More Than Reflexes

by Debra Swank

"Motor skills do not just come as birthday presents. They must be nurtured, promoted, and practiced."

- Kinesiologist Jane E. Clark (2007)

    The six-month-old baby latches quickly and feeds contentedly, pausing now and then to grin at his mother while sustaining the latch. He can simultaneously nurse and explore his immediate world, reach for his toes, then play with a button on his mother’s shirt, all without losing the latch and without any interference in his ability to swallow big gulps of milk.  This is Advanced Breastfeeding, a brilliant display of automaticity(1) in which his feeding movements have become nearly automatic – more smooth and fluid, with less attention focused on the task.

     Reflecting on their own increase in skill, his parents recall the awkward difficulties in learning how to pick up and carry their newborn, how to diaper, bathe, dress, and embrace him.  Although automaticity is impossible for the novice, the repetition of practice helps to build motor memory, and now the parents have become so highly skilled that bathing, diapering, and dressing the baby is no longer a stressful ordeal.  While the baby feeds at the breast, now his mother can also coordinate a walk to the sink, then pours a glass of water to quench her own thirst.  How did this family learn to do so much? 

     We begin learning during our gestation, building auditory memory for familiar sounds and olfactory memory for familiar smells, and some of us even build early motor memory for sucking on one’s tongue, thumb, or fingers while in utero.  As newborn mammals, we enter the world in possession of the primitive survival reflexes, pre-adapted motor behaviors that support our earliest sensory-perceptual-motor learning (or more simply, motor learning) in the acquisition of motor memory for infant milk-feeding motor skills.

     The crawl reflex and the rooting/search reflex enable us to locate our food source, and once found, the oral grasp reflex supports our learning for attaching to (or latching onto) the maternal nipple-areolar complex.  As the mother’s nipple touches the baby’s palate, the suck reflex is stimulated, and when milk release soon occurs, our swallow reflex is stimulated, as we learn how to better coordinate sucking and swallowing with breathing.  Should we become disorganized during a swallow, our cough reflex supports us across the lifespan in becoming reorganized for drinking and feeding.  As babies rehearse their feeding movements, the sequenced coordination of these reflexes is a marvel of motor learning in the young, yet the presence of these primitive reflexes does not guarantee latch and effective suckling in all babies all the time.  Our primitive reflexes are better viewed as training wheels on the bicycle, hastening our motor learning toward motor control for milk-feeding in dramatic support of our survival.

     Lactation specialists often cite the “hard-wired” nature of the primitive survival reflexes, but clinicians also frequently observe the baby’s newly acquired feeding difficulties or skill decay(2) for latch and/or effective suckling that often follows the baby’s learning experience with an artificial nipple, and this skill decay is displayed as decreased speed and accuracy for the task.  In the 3rd edition of La Leche League International’s Breastfeeding Answer Book, authors Nancy Mohrbacher and Julie Stock note that supplements have been associated with breastfeeding problems ranging from breast refusal, incorrect sucking technique, and severe breastfeeding problems(3).  The authors advise, “Although most babies may be susceptible to breastfeeding problems caused by early bottle and pacifier use, it is generally agreed that once a baby has been breastfeeding well for three to four weeks, problems are less likely to develop, so if a mother plans to give her baby bottles or pacifiers, suggest she wait until after her baby’s first month or so to introduce them”.(4) Exclusively bottle-fed babies often display feeding difficulties when given a different style of artificial nipple, and some mixed-fed babies (who have learned how to breastfeed as well as bottle-feed) often display a preference for a particular style of artificial nipple while bottle-feeding, struggling with or refusing a new style of artificial nipple, followed by acceptance of a previously learned style of artificial nipple. The term motor memory consolidation(5) refers to the process by which an initially labile memory trace reaches a robust and relatively fixed state for motor control, a process that is heavily reliant upon the repetition of task-specific practice as well as sleep(6-10). 

