Episode #644

The Mouth as a Scanner: Decoding Baby Sensory Milestones

Why do babies put everything in their mouths? Explore the "sensory homunculus" and the hidden architecture of infant brain development.

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In the latest episode, Herman Poppleberry and Corn delve into the chaotic, fascinating world of infant development, specifically focusing on the seven-month mark. Using the story of a young baby named Ezra as a jumping-off point, the hosts explore why infants at this age seem determined to ingest everything in their path—from coffee table corners to handfuls of baby wipes. What looks like a lapse in health and safety protocols is actually a sophisticated neurological process. As Herman and Corn explain, these "sensory milestones" are the invisible architecture of development, transforming a baby from a passive observer of data into an active participant in reality.

The Mouth as a High-Definition Scanner

The central question of the episode revolves around oral exploration. Why is the mouth the primary tool for a seven-month-old? To explain this, Herman introduces the concept of the "sensory homunculus." This is a neurological map of the human brain’s sensory cortex where body parts are sized according to the amount of brain power dedicated to processing touch from that area. On this map, the hands are large, but the mouth and tongue are gargantuan.

Because the mouth has a higher density of sensory nerve endings than almost anywhere else on the body, it serves as a baby’s "high-definition scanner." While a seven-month-old’s fine motor skills in their hands are still developing, their mouth is already capable of detecting minute differences in texture, temperature, density, and shape. When a baby puts a wooden block or a plastic toy in their mouth, they aren't necessarily trying to eat it; they are gathering data. They are asking: Is this cold? Is it squishy? Does it have sharp edges? This oral exploration is a foundational milestone that builds the brain's initial database of the physical world.

Proprioception and the "Grandfather Face"

The discussion also touches on specific, often humorous, behaviors that parents notice. One such behavior is when a baby pulls their lips inward, mimicking a "grandfather without dentures." Herman explains that this is rarely a random quirk. At seven months, babies are often experiencing the movement of teeth beneath the gums. Pulling the lips in and rubbing them against the gums provides "proprioceptive feedback"—a sense of where their body parts are in space.

This self-massage serves a dual purpose: it soothes the pressure of incoming teeth and helps the baby map the limits of their own anatomy. It is a form of self-regulation and discovery. By testing these muscles, the baby is learning how to control the very tools they will eventually use for chewing solid foods and, eventually, speech.

Testing the Physics of Reality

Another milestone discussed is the "table drumming" phase. When a baby repeatedly smacks a surface, they are engaging in a multi-sensory feedback loop. They feel the vibration in their palm, hear the sound of the impact, and see the movement of their arm. Herman and Corn describe this as the baby "testing the physics of the world."

This behavior marks a shift from the baby being a passive recipient of sensations to an active seeker of them. For a "sensory seeker," these vibrations are incredibly satisfying and help the child feel grounded in their own body. It is the beginning of understanding cause and effect: If I hit this object with force, it creates a louder sound and a stronger vibration.

Sensory Profiles and Neurodiversity

A poignant part of the conversation focuses on the connection between these early milestones and later sensory profiles. Corn and Herman discuss how all babies appear to be sensory seekers because of their rapid brain growth, but early temperaments can sometimes hint at a child’s future sensory threshold.

Some children may grow up to be "sensory avoiders," easily overwhelmed by bright lights or loud noises, while others remain "sensory seekers" who require more intense input—like crunchy foods or constant movement—to feel regulated. Herman emphasizes that for parents who are neurodivergent or have unique sensory needs themselves, watching a baby hit these milestones offers a unique opportunity. Instead of viewing "mouthing" or "tapping" as behaviors to be stopped, these parents can recognize them as needs to be met.

Practical Applications: The Sensory Buffet

The episode concludes with practical advice for parents navigating this "determined scientist" phase. Rather than simply baby-proofing to prevent exploration, Herman suggests leaning into it through safe "sensory buffets." This includes providing a variety of textures—different fabric scraps, safe wooden teethers, or objects of varying temperatures.

They also introduce the concept of "heavy work" for babies. In occupational therapy, heavy work involves activities that push or pull against muscles and joints, providing deep pressure input that organizes the brain. For a seven-month-old, this might look like tummy time on a shaggy rug versus a smooth floor, or pushing a slightly weighted box.

