New parents quickly learn that “eat, play, sleep” is the broad structure that should guide a newborn’s days. I have already discussed eating and sleeping, which are two sides of the same coin, because playing with a baby is not really possible in the first eight-ish weeks. Not only are babies that young hardly interactive, getting babies to sleep is so time consuming that playing would leave little time for actual baby sleep time before the next feeding.
Once my wife and I could start playing with Raya more, parenting became a lot more fun. When the baby can follow movement with its eyes, start to rotate its head, and realize that its hands are connected to arms that it controls, the world opens up. For me, this period is when the baby finally became human, and it is when parenting started to become enjoyable.
Playing with your baby is one of the best parts of having a kid. Watching them observe the world around them, learn to use their neck, explore their hands, roll over, and so on is very rewarding, especially because there is often quick feedback from our input as parents. For example, my wife and I felt like our baby was not developing its neck muscles quickly enough. (Okay, we were concerned because the babies at our parenting class had more neck control, and by concerned I mainly mean embarrassed.) We then increased the frequency of her tummy time, and within three days we were no longer concerned about her neck development.
At the same time, play time can be very monotonous. There are only so many toys to use, and there are so many ways to use them; a video game or good book they are not. There are only so many directions in which to move high contrast images, songs to sing, toys to dangle in front of their face, and noises to make to get their attention. Perhaps many people enjoy repeating the same three to five interactions for 20-40 minutes several times per day. I am not one of them. I found I could only stay engaged for about 10 minutes per session and enjoyed the morning ones much more than ones later in the day.
By now, it should therefore not surprise you, dear reader, to learn that parts of it, however, struck me as excessive, or at least more energy consuming than my ideal, and I therefore started to learn more about just how important play is for baby development. Not wanting to be bored out of my mind but also not wanting to lower the ceiling of my baby’s potential are goals in tension with each other. I therefore started to ask myself questions such as: do I need to actively provide my baby stimulation all the time? If I do not, am I giving it worse visual and muscular development? Will my child be bad at sports or driving because I spent 5 minutes on my phone instead of waving a fourth toy in front of it? By now, it should therefore not surprise you, dear reader, that I turned to the academic literature for answers to these questions, and I was not surprised to find there are no good answers to these questions.
There are three parts of playtime that I explored. First, do I have to be involved in every minute of stimulation? Will the baby be fine if I read a book or do some light work while it explores its hands, puts a toy in its mouth, or explores the world from its belly? In other words, it is not clear to me that the direct stimulation parents provide help a baby develop more than the stimulation of existing, of simply observing the immense novelty that surrounds that. Second, even if parental stimulation has value add, does that benefit come from the use of toys or something else? While my baby clearly follows high contrast cards and likes putting toys in her mouth, it is not clear that I had to spend money to give her that stimulation. Perhaps anything would capture her attention; I know she would put anything in her mouth. In other words, many of the toys seem superfluous, a way to get parents to part with money more than anything else. Third, does stimulation at such a young age affect later developmental outcomes? For example, it makes sense that training a young kid in an instrument or sport will improve those skills, but parents do not start training three-month old babies in piano or basketball. There are clear impacts to not feeding or holding a newborn enough, so it could be there
Before trying to answer these questions, I need to clarify three issues. First, by stimulation I mean active adult engagement designed to build physical skills via neurological development. Talking to a kid is stimulation while putting them in front of an iPad is not; using high contrast cards to encourage eye focus and neck movement is stimulation while setting the baby on the ground is not. The key in these examples and my definition of stimulation is the active engagement of the parent, the demand that the caregiver’s primary locus of attention is the child. Second is age: I am interested here on very young kids, certainly closer to newborns than to toddlers, the age when every day holds the promise of a new development. In other words, I am not contesting deliberate practice type challenges parents give their children: whether or not providing a 5-year-old with books improves their reading or if early dedication to competitive endeavors like chess or sports makes a kid more likely to succeed. I want to know whether or not spending dozens of minutes per day with my newborn is better than slacking off some and letting my baby entertain itself.
