It is normal for three-month-old babies not to be able to laugh out loud. According to the process of pediatric mental development, infants usually do not laugh out loud until they are about four months old. At 3 months, infants can show that they can change from supine position to lateral position by themselves, can touch things with their hands, learn to babble and pronounce words, can turn their head 180° with the objects they see or hear, and can notice their own hands. Four-month-old babies can laugh out loud and can show joy when they see food. Therefore, it is normal for three-month-old babies not to be able to laugh out loud and there is no need to worry too much, so you can always observe the dynamics of the baby. If the baby has developmental abnormalities and still can’t laugh out loud even after the month is over, it is necessary to consult a doctor in time.