to develop coordination with hands and feet and is able to grasp objects and place them. In addition, the vision and hearing of a four-month-old baby are also developing. Feeding methods for babies in two and four months. At this stage, breast milk or formula milk is the baby\’s only source of food. It needs to be fed 5-6 times a day, and the amount of each feeding is about 120-180 ml. If your baby has picky eaters or indigestion, you should seek medical attention promptly. three,