Ultimately, Herman and Corn frame this stage of life as the construction of an internal "graph" of reality. Every object mouthed and every table drummed is a new node in the baby's mental map, connecting sensations to meanings. By understanding the "why" behind the chaos, parents can turn the frantic energy of the seven-month mark into a collaborative journey of discovery.

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Episode #644: The Mouth as a Scanner: Decoding Baby Sensory Milestones

Corn
You know Herman, there is something truly brave about being a parent. I was just watching Daniel with Ezra in the kitchen earlier, and it is like living with a tiny, incredibly determined scientist who has absolutely no concept of health and safety protocols.
Herman
Herman Poppleberry here, and you are absolutely right. Daniel’s prompt today really captures that frantic but fascinating energy of the seven-month mark. It is a wild time. Ezra is currently at that stage where the entire world is essentially one giant buffet, and his only method of peer review is his own mouth.
Corn
It is funny because Daniel mentioned that he started out baby-proofing for things like sharp corners on the coffee table, but then realized the real front line of defense is actually preventing his son from eating the monitor stand or a handful of baby wipes. It is a shift from protecting the baby’s body to protecting the baby’s digestive tract.
Herman
Exactly. And Daniel’s question is so poignant because he is looking at this through the lens of his own sensory experiences. He mentioned that he perceives the sensory world a bit differently, and seeing Ezra dive headfirst into these sensory milestones is making him wonder about the deeper mechanics. Why the mouth? Why now? And what does this tell us about how we all eventually learn to navigate the world?
Corn
I think we should start there. We talk about motor milestones all the time, like when a baby rolls over or sits up or starts to crawl. Those are the big, visible markers. But sensory milestones are the invisible architecture of development. They are happening in the background, but they are just as critical.
Herman
They really are. If you think about it, a baby is born into a literal explosion of data. Their eyes are learning to focus, their ears are being bombarded with sounds that do not have meaning yet, and their skin is constantly being touched by clothes, blankets, and hands. A sensory milestone is essentially a point where the brain learns how to organize that data into something useful. It is the difference between hearing a noise and recognizing a voice.
Corn
Right, it is the transition from just feeling things to actually perceiving them. So, let us tackle the big one Daniel brought up. The mouth. Why is a seven-month-old like Ezra so obsessed with putting everything in his mouth? I mean, he mentioned Ezra tried to stuff eight baby wipes in there the second he turned his back.
Herman
It sounds chaotic, but from a neurological perspective, it is incredibly efficient. To understand why, we have to talk about the sensory homunculus.
Corn
Oh, I love the homunculus. It is such a weird visual. For those who have not seen it, it is basically a map of the human brain’s sensory cortex, but it is drawn as a person where the body parts are sized according to how much brain power is dedicated to processing touch from that area.
Herman
Exactly. And if you look at a homunculus, the hands are huge, but the mouth and the tongue are absolutely massive. They are giant. This is because the mouth is one of the most sensitive parts of the human body. It has a higher density of sensory nerve endings than almost anywhere else. For a baby, their hands are still learning fine motor skills. They can grab things, sure, but they cannot really feel the nuances of texture, temperature, or density very well with their fingers yet.
Corn
So the mouth is like their high-definition scanner.
Herman
Precisely. When Ezra puts a monitor stand or a wooden block in his mouth, he is not just tasting it. He is using his tongue and lips to determine the exact shape, the temperature, the texture, and the hardness. Is it cold? Is it squishy? Does it have sharp edges? His brain is getting a massive influx of data that his hands simply are not capable of providing yet. This is called oral exploration, and it is a foundational sensory milestone.
Corn
It is interesting because we often think of the mouth as being for eating and speaking, but at seven months, its primary job is information gathering. I wonder if there is an evolutionary component to this too? I mean, it seems risky to put random things in your mouth, but we have been doing it for hundreds of thousands of years.
Herman
There is definitely a survival aspect. Before we had labels and plastic packaging, humans had to figure out what was edible and what was not. The mouth is the final gatekeeper. By exploring non-food objects with their mouths, babies are actually training their systems to recognize what belongs there and what does not. It is also linked to the development of the jaw and tongue muscles that will eventually be used for chewing solid food and, later, for speech.