Finally, I want to emphasize that I enjoy the stimulation time I give to my child and am not trying to absolve myself of parenting. In line with “breast is best” and similar platitudes, parents are encouraged to give their newborn a variety of stimulation. Rather, it feels to me like society imposes huge pressure on parents to do the Right Thing for their kid so that their kid is happy and healthy. I want to talk with my kid in baby talk, but I do not want to feel like a bad parent if I get bored after three minutes. I want to see my kid swivel its head to follow an object, but I do not want to feel anxious if I am not using the right set of fancy high contrast cards. I want to see my kid excel at tummy time, but I do not want to worry about future poor athletic performance if they do not spend the ordained amount of time in that position a few times.
There are two reasons, one biological and the second cultural, to doubt that constant caregiver stimulation is required for infants to develop proper visual and motor skills.
The primary reason to be skeptical of advice which insists on the primacy of adult-led play is that the development of eyesight and muscle control has strong biological bases. For both, a baby’s skill cannot outpace the development of the specific brain regions and neuron connections (how brain cells are linked to each other). Caregiver stimulation can there only affect a new skill’s development once that part of the brain is established. The extent to which caregiver stimulation affects visual and motor development therefore depends on how much each is governed by natural brain development.
Motor development is largely biological. This regularity is because motor control is directly tied to brain development. Neurons develop and mature starting in the spinal chord, then up through the brain stem, the primary motor cortex, and later motor areas in the frontal lobe. This upward maturation is reflected in babies’ motor development progressing from its core and neck out through their limbs and into hands and feet. These stages of brain development are reflected outwardly in the top-down, in-out development of babies’ actions: first head control, then torso, then gross arm and leg control, then fine motor control like gripping and pinching. In other words, a 3-month-old baby is never going to smoothly reach for, hold, and manipulate a black and white card because the neurons in its brain that are needed for that do not exist. Any stimulation designed to develop a skill for which there is no neural substrate is therefore stimulation that will not “work”, regardless of how much fun it is.
Studies of twins repeatedly find evidence for the primacy of genetics in motor control development. The canonical example here is M.B. McGraw’s 1943 book The neuromuscular maturation of the human infant, where the author documents that extensively training a twin in movement skills does not cause it to acquire that skill earlier than its identical twin. “Genetic analysis of motor milestones attainment in early childhood” by Inga Peter, Michael Vainder, and Gregory Livshits (Twin Research 1999) shows that the onset of new motor skills is most correlated in identical twins and then fraternal twins in comparison to the onset timing when comparing babies to their older siblings. The consistency of motor development leads Lise Eliot, a Professor of Neuroscience at Rosalind Franklin University of Medicine and Science, the author of What’s Going on in There? How the Brain and Mind Develop in the First Five Years of Life, and the source of all my above knowledge, to state:
From a researcher’s point of view, the most striking thing about motor development is its predictability. Virtually every baby, from virtually every culture, acquires the same fine and gross motor skills in the same consistent sequence. Different babies do vary, of course, […] Nonetheless, on average, healthy babies of all cultures achieve the same motor milestones at just about the same time.
Parental behaviors can affect the pace and order of motor development, but again they do not so in any major way that causes long-term differences. For example, babies put to sleep on their back develop arm and neck control a few weeks later than babies that start off sleeping on their stomach. Babies sleeping on their back are much less likely to die from SIDS, and no studies have found long-term developmental delays of back sleepers, so the slight delay is a reasonable price to pay for safety. Similarly, babies raised in settings where parents gather food or tend fields sit and walk several weeks in advance of those raised in “modern” ones.