     More months go by, and the baby becomes a toddler who is soon willing to practice eating with his first spoon and first fork, but more months of practice are needed to build rudimentary skill for these new feeding techniques. “Utensil confusion” (a close relative of “nipple confusion”) is often displayed by the toddler who, in mixed-up fashion, attempts to use the spoon in the manner of the fork. Frustration frequently arises during the early learning of this new skill, as evidenced by the toddler who pushes away the spoon and fork, then happily returns to his skilled manual grasp of the food. In observing their toddler’s difficulties during early skill acquisition for utensils, many parents opt to put one utensil aside for several weeks, affording their toddler the opportunity to build robust motor memory in learning to use one style of utensil.

      While continuing to observe his family at mealtime, the toddler is soon motivated to practice again with both utensils.  Motivation(11) is a factor in learning, and some of us are sufficiently motivated to further add to our motor skill repertoire by learning, with much practice, to eat with chopsticks — and Utensil Confusion Part 2 ensues. Even though the trajectory from plate to mouth is the same for eating with a fork, spoon, and chopsticks, learning the manual grasp of chopsticks after some mastery of the spoon and fork is cognitively demanding — so much so that many individuals will decline to ever attempt the awkwardness of learning to use chopsticks again.  This does not result in a feeding crisis or dilemma, since our remaining skills for eating and drinking are more than enough to support our survival.

     And so it goes.  The challenges in discerning the similarities and differences in people, objects, and experiences are not limited to the newborn, the older baby, or the toddler. We often experience a challenge in differentiating one very identical twin from the other, and years of sensory-perceptual learning are needed in order to be able to discern various types of red wine from another (for the sommelier, even more intensive learning is required).  Across the lifespan, sensory-perceptual-motor learning is easiest and most effective when practice is specific to the task, termed practice specificity(12).

The greater the difficulty of the task, the greater the need for practice that is specific to the task.

     Should a young child receive a traditional tricycle from his parents as well a big-wheeled tricycle from his grandparents, the child will rapidly display a preference by spending far more time learning to ride just one of these trikes. Having quickly learned that it’s too difficult to learn tricycle-riding by practicing with one tricycle today and another similar yet different tricycle tomorrow, most (if not all) early rehearsals are naturally and voluntarily spent on just one tricycle for the most rapid skill acquisition.

     When the professional musician is preparing for a critical audition using a clarinet, he will never choose to practice the clarinet on even days and the oboe on odd days, since there is a world of difference in the oral grasp for each of these similar but very different instruments.  Rather than surfing in the ocean, the elite snowboarder will rehearse for the Olympics by using a snowboard, and furthermore, the Olympian will use only her own snowboard for practice.  The elite baseball athlete will never prepare for the World Series by rehearsing with a softball instead of the baseball, and the professional classical singer will not prepare for a Mozart opera by rehearsing only Verdi or Wagner.  Should the athlete or musician rehearse by task switching(13-15) between similar yet different equipment, adaptation will surely take place, but such adaptation is considered costly in regard to the subsequent and observable performance decrements or switch costs(13-15) of reduced speed and less accuracy when returning to performance of the original task.

On Interference, Flow Confusions, and Flow Preferences

     For much of the day, our skills are casual and non-competitive.  On the way to work, we may drive a loaner car while our own vehicle is being repaired, but when we’re back behind the wheel of our own car, there’s a bit of happiness for the feel of it – our sensory-perceptual-motor memory for our own motor vehicle.  After arriving at the office and sitting down at the computer, we frequently experience interference in memory retrieval when our encoded memory for an old password interferes with our ability to recall the most recently created password. To build robust memory for the new password, the repetition of practice is necessary to form and strengthen new synaptic connections for that specific numerical sequence, along with sleep. 

     During proactive interference(16-17), old memories interfere with the retention of new learning, such as the common difficulty in remembering a new password.  During retroactive interference(18-19), new learning interferes with the retention of old memories.  When switching from your old car to a new car, have you ever reached incorrectly for the gear shift or radio knob in the new vehicle?  In this case, robust spatial memories (memories for the layout of the space in your old car) have interfered with your spatial and motor memories for the location of the gear shift or radio knob in the new car, but with a little more practice, you will be back in the groove of automaticity once again.