Corn
That is a great point. It is not just about the brain; it is about the physical mechanics. But what about that specific behavior Daniel mentioned? The grandfather without dentures look. He said Ezra pulls his lips in and makes this funny face. Daniel asked a large language model about it, and it said it was normal, but I am curious what is actually happening there.
Herman
That is actually a classic seven-month behavior. It is often related to a couple of things. First, that is right around the time when the first teeth are usually starting to move under the gums. Even if they have not erupted yet, there is a lot of pressure and new sensation in the mouth. Pulling the lips in or rubbing the gums together is a way for the baby to provide their own sensory input to soothe that pressure. It is essentially self-massage.
Corn
Like a form of proprioceptive feedback?
Herman
Exactly. Proprioception is our sense of where our body parts are in space. By pulling his lips in and pressing them against his gums, Ezra is learning where his mouth ends and the rest of his face begins. He is testing the limits of his own anatomy. He is also probably discovering that he can control those muscles in a new way. It is like a kid discovering they can wiggle their ears, but for a baby, it is their whole world.
Corn
Daniel also mentioned Ezra has started tapping on things. Like, as he eats, he will smack the table back and forth. That seems like another one of those sensory-seeking behaviors.
Herman
Oh, the table drumming is a huge milestone. That is usually a sign that the baby is starting to understand cause and effect through a sensory loop. I hit the table, I feel the vibration in my hand, and I hear the sound. It is a multi-sensory experience. At seven months, they are moving from being passive observers to active participants in their environment.
Corn
It is like they are testing the physics of the world. If I hit this hard, does it sound different than if I hit it soft?
Herman
Exactly. And for a baby like Ezra, who might be a bit of a sensory seeker, that vibration is probably really satisfying. It provides what we call vestibular and proprioceptive input. It helps them feel grounded in their own bodies.
Corn
I want to go back to what Daniel said about his own sensory processing. He mentioned he experiences the world differently and he is watching Ezra’s development through that lens. It raises an interesting question about the connection between these early milestones and later sensory profiles. If a baby is a huge sensory seeker at seven months, does that mean they will be a sensory seeker as an adult?
Herman
That is a complex area of study, but there is definitely a connection. We all have a sensory threshold. Some people are sensory avoiders, meaning they get overwhelmed by loud noises or bright lights very easily. Others are sensory seekers, meaning they need more input to feel regulated. They might like crunchy foods, loud music, or constant movement.
Corn
Right, and we have talked about this in the context of neurodiversity before. Like in episode four hundred and twelve when we discussed sensory processing in adults.
Herman
Exactly. At seven months, almost all babies appear to be sensory seekers because they are in a period of rapid brain growth where they need that data. However, you can sometimes see the early outlines of a child’s temperament. If a baby is particularly intense about seeking out certain textures or vibrations, it might suggest they have a higher threshold for sensory input. But it is important to remember that at this age, it is all very fluid. The brain is incredibly plastic.
Corn
So, as a parent, how do you distinguish between a normal developmental milestone and something that might be a sensory processing issue? Because I know a lot of parents get anxious when they see their kids doing repetitive things like tapping or mouthing.
Herman
The key is usually functionality and distress. In a seven-month-old, mouthing and tapping are perfectly functional. They are learning. It becomes a concern only if the child seems stuck in those behaviors to the point where they cannot engage with people or other toys, or if they seem constantly distressed by normal sensory input, like the sound of a vacuum cleaner or the feel of certain fabrics.
Corn
That makes sense. It is about the balance. For Ezra, it sounds like he is just having a blast exploring. But for Daniel, who is mindful of his own sensory needs, it is actually a great advantage. He can recognize those needs in his son early on.
Herman
Absolutely. A parent who understands sensory processing can create a much more supportive environment. Instead of just saying, stop putting that in your mouth, they can provide safe, interesting things for the baby to mouth. They can recognize when the baby is getting overstimulated and needs a break. It turns parenting into a collaborative effort to regulate the child’s nervous system.
Corn
Let us talk about the practical side of that. If you have a seven-month-old who is in this intense oral and tactile exploration phase, what are some ways to lean into it safely? Because as Daniel said, you cannot just let them eat the monitor stand.
