Mature swallow pattern is characterized by all of the following, except:
Humans show 2 types of swallow patterns:

Infantile and neonates swallow
Mature/adult swallow.

Infantile swallow  is characterized by:

Active contractions of the lip muscles.
Tongue is placed between the gum pads and tongue tip is brought forward into contact with the lower lip.
Little posterior tongue activity /pharyngeal muscle activity.
Tongue-to-lower lip posture adopted by infants at rest.
Contraction of lips and facial muscles helps to stabilize the mandible.
Vigorous mandibular thrust.

Physiologic transition of swallow begins during the 1st year of life and continues for several years. Mature swallow is seen usually by 4-5 years. Maturation of swallow pattern occurs with the addition of semisolid and solid food to the diet. Increasing activation of the elevator muscles of mandible is seen. When sucking activity stops, a continued transition of swallow leads to acquisition of adult pattern of swallow.
This swallow is characterized by:

Cessation of lip activity, i.e, lips relaxed.
Placement of tongue tip against the palate and behind upper incisors.
Posterior teeth into occlusion during swallow.
Downward and forward mandibular growth increases intraoral volume and vertical growth of the alveolar process changes tongue posture.
Mandible stabilized by contraction of muscles of mastication.

Ref: Textbook of orthodontics 2nd ed Gurkeerat Singh page no 595,596
Relaxation of lips
Placement of tongue behind the maxillary incisors
Placement of the mandible until posterior teeth are in contact
Relaxation of the elevator muscles of mandible