     In 1995, Neifert, Lawrence, and Seacat(20) provided an early formal definition for the phenomenon of “nipple confusion,” utilizing the learning term interference.  When a baby learns the requisite shallow latch with an artificial nipple, followed by a learning experience at the breast, many babies are subsequently unable to achieve the oral grasp (latch) in spite of observable attempts to do so, in an example of proactive interference.  When a newborn learns how to latch and suckle well for the first breastfeed after birth, then is subsequently given a sensory-perceptual-motor learning experience with a pacifier or a bottle-feeding, there are often new displays of difficulty with latch and/or effective sucking and/or the inability to latch at all for a subsequent breastfeed, as an example of retroactive interference in breastfeeding skills from the sensory-perceptual-motor learning experience with an artificial nipple.  Lactation consultants and other infant feeding specialists are frequently asked to assist nursing dyads in uncomplicated as well as complex motor learning for infant feeding, including newly acquired breastfeeding difficulties that follow the infant's learning experience with an artificial nipple.   

     Many other babies are able to achieve and sustain the latch at the breast following a learning experience with an artificial nipple, but continue to perseverate(21) with a shallow latch at the nipple-areolar complex by displaying the shallow latch technique that must be used with an artificial nipple, in contrast to the optimal deep latch with a wide open gape well onto the areola (the wide gape so often displayed by youngest newborns very soon after birth).  Such perseverating motor behavior has frequent and well-known repercussions:  a shallow latch has long been correlated with nipple pain and visible nipple damage; maternal depression has been associated with nipple pain(22); mothers often cite debilitating nipple pain as rationale for early cessation of the entire breastfeeding course; nipple damage is a risk factor for mastitis; and untreated or inadequately treated mastitis is a risk factor for breast abscess.

     Further, clinicians are educated and trained that a deep latch is the ideal oral grasp technique for adequate and efficient transfer of milk by the baby, in support of optimal weight gain in the infant.  A shallow latch is a risk factor for low transfer of milk by the baby, and when the infant perseverates with a shallow latch, the maternal milk supply can be compromised due to inadequate emptying that stimulates only partial refill, a risk factor for low milk supply.  Until infants become skilled in feeding effectively from the breast, mothers require education and support in how to otherwise build and support an abundant milk supply by frequent draining of the breast, which stimulates frequent refill toward a robust milk supply. 

     Much learning is reward-based associative learning(23), in which we learn to associate an action or experience with a pleasant or desired outcome, as in the newborn who associates the calming effects of sucking (via the hormone oxytocin) with the discovery of milk for one’s efforts, followed by the rewards of decreasing hunger and then satiety for that feeding.  We also learn by associating our actions with an unpleasant outcome, as in the baby who has returned to the breast following a bottle-feed with its immediate gravity-flow of milk, but who does not experience the immediate gravity-flow of milk from the breast with the first suck. The mammalian milk ejection reflex (MER) is not stimulated in response to gravity, but in response to the gradual rise of oxytocin, the milk-releasing hormone.  This hormonal stimulation typically elicits the initial release of milk to the infant within one to 2 minutes of beginning the feed, an important learned consequence for the baby's feeding actions, and the fastest food service on the planet at any time in the lifespan.      

     Upon returning to the breast following a bottle-feed, the baby may display the motor control to achieve the latch, suck two to three times, then release the latch and cry.  This common feeding behavior is considered by many clinicians to be a display of the baby’s frustration – often referred to as flow confusion – likely due to the lack of an immediate gravity-flow for milk release from the breast with the baby's first suck.  In addressing this infant feeding difficulty, the clinician often gives milk to the baby at the breast via feeding tube or syringe, thereby calming and encouraging the baby to continue suckling in order to stimulate the mother’s physiologic milk release.  Regardless of whether a bottle contains expressed mother’s milk, human donor milk, or artificial infant milk, the reward of an immediate gravity-flow with the first suck is quickly learned when bottle-feeding, a significant source of competition with the mother's own remarkably efficient milk ejection reflex.  This gradual but efficient rise of oxytocin is often experienced elsewhere in our humanity.  For example, there is a gradual rise of oxytocin toward the reflex of orgasm, as well as a gradual rise in oxytocin with each uterine contraction during the labor of childbirth, and oxytocin rises even during teamwork between colleagues in the workplace.  

