The learning of all feeding and drinking skills across the lifespan are forms of reward-based learning and reinforcement learning, both of which have been studied in the cognitive sciences for many decades.
There are indeed some babies who display little difficulty in task-switching between breastfeeding and bottle-feeding, and the minimal difficulty is often displayed as minimal but nevertheless prolonged rooting (sensory processing in identifying the stimulus/stimuli, followed by action planning) prior to achieving the oral grasp for either or both feeding methods. This can be measured in milliseconds as response time, which is comprised of both reaction time and movement time for achieving the task, as in achieving and sustaining the oral grasp for milk-feeding.
Task-switching has long been studied in the cognitive sciences, and today's PubMed search using the term task switching has yielded 2,888 results. However, if using the term with a hyphen as task-switching, the search yielded only 1,321 results. Switch costs of task-switching are measured as decreased speed and accuracy for the task, measured in milliseconds. Infant feeding specialists, such as IBCLCs and others, are often called upon to provide manual guidance to the infant toward re-learning the oral grasp and/or effective suckling after a learning experience with an artificial nipple.
I have an untested two-part hypothesis in regard to why a number of babies are able to successfully switch back and forth from breast to bottle and back to breast again, given that so very many infants display challenges ranging from mild to moderate to pronounced difficulties in correctly performing such task-switching skills, particularly during early learning, but not only during early learning. This hypothesis applies to conditions of learning in the absence of learning constraints, such as complete cleft of the lip and palate; non-protractile nipple anatomy; and pronounced breast engorgement, however transient.
Part 1 of the hypothesis: By following Step 9 of the Ten Steps and thereby building motor memory for the oral grasp and effective suckling at the breast, babies are able to strengthen motor memories for latch and suckling at the breast to a more robust state of motor memory. Step 9 of the Ten Steps to Successful Breastfeeding encourages this accommodation for infants who are just beginning to learn, by advising, "Give no pacifiers or artificial nipples to breastfeeding infants."
Consolidation is the building and strengthening of memory into a robust state, and this includes the consolidation of motor memory. Early memories are fragile, and require the repetition of practice as well as sleep in building robust memory. Aside from the fragility of early motor memories, consider the fragility of other early memories, such as the difficulty in remembering a new computer password until more frequent use (the repetition of task-specific practice) builds increasingly robust memory for that new password.
The second part of my untested hypothesis follows in regard to why some babies are able to switch back and forth between breast and bottle with only minimal delays in achieving the oral grasp following a moment or two of prolonged rooting.
When babies are able to both breast and bottle-feed with no greater difficulty during task-switching other than minimal rooting prior to achieving and sustaining the oral grasp, I suspect and hypothesize that these babies are at a particular breast (and brain!) that is being stimulated for a far more rapid onset of the initial MER than average, which is a rapid reward to the infant in reinforcing what is being learned (rapid onset of the initial MER is not to be confused with an overactive MER that lasts throughout most or much of a feed). This hypothesis is not a new lightning bolt of realization, but an integration of precepts from breastfeeding science and the cognitive sciences. Clinicians have long discussed flow confusion and flow preferences, in addition to nipple confusion, nipple preference, suck confusion, and suck preference.
When babies learn how to bottle-feed, regardless of whether the bottled milk is their own mother's milk, human donor milk, or artificial infant milk, the positive reinforcement to the infant of learning how to use correct bottle-feeding movements is the infant's ability to obtain milk with the very first suck via gravity flow, even when paced bottle-feeding is ideally used for a bottled feed. The Milk Ejection Reflex (MER) is not stimulated by gravity, which is ideal from the milk-giver's point of view. While lactating, who would wish to constantly release milk via gravity, except when adopting a supine position ?
When we’re no longer at the breast and have transitioned to meals at the family table, the acquisition of all other feeding and drinking skills involves the reward and reinforcement of food or liquid with the very first correct eating and drinking movements, in spite of the awkward nature of feeding and drinking movements during earliest skill acquisition. How we move, and the sensory consequences of our movements, inform us of so much.