At what age can infants usually start to express laughter?

Infants typically begin to express laughter around the age of 4 months. At this stage of development, babies show an increase in social interaction and emotional expression. Laughter is a significant social milestone, indicating the child's growing ability to engage with caregivers and respond to stimuli in a joyful manner.

By 4 months, infants also have developed the visual and emotional engagement skills that allow them to react to funny faces, tickling, and playful interactions. This ability to laugh signals not only cognitive development but also the beginning of social bonding through shared enjoyment and emotional responses with others.

Younger infants, such as those at 2 or 3 months, may display smiles and other signs of happiness, but these do not typically indicate laughter. Similarly, laughter is more advanced than mere smiles and requires more sophisticated emotional and social development, which is adequately achieved around the four-month mark.