     This feeding difficulty of “flow confusion” will surely be seen again in the preschooler who has his or her first experience with a non-functioning straw.  Typically after two to 3 sucks without the expected results (the reward for one’s efforts), the child returns the container to Mom or Dad and states, "It’s broken.” The straw may indeed be defective, or the milkshake or smoothie may be too thick to be transferred at that moment, and the parent can share their wisdom on how to address this concern.  Perhaps replacing the old straw with a new straw will solve the problem, or waiting a bit for some melting to occur will take care of the frustration. When advancing hunger or thirst is a pressing matter, stirring the drink up a bit may hasten the melting process, and happy straw-drinking can then proceed.

sensation           ∞          perception          ∞          cognition (action planning)         ∞          action (response)          ∞          consequence ∞  expected sensory consequences

     Yet it’s not possible to explain to the preverbal infant that mother’s breast provides the most rapid preparation and delivery of any food or drink he will ever experience in his lifetime.  For thousands of years at this ancient yet contemporary restaurant, the menu has included standard nutritional fare as well as immunologic daily specials tailored to the specific needs of each diner, nature’s elegant merger of kitchen/chef/server as one mother offering The Original Fast Food and The Ultimate Fine Dining Experience, one course at a time (“Just give me a minute or two, and I’ll have it right there”).  Ultrasound studies of the lactating breast show multiple MERs during any one session of milk expression, with typically three to 5 MERs per 15-minute session(24-25), similar to a 3 to 5 course meal for other members of the family, but with far more rapid service at the mother’s breast.  For the infant who is undertaking sensory-perceptual-motor learning for both breastfeeding and bottle-feeding over a close time span, the mother’s onset of milk release may very well be perceived by the infant as not fast enough or not happening at all (as observed when the infant cries at the breast), merely because it hasn’t happened yet – as compared to the gravity flow that is learned during bottled feeds.   

     Feeding confusions and feeding preferences occur across the lifespan, in spite of the adult’s vast repertoire of feeding skills.  Learning to drink from a new style of water bottle with a novel closure (cap) can be a confusing process, and requires voluntary practice for motor learning toward motor control for effective transfer of the water.   

     What is your water bottle preference?  In your impressive repertoire of drinking skills acquired over years of practice, do you prefer to drink from a water bottle by using the sports closure, which requires a particularly accurate oral grasp with strong sucking effort, or do you prefer to remove the entire cap from the bottle for a more rapid gravity-flow accompanied by less physical effort?  Perhaps your water bottle preference depends on when and why.  When out for a run, using the sports closure affords greater control during your running movements, but after the run, removing the sports cap for a more rapid quenching of thirst is the least frustrating and most gratifying way to drink.

The Exuberant Learning and Forgetting of Infancy

      Regardless of age, we humans display individual differences in learning (we are not pseudo-robots, responding to the same stimuli in the same way and at the same moment).  Babies learn faster than adults in all species studied, including humans, and the younger the infant, the faster the learning (26) and the forgetting ("the exuberant learning and forgetting of infancy").   As compared to older infants who have had repeated bottle-feeding experiences prior to practice sessions at the breast, very young infants who have used an artificial nipple may display the most rapid relearning for latch, particularly under these four conditions: 1) if the infant is in the first three days of life, 2) if the mother’s nipple is well-protracted and the areolar tissue is fairly elastic, 3) if the learning experience with an artificial nipple has been very limited, and 4) if the artificial nipple used by the infant is a pacifier rather than a bottle teat (the pacifier does not offer a reward of milk to immediately reinforce the infant’s feeding behavior).