Herman
Right, the goal is to provide a sensory buffet that does not involve heavy metals or choking hazards. One of the best things is variety in texture. Most baby toys are smooth plastic or silicone, which is fine, but it is one note. Giving a baby different fabrics to feel, or safe wooden teethers with different grains, or even cold versus room temperature objects can be really stimulating.
Corn
I have seen people use those mesh feeders where you put frozen fruit inside. That seems like a triple threat of sensory input. You get the cold, you get the taste, and you get the texture of the mesh.
Herman
Those are fantastic. It provides intense sensory feedback that can be very calming for a baby who is seeking input. Another thing is what we call heavy work for babies.
Corn
Heavy work? That sounds like you are putting them to work in a coal mine.
Herman
Not quite. In occupational therapy, heavy work refers to activities that push or pull against the muscles and joints. For a seven-month-old, this could be something as simple as tummy time on different surfaces, like a shaggy rug versus a smooth floor. Or letting them push a weighted box across the floor once they are crawling. It provides that deep pressure input that helps organize the brain and improves body awareness.
Corn
It is fascinating how much of this is about organization. I think about Daniel’s mention of the graph on our website, myweirdprompts.com. He is trying to map the connections between all these different topics we discuss, and in a way, that is exactly what Ezra is doing with his brain. He is building his own internal graph of the world.
Herman
That is a perfect analogy. Every time Ezra puts something in his mouth, he is creating a new node in his mental map. This is hard, this is soft, this is cold. And then he starts to connect those nodes. This hard thing also makes a loud noise when I drop it. This soft thing tastes like nothing. He is building a database of reality.
Corn
And the mouth is the primary input device for that database right now. It is interesting to think about the transition. When does this phase typically end? When do kids stop leading with their mouths?
Herman
It usually starts to taper off between eighteen months and two years. By that point, their fine motor skills in their hands have caught up. They can use their fingers to explore the nuances of an object, so they do not need to use their tongues as much. Their vision has also become much more sophisticated. They can look at something and understand its texture without having to taste it.
Corn
So it is really a bridge. The mouth is a bridge to the hands and eyes.
Herman
Precisely. But even as adults, we never quite lose that oral sensory connection. Think about why people chew on pens when they are concentrating, or why we find certain food textures so comforting or repulsive. That early mapping that Ezra is doing right now in Jerusalem is setting the stage for his entire life’s relationship with the physical world.
Corn
It makes me wonder about the second-order effects of this. If a baby is restricted in their sensory exploration, like if they are always in a container or if they are never allowed to touch anything messy, does that impact their development later on?
Herman
There is a lot of evidence that it does. We see it sometimes in children who have sensory defensiveness or very picky eating habits. Often, there is a lack of varied sensory exposure in those early windows. If a baby does not get to experience different textures in their mouth at seven or eight months, they might find the transition to textured solid foods much more difficult later on. Their brain might interpret a new texture as a threat rather than just another piece of data.
Corn
That is a really important point for parents. The mess is actually part of the learning. When Ezra gets food all over his face and hands, or when he is gnawing on a wet washcloth, he is preventing future sensory issues.
Herman
Exactly. It is about building a robust sensory library. The more volumes you have in that library, the less likely you are to be startled or overwhelmed by a new experience later.
Corn
Let us talk a bit more about the lip pulling thing, the grandfather look. Daniel seemed particularly intrigued by that. Is there any connection between that and the development of sound production? Because seven months is also a big time for babbling, right?
Herman
Oh, absolutely. Around seven months, babies start doing what we call reduplicated babbling. That is the ba-ba-ba or da-da-da sounds. To make those sounds, you need a lot of control over your lips and tongue. That grandfather face is essentially Ezra practicing his lip closure. He is strengthening the muscles he needs to make those b and m sounds.
Corn
So he is not just making a funny face, he is in vocal spring training.
Herman
He really is. Every time he pulls his lips in or smacks them together, he is learning how to shape the air coming out of his lungs. It is all connected. The sensory input from his gums tells him where his lips are, and then he uses that information to try and mimic the sounds he hears Daniel and the others making in the house.