One way to make this argument is via comparison with another source of parenting stress: sleeping. (What follows is a summary of research identified by “The science of healthy baby sleep”, an excellent BBC article about sleep training.) Within countries, children have divergent sleep patterns, both in terms of when they go to sleep and for how long they sleep (Price, Anna M.H. et al. 2013, “Children’s sleep patterns from 0 to 9 years: Australian population longitudinal study” in Archives of Disease in Childhood). A 2017 study of baby and mother sleep across the Middle East – “Young child and maternal sleep in the Middle East” in Sleep Medicine – finds that babies there report later sleep and wake times than European and Asian babies, and a higher percentage of mothers report sleep issues for themselves and their babies. A survey of 29,287 infants’ sleep in predominantly Asian and predominantly Caucasian countries finds the former have later, shorter sleep times and more frequent reports of sleeping troubles (Mindell, Joan A. et al, 2010. “Cross-cultural differences in infant and toddler sleep between Asian and Western countries” in Sleep Medicine).
Two studies of American parenting really emphasize the contingent nature of parenting advice. “Getting the Baby on a Schedule: Dutch and American Mothers’ Ethnotheories and the Establishment of Diurnal Rhythms in Early Infancy” is a 2020 book chapter by Saskia D.M. van Schaik and coauthors that uses participant observation of 41 American moms and 33 Dutch ones to contrast parenting styles. American mothers report letting the baby lead its sleep development while Dutch mothers more actively guide their children using the “three Rs”: rest (rust), regularity (regelmaat), and cleanliness (reinheid). Jennifer G. Rosier and Tracy Cassels’ “From ‘Crying Expands the Lungs’ to ‘You’re Going to Spoil That Baby’: How the Cry-It-Out Method Became Authoritative Knowledge” (2021, Journal of Family Issues) documents how America’s dominant approach to sleep training change at the turn of the 20th century. Before widespread knowledge of communicable diseases and widespread industrialization, parenting guides did not even mention sleep, likely because adult sleep was rarely regimented into one long block like it is now. In 1892, a leading doctor, Dr. Emmett Holt, introduced the phrase “cry it out” and proscribed parental behavior. Variants of this advice then percolated for decades until Drs. Richard Ferber and Marc Weissbluth introduced their sleep training manuals in the mid-1980s. In other words, Americans’ dominant approach to putting their babies to sleep has changed dramatically over the past 200 years.
I could find no equivalent studies of stimulus, but I would not be surprised if attitudes have similarly changed. To believe that society’s current approach to stimulus is the one Truth therefore means that one believes previous approaches created less capable adults than was otherwise possible. While we will never know the counterfactual – what would society look like if babies were exhaustingly stimulated for centuries? – it seems like everything has worked out okay. Would commercial aviation have arisen before World War II if the Wright Brothers had high contrast cards to play with? Would someone before Darwin figured out evolution if they had colorful objects waved in front of them? Maybe, but probably not. The point is that approaches to stimulus, and childcare more broadly, are ever changing, yet humanity has somehow survived. If there were clear, strong reasons to provide one type or amount of stimulus over another, then humans would have figured it out by now. That the same culture at different times, much less different cultures at the same time, has different beliefs about childraising suggests that approaches to parenting are grounded less in data and facts and more in beliefs and norms.
Once I realized how fluid parenting advice is, I naturally wondered if babies even respond to caregiver-led stimulation. Since to the new human everything is novel and therefore stimulative, it is not immediately obvious that toys provide extra. (For the rest of this subsection, I am focused on visual stimulation.) For example, the Lamaze Freddie the Firefly is a great toy: it has tons of different textures, colors, and shapes for babies to explore, and its light weight makes it easy for young kids to hold and explore on their own. My wife and I love using it with our kid. However, I was not convinced it holds her attention more than waving something else in here face. To convince myself, I therefore ran a small experiment and analyzed the results. If different types of objects commanded different amounts of attention from my little girl, then that result would suggest stimulation stimulates.