     Nipple confusion behavior can defined as the delayed reaction time to the maternal stimuli, prolonged movement time for completion of the latch, prolonged response time, as well as an inhibition of return - the delay in responding to a previously orienting cue or stimulus. Manual guidance from the clinician in positioning and latch may be all that is needed by some newborns who are displaying nipple confusion behavior, while other babies are able to achieve and sustain the latch with the temporary support of an ultra-thin silicone nipple shield, since a nipple shield often stimulates the newborn's reflexive yet voluntary lunge toward the breast for the oral grasp.   A nipple shield provides the sensory experience of similarity to the baby, i.e., the nipple shield is similar to the greater length and firmness of an artificial nipple, and babies who have displayed nipple confusion behavior often respond more quickly to the maternal anatomy when the nipple shield is used to support the baby in his transfer of learning from the experience of bottle-feeding or pacifier use to the breast, i.e., the baby displays a faster reaction time, faster movement time, and faster response time to the maternal stimuli that has been augmented with the artificial texture and shape of the nipple shield. Finger-feeding also supports many bottle-fed babies in their transfer of learning to the breast by providing the baby with the rich sensory milieu of the mother’s skin (smell, touch, and taste) in the pairing of associates when sucking on the mother’s finger for the consequence/reward of milk.  Similarly, the use of finger-feeding supports many infants in transferring their learning from the use of a nipple shield for the oral grasp, to the ability to latch onto the breast without the support of a nipple shield.   

     Response inhibition is heavily studied in the cognitive sciences, and we must often inhibit one response in order to accomplish a different response(27-30).  When babies have had one or more learning experiences with an artificial nipple followed by a subsequent return to the breast, there is often an observable display of response inhibition of the baby’s reflexive lunging movement toward the breast for the oral grasp.  In bottle-feeding an infant, the bottle is moved toward the baby, rather than moving the baby toward the bottle (moving the baby toward the bottle would be far more difficult for the mother or other caregiver to coordinate, as compared to moving the bottle toward the baby).  This inhibition of the newborn's reflexive lunge toward the breast is yet another aspect of the newborn’s difficulty in task-switching during practice sessions in breastfeeding and bottle-feeding, and lactation consultants often assist with this difficulty by providing manual guidance to the infant in moving quickly and accurately toward the breast as the infant relearns this lunge for the oral grasp. (Imagine the difficulty in learning how to throw a ball if you’re only given practice sessions in learning how to catch the ball.)  This phenomenon of inhibition for the reflexive lunge that precedes the reflexive oral grasp at the breast is not unique to breastfed infants.  Exclusively bottle-fed infants frequently display a reflexive lunge toward the artificial nipple during early learning sessions with a bottle, but in upcoming bottle-feeding sessions as bottle-feeding movements become increasingly more controlled, bottle-fed infants display an increasing inhibition of this (unnecessary) reflexive lunge toward the artificial nipple.  

     Breastfeeding specialists spend much time in support of babies who are motor-learning how to feed in an unfettered manner without any learning interference from an artificial nipple.  In birth settings that do not yet adhere to Baby Friendly practices (as in the Ten Steps to Successful Breastfeeding[31-32] advised by WHO and UNICEF), a great deal of clinical support is also given to both members of the dyad for the acquisition and reacquisition of the baby’s oral grasp (latch) and/or effective sucking, wherever and whenever such support is available to mothers and their infants. 

     When a new mother has both breastfed and bottle-fed her newborn and subsequently utilizes a bottle-feeding position for a breastfeeding attempt, the new mother has forgotten how to hold her baby for feeding at the breast (motor forgetting).  The mother can readily relearn how to hold her infant in a breastfeeding versus bottle-feeding position, often with verbal, visual, and manual guidance from the clinician, and most importantly, the mother can relearn with the repetition of practice that is specific to the task.  Due to the presence of the primitive survival reflexes and the newborn’s lack of a feeding method repertoire at the moment of birth, as well as the phenomenon of the exuberant forgetting of infancy, the newborn faces far greater learning challenges in the acquisition of feeding skills when expected to perform task-switching for similar yet very different feeding methods during early learning.  This is frequently observed in the unequal weighting of the primitive survival reflexes for one feeding method over another, particularly during early learning when cognitive flexibility is limited, and notably limited in the young.  In contrast to the newborn’s experience, his mother already has her own robust repertoire of feeding and drinking skills as well as an immense repertoire for so very many other motor skills, learned long ago and remembered through many years of practice.

