Motor Learning Term of the Day

Inhibition of Return (IOR): the delay in responding to the previously cued (or orienting) stimulus/stimuli.  

In the field of infant feeding, infants are often observed to inhibit the reflexive lunge toward the breast following a learning experience with an artificial nipple, regardless of whether the artificial nipple is a pacifier (soother or dummy) or a bottle nipple. 

In many infants, this inhibition is displayed as slower speed and less accuracy as the infant moves toward the nipple-areolar complex for the oral grasp/latch, and this can be studied and measured in milliseconds as a prolonged movement time [MT] for the oral grasp.  Other infants can achieve and sustain the oral grasp at the breast after a learning experience with an artificial nipple, but display an inhibition of the reflexive wide oral gape in order to learn the shallow oral grasp of an artificial nipple, and the shallow latch is a well-known risk factor for maternal nipple pain and nipple trauma.  In yet other infants who have been given a learning experience with an artificial nipple, there are observable displays of ineffective suckling which can result in inadequate transfer of milk.  An infant may display such learning difficulties (task-switching difficulties with subsequent switch costs of decreased speed and accuracy) in one of these areas, while other infants will display feeding difficulties in some or all of these areas. 

When infants are given a learning experience with an artificial nipple and are subsequently returned to the breast, some infants no longer move toward the nipple-areolar complex at all, as if waiting for other, more recently learned feeding stimuli to be offered.  

Lactation consultants are often consulted to assist the infant in returning to the breast when such difficulties occur, particularly in non-Baby Friendly childbearing facilities.  Clinicians often provide manual guidance to the mother in positioning the infant at the breast for the infant's correct trajectory toward the nipple-areolar complex, as well as manual guidance for the necessary speed in moving toward the nipple-areolar complex while the infant's mouth is reflexively open for the oral grasp, and also while the infant's tongue is reflexively extended over the lower alveolar ridge for the oral grasp.  Less tongue extension is needed for bottle-feeding skills, and during task-switching difficulties between breast and artificial nipple and back to the breast again, even the baby's reflexive tongue extension for the oral grasp can be inhibited for the oral grasp of the nipple-areolar complex.   

When a breastfeeding mother bottle-feeds her infant and subsequently returns her infant to the breast, the mother has often positioned her baby at the breast but in a bottle-feeding position, i.e., the baby is often cradled in one arm and reclining in a supine position.  With verbal and manual guidance from the clinician, the mother can quickly relearn how to position her infant at the breast, but the infant's primitive survival reflexes are often more heavily weighted toward the more recently learned feeding method, rather than equally weighted for all infant milk-feeding methods all the time.  Even the novice clinician is undertaking her own motor learning toward increasingly greater motor control.  The clinician often provides verbal and manual guidance to the mother in learning how to position her infant at the breast, and also in learning how to guide her infant in learning the oral grasp and/or effective suckling. 

Motor learning is complex, and this also applies to the mother who is also learning how to comfortably hold her infant in nursing positions, while also learning how to provide manual guidance to her infant in helping the little one to learn the oral grasp.  The mother's advantage is that she has spent a lifetime in learning her own feeding skills and other many other skills with the repetition of task-specific practice.  Nature provides remarkable assistance to the newborn mammal by endowing preadapted feeding movements that are further adapted in response to feeding stimuli.  However, these preadapted feeding movements, i.e., the primitive survival reflexes, are often more heavily weighted toward the more recently learning feeding method, an elegant and efficient approach by nature in support of the newborn's survival.  Particularly during early learning when early motor memories are most fragile, task-switching from breast to artificial nipple and back to breast is often challenging for the healthy term infant, and the challenges may be mild, moderate, or pronounced and prolonged.    

Without the presence of the infant's primitive survival reflexes, motor learning for milk-feeding skills would occur too slowly for the newborn's survival.  Consider the weeks of practice needed by the 6-month-old who is learning how to transfer liquid from a sippee-cup, and the difficulties displayed by the older baby when a different style of sippee-cup is offered.  The frequent response by many babies is a clear refusal of the novel sippee-cup, particularly during early learning.  Similarly, bottle-fed infants often display a preference for one style of artificial nipple, struggling with and often refusing a novel artificial nipple.  

When infants are exclusively bottle-fed, regardless of whether the milk is mother's milk, human donor milk, or artificial infant milk, it is also important to observe and study how infants learn to inhibit the reflexive lunge toward the bottle nipple.  In bottle-feeding, the reflexive lunge toward the bottle can be observed during earliest practice sessions in bottle-feeding, but as more practice sessions in bottle-feeding take place, newborns learn to inhibit this reflexive lunge toward the bottle very quickly, an example of the exuberant learning of infancy.   

This is a dramatic and profound display of infants learning very soon after birth to inhibit a reflexive movement when this reflexive movement is not at all needed for bottle-feeding.  The reflexive movement/lunge toward the breast is genetically designed for infant mammals to be a forward movement toward the nipple-areolar complex, but this reflexive lunge is highly adaptable in the manner of a heavier weighting toward the more recently learned milk-feeding method.  Bottles are consistently moved by the parent or other caregiver toward the baby for feeding, rather than the inefficient movement by the parent of moving the baby toward the bottle.  As the parent or other caregiver quickly learns to be efficient in their bottle-feeding movements, newborns also become quickly efficient in inhibiting the reflexive lunge that is needed for the oral grasp at the breast, but not at all needed for bottle-feeding. 

Learning is most rapid in infancy, but the cognitive demands of task-switching are greatest during infancy.  Across the lifespan, cognitive flexibility is most limited in the young.