Thumb sucking is a common habit in young children that is considered normal up to ages 3-4. Persistent thumb sucking beyond this age can lead to malocclusions. Various theories have attempted to explain the root causes, including Freudian oral fixation theory and the rooting reflex seen in infants. Effects of prolonged thumb sucking can include changes to the dental arch. Management involves psychological approaches like parental attention and affection, keeping hands busy, and devices may help for difficult cases.