     The newborn is just beginning to learn and remember how to feed, the first of many skills learned with voluntary, reward-based practice – albeit with early support from the pre-adapted movements of the primitive survival reflexes.  Many insights into skill acquisition for infant feeding can be gathered from the integration of precepts from breastfeeding science, developmental cognitive neuroscience, and kinesiology - the study of human movement, motor learning, and motor control.  After all, one must learn to eat in order to live.

Ten Steps to Successful Breastfeeding (2018 - present)

Critical Management Procedures

1a. Comply fully with the International Code of Marketing of Breast-milk Substitutes and relevant World Health Assembly resolutions.

1b. Have a written infant feeding policy that is routinely communicated to staff and parents.

1c. Establish ongoing monitoring and data-management systems.

2. Ensure that staff have sufficient knowledge, competence and skills to support breastfeeding.

Key clinical practices

3. Discuss the importance and management of breastfeeding with pregnant women and their families.

4. Facilitate immediate and uninterrupted skin-to-skin contact and support mothers to initiate breastfeeding as soon as possible after birth.

5. Support mothers to initiate and maintain breastfeeding and manage common difficulties.

6. Do not provide breastfed newborns any food or fluids other than breast milk, unless medically indicated.

7. Enable mothers and their infants to remain together and to practise rooming-in 24 hours a day.

8. Support mothers to recognize and respond to their infants’ cues for feeding.

9. Counsel mothers on the use and risks of feeding bottles, teats and pacifiers.

10. Coordinate discharge so that parents and their infants have timely access to ongoing support and care.

Source for the Ten Steps to Successful Breastfeeding: World Health Organization, 2018.  Retrieved on April 24, 2018.  http://www.who.int/nutrition/bfhi/ten-steps/en/

Ten Steps to Successful Breastfeeding (1989 - early 2018)

1. Have a written breastfeeding policy that is routinely communicated to all health care staff.

2. Train all health care staff in skills necessary to implement this policy.

3. Inform all pregnant women about the benefits and management of breastfeeding.

4. Help mothers initiate breastfeeding within an hour of birth.

5. Show mothers how to breastfeed, and how to maintain lactation even if they should be separated from their infants.

6. Give breastfeeding newborn infants no food or drink other than breastmilk unless medically indicated.

7. Practice rooming in - that is, allow mothers and infants to remain together 24 hours per day.

8. Encourage breastfeeding on demand.

9. Give no artificial teats or pacifiers to breastfeeding infants.

10. Foster the establishment of breastfeeding support groups and refer mothers to them on discharge from the hospital or clinic.

Source for the above original language in the Ten Steps to Successful Breastfeeding, prior to the revision in early 2018:

Protecting, promoting, and supporting breastfeeding: The special role of maternity services. A joint WHO/UNICEF statement. Geneva: World Health Organization, 1989.

References

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2.  Ingram JN, Flanagan JR, Wolpert DM.  Context-dependent decay of motor memories during skill acquisition.  Current Biology 2013 June 17;23(12):1107-1112.  DOI:  10.1016/j.cub.2013.04.079

3.  Mohrbacher N, Stock J (2003).  The Breastfeeding Answer Book, 3rd revised edition.  Schaumburg IL:  La Leche League International, p. 29.

4.  Ibid., p. 30.

5.  Debas K, Carrier J, Orban P, Barakat M, Lungu O, Vandewalle G, Tahar AH, Bellec P, Karni A, Ungerleider LG, Benali H, Doyon J.  Brain plasticity related to the consolidation of motor sequence learning and motor adaptation.  PNAS 2010 October 12;107(41):17839-17844.  www.pnas.org/cgi/doi/10.1073/pnas.1013176107

6.  Seehagen S, Konrad C, Herbert JS, Schneider S.  Timely sleep facilitates declarative memory consolidation in infants.  Proceedings of the National Academy of Sciences 2015; 201414000.  DOI: 10.1073/pnas.1414000112

7.  Wilhelm I, Prehn-Kristensen A, Born J.  Sleep-dependent memory consolidation - - what can be learnt from children? Neuroscience and Biobehavioral Reviews 2012 August;36(7):1718-28.  DOI: 10.1016/j.neubiorev.2012.03.002. Epub 2012 Mar 13.

