It is normal for two-month-old babies to enjoy sucking their fingers, as it provides comfort due to their sensitive oral cavity.

When babies around 40 days old start to exhibit behaviors like hitting their heads and rubbing their faces, possible causes and solutions.

Sucking on fingers is a normal behavior for a four-month-old baby, indicating their hand-eye coordination and finger function are developing. However, if this continues without other development, it may become a bad habit.