Thumb-sucking

We’re all born with a strong sucking instinct – without it we’d starve. Some infants suck their thumbs even before they are born, and some will do it right after being born– but from birth onwards we gradually unlearn that skill, from being weaned off the breast and given bottles, then cups, to drink from. It’s part of our natural progression from baby to adult.

Thumb-sucking can be a very helpful way for babies to cope with tension. There are many advantages to allowing children to suck their thumbs rather than a dummy: Thumbs are always there, don't fall on the floor, aren't tied to children's clothing by potentially dangerous strings that can get caught on things, and are under the baby's own control.
Children usually give up thumb-sucking when they develop other ways to calm down and comfort themselves, usually by ages 4-5, although many children suck their thumbs at night or occasionally, when stresses become too much, for many years beyond that.

Advantages of Dummy use

Undoubtedly, pacifiers can soothe a baby or to help them settle to sleep. Sucking on a pacifier can relieve pain, which is why parents often give their baby a dummy when they have colic or cannot be comforted. Studies have shown that premature babies transfer more quickly from tube to bottle-feeding, and feed more effectively from the bottle, if they are given a pacifier to suck on before feeds. Using a pacifier can also result in shorter hospital stays for preterm infants.