To study if toys designed to stimulate stimulate, I devised a simple experiment with my child. During each play session, I would select one of four objects: a high-contrast black and white card designed to attract her attention, a colorful soft plastic toy designed to be grabbed (not designed for visual development), a paper coaster we already owned recreating North Vietnamese propaganda, and my hand. The card came with the Lovevery Play Gym, but we also have the Wee Gallery Art Cards. High contrast cards are designed explicitly on the premise, which I believe is grounded in biology, that infants have the easiest time following them; they should therefore be the most stimulative. (I used the same card, a spiral pattern, from a set of cards with different patterns.) Since this card – these cards – are specifically designed to stimulate the baby’s visual attention, they should actually do so when pitted against the other three objects.
The toy is the Manhattan Toy Company Winkel. It contains loops of bright orange, yellow, green, and red, creating lots of contrast from all viewing angles. Though it is marketed for teething because it can be refrigerated and is very easy for a baby just developing hand control to grip, its multiple contrasting colors are also great at stimulating eyes. I have to believe the color choices were intentional, but since the toy is firstly meant for teething, I expect it to hold the baby’s attention for less time than the black and white high contrast cards.
The coaster is exactly that, a compressed paper square object designed to protect furniture from beverages’ condensation. Usefully for this experiment, however, is that its design recreates a North Vietnamese propaganda poster showing an American B-52 bomber crashing after being intercepted by fighter jets. In other words, it has lots of bright, high contrast colors separated by sharp lines. (I bought several coasters like this on a vacation in Vietnam. They are from Artbook, a leading Vietnamese book distributor with several stores across the country. The Ho Chi Minh one has the most items for a foreign audience.) I chose it because its design should have a very similar effect as the Winkel and Lovevery objects, but it is an everyday household object not designed for baby stimulation. Its inclusion therefore lets me examine whether one needs to buy toys designed for stimulation or instead use baby safe household objects and save the money. I hoped it would be at least as stimulating as the baby toys but would not have been surprised if it was less.
Finally, the hand is 35 years old, callused, and between pale and tan color. The hand is neither high contrast nor colorful, but it should interest the baby’s eyes because it moves. Including it serves as the placebo treatment: if newborns are responding to movement and not contrast, then it should hold my kid’s attention just as much as the other three objects. If the baby is actually responding to bright colors and contrast, then the hand should hold her attention the least.
Moreover, the selection was random, removing any potential bias relying on my decision making could introduce. (Randomness comes via R, a programming language common in data science, specifically its sample()function to choose one of the four objects to test.) For example, it could be that a child has more energy at the start of the play session than the end, so the first object presented would receive more engagement than the last. Seeing this pattern, one may be tempted to start a session with an object that does not seem to otherwise hold the baby’s attention. Not only would my behavior then make the stimulative effect of the object appear stronger than it truly is, the final dataset would have too many observations of that object and not enough of the other three. In fact, researchers have repeatedly shown that humans are not good at generating random sequences of numbers. When research subjects are asked to generate random sequences of numbers, those sequences do not have enough long sequences of the same number because randomness is commonly thought of as lack of repetition (Schulz, Schmalbach, Brugger, and Witt 2012, “Analysing Humanly Generated Random Numbers Sequences: A Pattern-Based Approach”). If I were to choose the order of presenting objects, this bias would likely cause me to not show the same object consecutively, much less three or four times in a row. However, some objects may hold the baby’s attention across viewings longer than others; if the strength of this attention holding differs for each object, then not showing objects several times in a row will increase the estimated stimulation from some objects and decrease it for others. By randomly choosing the object to use for stimulation, I did not have to worry about my behavior influencing the results.
After choosing the object, I held it approximately 8” from her face and moved it side to side, tracking for how many times she rotated her neck to follow the object as I moved it towards the ground. Each rotation of the head back to facing the ceiling would count once, and the total number of rotations back is the outcome of interest. A more stimulating object should have a higher average number of rotations, a less stimulating one fewer. The original research design was to repeat this process three times per play session for ten days, with a goal of 120 total tests. On the fifth day, after the 13th session and 39th test, I added the Artbook coaster. I realized that one of the objects was clearly less stimulating than the other two, so I added the coaster to have a second non-toy object. I should have thrown out all the tests before adding the coaster, but I did not because the tests crowded out other playtime activities. Just as importantly, I did not want to run more tests because raising a baby is exhausting and it would have been too painful to throw away data. In addition to the object type and number of rotations, I tracked the date, time of day, play session of day, test number of the session, and included a notes column for any qualitative observations.