8.  Tarullo AR, Balsam PD, Fifer WP.  Sleep and infant learning.  Infant and Child Development 2011 January;20(1):35-46. 

9.  Fifer WP, Byrd DL, Kaku M, Eigsti I, Isler JR, Grose-Fifer J, Tarullo AR, Balsam PD.  Newborn infants learn during sleep.  PNAS 2010 June 1;107(22):10320-10323.

10.  Korman M, Doyon J, Doljansky D, Carrier J, Dagan Y, Karni A.  Daytime sleep condenses the time course of motor memory consolidation.  Nature Neuroscience 2007 Sep;10(9):1206-1213.  Epub 2007 August 12.  DOI:10.1038/nn1959

11.  Padmala S, Pessoa L.  Motivation versus aversive processing during perception.  Emotion 2014 April 7 [Epub ahead of print]. 

12.  Schmidt RA, Lee TD (2011).  Motor Learning and Motor Control:  A Behavioral Emphasis (5th ed.).  Champaign IL: Human Kinetics, p. 452. 

13.  Wylie G, Allport A.  Task switching and the measurement of “switch costs.”  Psychological Research 2000 August;63(3-4):212-233. 

14.  Davidson MC, Amso D, Anderson LC, Diamond A.  Development of cognitive control and executive functions from 4 to 13 years:  Evidence from manipulations of memory, inhibition, and task switching.  Neuropsychologia 2006;44(11):2037-2078.  Epub 2006 March 31. 

15. Muhmenthaler Michéle C, Meier Beat.  Task switching hurts memory encoding.  Experimental Psychology 2019;66(1):58-67.  doi: 10.1027/1618-3169/a000431

16.  Baddeley A, Eysenck MW, Anderson M (2015).  Memory (2nd ed.).  London and New York: Psychology Press, p. 245. 

17.  Castro L, Ortega N, Matute H.  Proactive interference in human predictive learning.  International Journal of Comparative Psychology 2002;15:55-58. 

18.  Dewar MT, Cowan N, Sala SD.  Forgetting due to retroactive interference:  A fusion of early insights into everyday forgetting and recent research on anterograde amnesia.  Cortex 2007 July;43(5):616-634. 

19.  Rossi-George A, Rovee-Collier C.  Retroactive interference in 3-month-old infants.  Developmental Psychobiology 1999;35:167-177.

20.  Neifert M, Lawrence R, Seacat J.  Nipple confusion: Toward a formal definition.  The Journal of Pediatrics June 1995;126(6):S125-S129. 

21.  Glover S, Dixon P.  Perseveration effects of reaching and grasping rely on motor priming and not perception.  Experimental Brain Research 2013 Apr;226(1):53-61.  DOI: 10.1007/s00221-013-3410-y.  Epub 2013 Jan 26.  

22.  Amir LH, Dennerstein L, Garland SM, Fisher J, Farish SJ.  Psychological aspects of nipple pain in lactating women.  Journal of Psychosomatic Obstetrics and Gynaecology 1996;17:53-58. 

23.  Giles A, Rovee-Collier C.  Infant long-term memory for associations formed during mere exposure.  Infant Behavior and Development 2011 Apr:34(2):327-338. DOI:  10.1016/j.infbeh.2011.02.004.  Epub 2011 April 6.  

24.  Ramsay DT, Kent JC, Hartmann RL, Hartmann PE.  Anatomy of the lactating human breast redefined with ultrasound imaging.  Journal of Anatomy 2005;206:525-534.

