There are several possibilities but these are the most frequent ones: 1) Abnormal mouth resting posture, especially when the tongue is down and forward. Sometimes there’s mouth breathing, sometimes, not. A plugged nose causes the jaw to lower, lips to open, and the tongue to rest down, or down and forward. 2) Digit (thumb or finger) sucking and excessive pacifier use keeps your tongue pinned to the floor of your mouth and encourages your tongue move forward and back. It gets used to that movement pattern and your swallow follows suit. 3) An openbite (vertically parted front teeth) encourages the tongue to move forward and swallow there. The openbite may, or may not, be caused from digit sucking. 4) Large tonsils can encourage your tongue to move forward and function there.