If the four objects have the same average number of rotations, then none are more stimulative than the other. Since one of the objects is my hand, a lack of difference would suggest that the toys and coaster do not stimulate more than anything else, i.e. that they do not need to be purchased for their stimulative effect. If, however, the objects do have different effects, then the average number of rotations will differ. Given the purposes and design features of the objects, I expect the high contrast black and white card to have the highest average number of rotations, followed by the teething toy, coaster, and hand in that order.
Figure 1 shows the results from this experiment. The x-axis is the number of head rotations, the measure of engagement, and the y-axis is the percentage of times the baby moved her head for each number of rotations. The results are also grouped and colored by object type. For example, the peak of number of observations for my hand is 1, and the wider range of x-axis values for the card and coaster mean there almost as many times that the baby was very interested in them as not. There is a clear ranking of preferences here: the hand is the least interesting, the Winkel toy is the next most interesting, and the card and coaster are equally interesting.
|Figure 1: Clear Preferences for Certain Objects|
These results differ from my expectations. The biggest surprise was how uninteresting my hand is. I thought movement would generate some interest and I even wiggled my fingers to keep my baby’s attention, but she just was not interested in my hand. That she was more interested in the other three objects suggests that bright colors do cause greater interest. I was then surprised to find the toy less interesting than the other two objects since it is made of high contrast colors. Perhaps the difference is that the baby knows the toy from other contexts, so it is less interesting than the card and coaster which were primarily used for the experiment. It may also be that the way the Winkel is designed means lots of white from the ceiling is also part of the baby’s vision when looking at it, and this white may be less interesting, just like my hand. The other surprise to my skeptical mind is that the high contrast card does work. Even though it is only black and white, my baby loved looking at it. Many of the trials were even stopped because she grabbed at the card, and I could not resist letting her have it after trying to hard. So, babies do love looking at high contrast cards.
My skeptical mind was right about one thing, however: one does not need to buy a special toy to stimulate the baby’s visual attention. That the coaster causes just as many head turns as the card suggests that what really drives attention is high contrast colors, not black and white cards. This result is important because it means you only have to find high contrast objects you have laying around the house to keep your baby entertained. After seeing this result, I started presenting my baby with magazine pages, especially the crossword, and towels with bright patterns. She loved those too. So, if you are debating whether or not to buy the high contrast cards, rest comfortable knowing you do not. Buy them if you want to, not because you have to to be a good parent.
This research design and results are adequate to satisfy my curiosity, but there are several areas that need improvement if I were conducting an academic study. Most importantly, I need more babies to ensure that any finding is not because of my child’s preferences. To make sure any differences are not then driven by the baby’s home environment, I would bring them into a lab setting so they face the same noises, colors, and so on. While differing home environments only matter if they are not randomly distributed across the babies, it is very difficult to know if they are. This difficulty means results could be driven by unmeasured variables that correlate with how parents show the four objects, so the safe approach is to put babies in the same setting. It would also be informative to start babies younger than twelve weeks of age, which is how old my daughter was when I started the experiment. Starting younger babies can show if the objects’ effects change over time. It could be the case, for example, that the high contrast cards are most effective at 4 weeks of age but are no longer more stimulative than other objects as a baby’s eyesight improves. (Since babies have weak immune systems, I would wait until either their first round of vaccines or conduct all tests outside.) I would also use only trained staff to wave the objects and record the number of head rotations. That way, the babies will not be following cues from their parents and there is no risk that self-reporting inflates numbers. This uniformity of setting ensures that any resulting differences in average number of rotations per object is due solely to the object and nothing else.