25.  Gardner H, Kent JC, Lai CT, Mitoulas LR, Cregan MD, Hartmann PE, Geddes DT.  Milk ejection patterns:  An intra-individual comparison of breastfeeding and pumping.  BMC Pregnancy & Childbirth 2015 July 30;15:156.  DOI: 10.1186/s12884-015-0583-3 

26.  Rovee-Collier C, Giles A.  Why a neuromaturational model of memory fails: Exuberant learning in early infancy.  Behavioural Processes 2010;83:197-206.

27.  Wright A, Diamond A.  An effect of inhibitory load in children while keeping working memory load constant.  Frontiers in Psychology 2014 March 14;5:213.  DOI:  10.3389/fpsyg.2014.00213.  eCollection 2014.  PMID: 24672502 [PubMed]

28.  Aquili L, Liu AW, Shindou M, Shindou T, Wickens JR.  Behavioral flexibility is increased by optogenetic inhibition of neurons in the nucleus accumbens shell during specific time segments.  Learning & Memory 2014;21:223-231.  DOI: 10.1101/lm.034199.113

29.  Simpson A, Riggs KJ, Beck SR, Gorniak SL, Wu Y, Abbott D, Diamond A.  Refining the understanding of inhibitory processes:  How response prepotency is created and overcome.  Developmental Science 2012 Jan;15(1):62-73.  DOI:  10.1111/j.1467-7687.2011.01105.x.  Epub 2011 Nov 28.  PMID:  22251293 [PubMed – indexed for MEDLINE]

30.  Shing YL, Lindenberger U, Diamond A, Li SC, Davidson MC.  Memory maintenance and inhibitory control differentiate from early childhood to adolescence.  Developmental Neuropsychology 2010;35(6):679-697.  DOI:  10.1080/87565641.2010.508546.  PMID: 21038160 [PubMed – indexed for MEDLINE]

31.  World Health Organization (2018).  Ten Steps to Successful Breastfeeding.  Source: Protecting, promoting, and supporting breastfeeding.  The special role of maternity services.  A joint WHO/UNICEF statement.  Geneva: World Health Organization.  http://www.who.int/nutrition/bfhi/ten-steps/en/

32.  http://www.who.int/nutrition/bfhi/ten-steps/en/

For More Information

Some texts on learning and memory, including sensory-perceptual-motor learning: 

Baddeley A, Eysenck MW, Anderson MC (2020).  Memory (3rd ed.).  Abington, Oxon; New York, NY: Routledge.

Breedlove MS, Watson NV (2013).  Biological Psychology:  An Introduction to Behavioral, Cognitive, and Clinical Neuroscience (7th ed.).  Sunderland, Massachusetts USA:  Sinauer Associates, Inc.  

Coker C (2021).  Motor Learning and Control (5th ed.). Abington, Oxon; New York, NY: Routledge.

Courage ML, Cowan N, Eds (2022). The Development of Memory in Infancy and Childhood (3rd ed.). Abington, Oxon; New York, NY: Routledge.

Goodway JD, Ozmun JC, Gallahue DL (2021).  Understanding Motor Development: Infants, Children, Adolescents, Adults (8th ed.).  Burlington, Massachusetts: Jones & Bartlett Learning.    

Kalat JW (2019).  Biological Psychology (13th ed.).  Boston, Massachusetts USA: Cengage Learning.  

Kandel ER, Dudai Y, Mayford M, Eds (2016). Learning and Memory. Cold Spring Harbor, New York USA: Cold Spring Harbor Laboratory Press.

Schmidt RA, Lee TD, Winstein CJ, Wulf G, Zelaznik HN (2019).  Motor Control and Learning: A Behavioral Emphasis (6th ed.).  Champaign, Illinois USA: Human Kinetics.    

Walker M (2017). Why We Sleep: Unlocking the Power of Sleep and Dreams. New York: Scribner.

A memoir by Nobel Laureate Eric Kandel:

Kandel ER (2006).  In Search of Memory:  The Emergence of a New Science of Mind.  New York NY:  W.W. Norton & Company, Inc. 

© Debra Swank 2015 - 2024.  The author can be reached at info@morethanreflexes.org. This article may be copied and shared when the author's name and copyright are included with the article.   

A video from Yuko Munakata on task-switching and perseveration with Piaget’s A-not-B error task: