The infant’s mouth and tongue comprise a highly specialized system used to ingest
nutrients, express emotions and promote self-comfort, such as sucking on a breast,
pacifier, finger or thumb. A MEDLINE® search covering the last 35 years revealed
more than 1200 studies published on these topics in relation to infant sucking.
However, few studies were found regarding the mouthing of objects by infants for
the purposes of exploring, perceiving or learning about properties of objects (eg,
texture, hardness, temperature).