Even if there is a difference in short-term stimulation from the objects, what I think parents are really interested in – at least what I am interested in – is whether this stimulation has long-term effects. That is, will my baby have better eyesight if I use the right toys? Will it have more coordination if it gets to explore different textures? If I play with it for 20 minutes, will it love me more than if I play with it for 10? The answers to the short-term questions tell us what toys to buy or not, but the long-term outcomes are what we have to live with.
To answer the second set of questions about the long-term effects of stimulation would require two modifications. First, I would need a tool to measure long-term effects. The most common approach in this situation is to send follow-up surveys to parents at equally spaced durations and ask questions about any long-term outcomes of interest. (With more effort, one could use administrative or medical records.) Second, babies during the experiment would need to receive stimulation from only one of the four objects; the randomness would then move from choosing which of the four objects to show for each test to which of the four to show for all tests. If a baby in an experiment is exposed to equal amounts of each object, which is what the randomness in the first research design ensures, then on average it will have the same long-term vision outcomes as the other babies. It would therefore not be possible to tell which of the toys, if any, cause any differences in long-term outcomes. After a few waves of these surveys, it could be possible to see if there are any long-term differences in outcomes.
The basic answer is almost certainly that slacking off in stimulation has no long-term negative consequences on the child’s development, for three reasons. First and most importantly, the entire world stimulates newborns. A newborn has never seen other humans, lights, walls, blankets, and so on, literally everything in the world. Even when seeing these new objects for the first time, a newborn does not yet have the mental capacity to recognize them as external objects with which they can interact in some type of relation with their own body. In fact, a newborn’s own body is new to them, as every parent learns when their child starts staring at its hands, then sucking them, and eventually doing the same with the rest of its reachable body. This curiosity eventually extends to nearby objects, and far away ones once mobility comes. The act of exploring literally stimulates new brain development, and this stimulation engenders further development.
Since to the new human everything is new and therefore stimulative, it is unclear how much extra enrichment is provided via active adult engagement. If a baby does not have a caregiver burbling in front of it, it will instead notice other sounds like passing cars or loud neighbors. If it does not have high contrast cards to focus on, it will look at a face or wall objects. If it does not have a crinkly toy to explore, it will explore its hands and feet. In other words, there is plenty of stimulation to be had without toys or adult engagement.
Second, slacking off in terms of purchasing toys is not a problem so long as there are alternative objects that can stimulate the baby. This is the conclusion that I reached from the experiment I ran using four toys.
Third, there is very very little research on infant stimulation and long-term outcomes. A 2018 paper by Karla Holmboe and coauthors (“Longitudinal development of attention and inhibitory control during the first year of life”, Developmental Science) investigates whether training infants in attention tasks causes them to perform better on inhibitory control tasks several months later. It does not: stimulus may not even have short-term effects! “Training Attentional Control in Infancy” in Current Biology (2011) by Sam Wass, Kaska Porayska-Pomsta, and Mark H. Johnson reports the results of training 11-month old children in attentional control tasks. After three sessions of providing infants on screen stimulation designed to increase the duration of infants’ engagement with subsequent tasks, the 21 that received training outperformed the 21 who did not. As the authors note, however, assessment was conducted only 15 days after the final training task, so the study only shows that infants can be trained, not that that training has long-term effects. “Do Babies Learn From Baby Media?” (Judy S. DeLoache, Katherine O’Doherty, et al. 2010, Psychological Science) evaluates whether 12-18 month old babies learn vocabulary from educational DVDs. They do not, and the babies that learn the most are those whose parents teach them words during everyday activities. Executives at baby DVD companies, fret not: parents who use the DVDs believe that their kids learn more words than they actually do.
Some studies do find correlations between infant performance on cognitive tasks and later performance as toddlers. While there does not appear to be a consistent set of activities that exhibit this correlation, i.e. it is not clear why some effects persist while others do not, studies usually stop around ages 3 to 4. As Alexandra Hendry, Mark H. Johnson, and Karla Holmboe explain in a 2019 Annual Review of Developmental Psychology, any effects are likely to be small, detecting small effects requires large samples, and collecting large samples (experimenting on a lot of children) is difficult. Susan A. Rose, Judith F. Feldman, and Jeffery J. Jankowski report in a 2012 article (“Implications of Infant Cognition for Executive Functions at Age 11” in Psychological Science) that information processing capabilities in infants and toddlers correlates with executive function at age 11. This finding suggests long-term correlations, but the researchers did not perform any interventions on the infants or toddlers: the key finding is that there is persistence, but the researchers are not able to say what causes the initial difference. While one should never bet against researcher ingenuity, for the time being there is little evidence to suggest that stimulation improves later outcomes in a way that affects the child’s well-being.
I emphasized that last clause to stress that babies who receive sustained stimulation could outperform much later in life babies that do not. This outperformance would be minor and for behaviors that do not affect its ability to be a successful member of society. For example, maybe a baby with parents who dutifully show it high contrast cards for hours per day will find Waldo more quickly or have a greater appreciation of color, but those abilities are unrelated to whether or not it says thank you, treats others with kindness, or tips well. A baby that learns to sit three weeks earlier than another baby may become a more confident walker, but early sitting does not mean it will be a better friend or more courteous roommate. Even if there are long-term differences due to stimulation, they are almost certainly not for outcomes that truly matter.
Finally, Rosier and Cassels’ article about the emergence of the cry it out paradigm is relevant here as well. Early proponents of cry it out, John Watson and his wife, wrote a 1928 book advising parents to withhold affection so that their children would become independent and self-sufficient. (How cruel!) They were soon attacked for “advice that was not backed up by well thought out ideas”, and a 1994 article would point out that the book gave “advice beyond data”. (This quote is from the Rosier and Cassels article.) Some things never change!
It has taken me two months to write this post because caregiving takes more and more time as a baby grows, and UCLA’s academic year started. In that time, my daughter’s eyesight and muscle control have developed remarkably. She can see my wife and I from a distance and respond to our movement when that far away, shows preferences for certain colors and toys, rotates toys to see them from different angles, switches toys between hands, gets bored of toys (meaning she recognizes them), and, my favorite, is so quick to grab my face and hair when I go to kiss her belly that I have to assume she will catch me when I do. In other words, she is developing perfectly normally.
In researching this post, it became clear to me that the only way my wife and I could harm our baby is via neglect. Leaving her alone for long stretches for days or weeks at a time, not responding to her cries or gestures, always keeping her in a crib or car seat, or never taking her out of one room – these are some neglectful behaviors that could permanently affect her development. Neglect is a high bar. Taking two minutes to go to the bathroom or check e-mail, not constantly buying her new toys or talking to her, or only knowing three nursery rhymes – these are normal behaviors and will not affect anyone’s child in any permanent way.
The answer, then, to my exhausted query when stimulation started is to relax and enjoy the process as much as possible. Some days, stimulation means my daughter wants 15 uninterrupted minutes with Freddie the fly or Sophie the giraffe. Other days, it means sucking her thumb or my fingers for a long time. Often, her preferred stimulus is verbalizing with us and physically exploring our bodies – touching our faces, caressing my leg hair, or sitting in our laps. Recently, as she has gained core control, stimulation means sitting in a highchair while we eat or carve a pumpkin. While specific parental behaviors can hasten babies’ attainment of visual and muscular milestones, that attainment has zero impact on said baby’s future capabilities or well-being. The whole world stimulates babies, and as long as parents expose their kids to it, their eyesight and muscular control will come along fine.
 Well, for the sanity of parents everywhere, let us hope not!
 The Dutch emphasis on the three Rs also did not become prominent until 1907.
 It would be interesting to have a condition where no object is shown to the baby but its head rotations are counted. Since this wrinkle would require a completely different way of measuring the outcome and is equivalent to a parent providing no stimulation, I do not think it is necessary.
 For ethical reasons, I would not conduct the long-term experiment. As I discuss later, ethical concerns are, rightfully so, a major reason there are few parenting studies.