Corn
It is amazing how integrated it all is. You cannot separate the sensory from the motor or the cognitive. It is all one big, messy, beautiful process.
Herman
It really is. And I think it is important to acknowledge that this stage can be exhausting for parents. Daniel mentioned being constantly on guard. That is a real thing. It is called hypervigilance, and it is a natural response when your child is a fearless explorer.
Corn
Yeah, the word fearless stuck out to me in Daniel’s prompt. He said they are fearless at this age. And it is true. They do not have the life experience to know that a monitor stand might fall on them or that a baby wipe is not a snack.
Herman
And that is where the parent comes in as the external prefrontal cortex. The baby provides the curiosity and the drive to explore, and the parent provides the safety boundaries. It is a partnership. But if you can view that exploration as a critical developmental milestone rather than just a nuisance, it changes the energy of the interaction.
Corn
It turns a chore into a scientific observation.
Herman
Exactly. Instead of oh no, he is doing it again, it is oh look, he is exploring the density of that plastic. It does not make it less messy, but it makes it more meaningful.
Corn
I am curious about the tapping again. Daniel mentioned Ezra taps as he eats. Is there a rhythmic component to sensory milestones?
Herman
Definitely. Rhythm is one of the first ways babies learn to organize time and movement. The vestibular system, which is located in the inner ear and handles balance and spatial orientation, is very closely linked to our sense of rhythm. Tapping in a rhythmic way helps a baby feel a sense of predictability. It is a way of saying, I do this, and then this happens. It is very grounding.
Corn
It is like they are creating their own heartbeat for the environment.
Herman
That is a lovely way to put it. And for a baby who might be feeling a bit overwhelmed by the sensory input of a meal—the different tastes and textures—that rhythmic tapping might be a way for them to stay regulated. It is a self-soothing mechanism.
Corn
So, we have covered the mouth as a high-definition scanner, the homunculus, the lip pulling as muscle training, and the tapping as a rhythmic grounding exercise. What is next for a seven-month-old? What is the next big sensory milestone Daniel should be looking out for?
Herman
The next big shift is usually around nine to ten months, and that is when they start to develop the pincer grasp. This is when they can pick up small things with their thumb and forefinger. This changes their sensory world again because suddenly they can explore tiny details. This is also when they start to develop a better sense of depth perception and spatial awareness.
Corn
So the exploration gets more refined.
Herman
Exactly. They move from the sledgehammer approach of putting the whole object in their mouth to a more surgical approach of feeling a tiny crumb or a piece of lint. And of course, that just means the parent has to be even more careful about what is on the floor.
Corn
It never ends, does it?
Herman
Not for a while. But that is the joy of it. You are watching a human mind boot up in real time.
Corn
It really makes me appreciate the complexity of the human experience. We take it for granted that we can walk into a room and understand what everything is, but we all had to go through this phase. We all had to taste the world to understand it.
Herman
We did. And I think that is a great takeaway for anyone listening, whether you are a parent or not. We all have these sensory needs. We all have different thresholds. Understanding these early milestones helps us be more compassionate toward ourselves and others. We are all just trying to navigate a very loud, very bright, very textured world.
Corn
Well said, Herman. I think we have given Daniel a lot to think about next time he is fishing a baby wipe out of Ezra’s mouth. It is not just a wipe; it is a data point.
Herman
Exactly. And Ezra is doing a great job. He is exactly where he needs to be.
Corn
Before we wrap up, I want to say that if you are enjoying these deep dives into the weird and wonderful ways our brains develop, we would really appreciate it if you could leave us a review on your favorite podcast app. It really helps other curious people find the show.
Herman
It truly does. We love seeing the community grow, especially when we get to tackle such personal and fascinating prompts like this one from Daniel.
Corn
And if you want to see that graph Daniel was talking about, or if you want to send us your own weird prompt, head over to myweirdprompts.com. You can find all our past episodes there, and there is a contact form if you want to get in touch.
Herman
We are also on Spotify, so you can follow us there to make sure you never miss an episode.
Corn
This has been My Weird Prompts. I am Corn.
Herman
And I am Herman Poppleberry.
Corn
Thanks for listening, and we will talk to you next time.
Herman
Goodbye everyone.

This episode was generated with AI assistance. Hosts Herman and Corn are AI personalities.

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