【Children's Perspective Lab】We tried crying like a baby using Baby Voice.

"Why won't they stop crying?" Not understanding a baby's feelings

You've fed them, changed their diaper, and held them, but the baby just won't stop crying. You've tried rocking them gently and taking them for a walk, but nothing works. As a parent, you feel completely lost trying to understand your baby's feelings, and you feel like you might cry yourself. Many new moms and dads have probably experienced this feeling, right? I've actually cried "Waaah!" more than once or twice myself.

But as my child grew and could communicate with words, it suddenly hit me. For a baby who can't speak yet, crying is their only way to communicate. How must it feel to have no other way to say you're uncomfortable, thirsty, or your feet itch? The "Child's Perspective Lab," which conducts activities to deepen understanding of children by having adults experience childhood, decided to create a device called "Baby Voice" to experience a baby's feelings firsthand. This device converts all spoken words into crying sounds.

First, creative technologist Ryunosuke Ono built the internal device. He attached a small microphone to a single-board computer about the size of a business card, equipped with an entry-level PC CPU. He programmed it to detect the volume of the user's voice. When it exceeds a certain level, a baby's cry sounds from the speaker.

We took this to Space Art Studio, set it into a mold of a baby's mouth, and adjusted the speaker position and the volume of the baby's cry. Completion was finally in sight.

Baby Voice Production Scene

However, as we progressed, a question arose: Does a baby's cry change depending on their emotions? If we could distinguish these cries, wouldn't parents understand what their baby wants and find it easier?

Therefore, Fumiko Ishida and Mitsuhiro Kutsukake from the Children's Perspective Lab decided to consult Professor Yoko Okamoto of Rissho University, who has researched parent-child communication for over 20 years.

Babies cry for reasons like "boredom" or "being bored"

Ishida: Professor, this is the Baby Voice we're currently developing.

Professor Okamoto (hereafter, Professor): What an incredibly interesting project! I'd love to try it. Please let me experience it once it's finished.

Ishida: Of course! By the way, Professor, we're currently debating whether we should change the crying sounds to match emotions. Can babies' voices actually be distinguished based on emotion? Personally, I couldn't tell my own child's cries apart at all.

Professor: Regarding baby cries, medical and speech analysis research has attempted to classify them, and we know there are phonetic characteristics in situations where the cause of crying is clearly different (※1). However, in reality, the background for crying—like being sleepy or hungry—isn't singular, and the intensity varies greatly. So, I think the current understanding is that "the differences aren't significant enough for people to reliably distinguish them."

※1
Reference: Arakawa, K. (2007). Quantitative analysis of infant cries and estimation of crying causes. Fundamentals Review, 1(2), 21-25.

Many parents I've encountered in surveys also say, "You can't tell just by the sound." Do you know what parents usually do first when their baby starts crying? They glance at the clock. "Is it feeding time? Oh, it's too early, so maybe it's a diaper." They make guesses like that.

Babies under three months old, especially, have immature throat structures, so their cries are weak, nasal sounds like air escaping through the nose. Their abdominal muscles are also underdeveloped, so they don't have much volume. I think it's developmentally difficult for them to clearly differentiate their cries. That's why our research (※2) focuses on distinguishing cries from around five or six months old, when they're a bit more developed.

※2
Yoko Okamoto & Yukie Sugano, 2008, Developmental Psychology of Parents and Children, Shinyosha

Kutsukake: I see. On another note, do the reasons for crying change with age?

Professor: Well, it could be said they change, but it could also be said they don't. They cry because they're hungry, sleepy, in pain, too hot... and also because they're "bored."

Kutsukake: Huh? They cry because they're bored?

Teacher: Yes. Humans are born with intellectual curiosity, so it seems they cry even when bored. Some researchers (※3) say "fake crying starts around 3 weeks old." They cry to get attention and call for someone. But studying babies is difficult—we can't ask them if that's really true.

※3
Reference: Wolff, P.H. (1969). The natural history of crying and other vocalizations in early infancy. In Foss, B. M. (Ed). Determinants of infant behavior Ⅳ. London; Methuen.

Ishida: That's certainly true...

Doctor: Something parents often overlook with their first child is whether the baby is too hot or cold. Babies have a higher body temperature, but adults, who have lower body temperatures and are better at regulating them, tend to worry and overdress them. When I visit families with their first child, it's actually not uncommon to see babies with bright red faces from being overdressed.

Ishida: I can relate. I was so anxious I dressed mine way too warmly, and only realized months later that I might have been overdressing them. But there's another thing I wish I'd known much sooner. The idea that babies go through a "crying peak" period where nothing seems to stop them from crying.

Teacher: It's true, there is a phase where nothing seems to work. We often hear parents say, "My baby slept so well since birth, but now the evening fussiness and twilight crying has started—why?" While we haven't collected data on this, it coincides with the time when baby care routines become established. Evening is also when adults get busy with other tasks—like "I need to prepare dinner" or "I haven't done this or that yet!"—so the baby might just want more attention. Also, babies grow much faster than adults realize. What was the perfect amount of milk yesterday might not be enough today.

Kutsukake: So, in the end, we just have to make various guesses and try different approaches, right?

Doctor: Exactly. But what I want to tell worried moms and dads first is that not knowing why they're crying is perfectly normal. Worrying when you don't know the reason is proof you're trying to understand. I think it's a sign of being a good parent who wants to understand their child.

Ishida: Hearing those warm words now... if I'd heard them during those nights of endless midnight cuddling, I probably would've burst into tears. Honestly, I'm still a little teary-eyed now.

Babies aren't born as "blank slates." They each have their own temperament!

Ishida: My son was the type who would cry the moment you put him down—what we call a "back switch" baby. But some babies are perfectly content when you lay them down. They're born with their own personalities, right?

Professor: That's right. Babies aren't born as blank slates; they have innate temperaments. Temperament refers to their individuality at birth, which then develops and interacts with environmental factors to shape their personality. There are various ways to categorize it, but a well-known classification identifies three types (※4).

※4
Reference: Thomas, A. & Chess, S. (1986). The New York longitudinal study: From infancy to early adult life. In Plomin, R. & Dunn, J. (Eds.) The study of temperament; Changes, continuities, and challenges. Lawrence Erlbaum Associates, Inc.

First is the easy baby—easy to handle, easy to care for, cries when hungry, and sleeps soundly after feeding. Second is the difficult baby—often called hard to handle or fussy, may fuss even after feeding, cries when put down, and is generally sensitive. The third is the slow-to-warm-up baby, often described as slow to get going or a laid-back child, who reacts slowly to stimuli. Of course, temperament is just that—personality changes based on upbringing and various experiences later in life.

Ishida: Just knowing these temperaments exists can make parents feel more at ease. I thought, if I'd known, I wouldn't have worried so much, thinking, "Is it my fault this baby cries all the time...?"

Teacher: If you're struggling with how to interact with your baby, I recommend "speaking for them" (※5).

※5
Okamoto, Y. (2016). Transition to Parenthood from Pregnancy to Infancy: The Development of Parents Through Parent-Child Interaction. Shinyosha.

Kutsukake: You mean speaking for the baby's feelings?

Teacher: Yes. For example, when Mom feeds the baby and says, "Are you full? Yes, you're full now," right? Even though the baby knows asking won't get an answer, they ask anyway. By playing both roles, Mom can draw a line and think, "Let's just leave it at that." This allows her to move on to the next action.

Kutsukake: I see. So it's about reassuring herself.

Teacher: Exactly. Actually, this is something many parents do naturally. It's perfectly normal to feel anxious when spending time with a baby who can't speak. Often, the time spent with a baby just feels empty. Singing songs is great too. It fills the time, doesn't it?

Ishida: That's true! I used to sing constantly while walking with my child in my arms. I realize now it was to fill the silence—for my own sake.

Teacher: Singing or speaking on their behalf eases the parent's mind. Even if it's just guessing (like, "Did you want to be held? Yeah, you wanted to be rocked, right?" or "You're sleepy, huh? Ah, sleepy, sleepy!"), speaking for them somehow helps you gradually get better at catching the baby's expressions and actions. It sharpens your observational skills toward the baby. That's how you start to grasp how to interact with that child.

Ishida: That's fascinating~. I feel like I'm starting to grasp some tips for communicating with babies. Thank you so much, Teacher!

We had new moms and dads try out "Baby Voice"

Since distinguishing a baby's voice based on emotion is difficult, we designed "Baby Voice" to randomly play baby cries in response to speech. So, here's the finished product. We decided to have moms and dads currently caring for babies try it out and film their reactions.

The Matsuura family kindly agreed to help. Their daughter, Itoha-chan, is 6 months old. Holding the actual Baby Voice device, the happy couple remarked, "It looks like a peach~". First, we had husband, Kōta-san, wear it while wife, Marika-san, spoke to him. Would the feelings come through?
 
"Waaah waaah waaah!! (It's hot! Get the AC remote!)"
"Hm? Want something to drink? Water? Water? No?"
"Waaah waaah waaah!! (No, get the AC remote!)"
"This? Is this what you want? No? Oh, maybe the bathroom?"
 
I took my husband to the bathroom, but it seems he didn't actually need to go. He couldn't communicate at all, and as his cries echoed through the house, time just passed. Next, I had his wife, Marika, put it on him.
 
"Waaah waaah!! (I want tea!)"
"Ah, got it. You want something to eat. You want to eat, right? Huh? No?"
"Waaah, waaah, waaah!! (No, that's not it, I want tea)"
 
They keep bringing me things like tissues and the TV remote, but it's not what I want. It's like they're thinking, "Why don't you understand?" I try all sorts of things, but none of them seem to be what I want.
 
"Tired? Sleep? Want to take a little nap?"
 
As time just keeps passing, nearing the end,
 
"Ah, tea! How about some tea?"

Mr. Kōdai poured tea into a cup and brought it over. The crying stopped. It got through!!! The filming set was enveloped in a kind of emotion. How incredibly difficult it is to communicate through crying.
 
"Experiencing it myself, I realized how little gets through. I thought, 'I really shouldn't get frustrated just because I don't know why they're crying.' It's about making the effort to understand," said Ms. Kōdai.

"Doing this myself made me realize it might not just be diapers, milk, or sleepiness—there could be so many other discomforts," said Marika. "I think I'll try to be more open to exploring different possibilities from now on." Though babies can only cry, this experience helped them truly grasp that babies have feelings they want to express.

Watch the experience videos of the three couples we interviewed—expectant parents and parents of one-year-olds—here

Here's what we learned and summarized from this study.

● It's normal not to know why a baby is crying. Beyond diaper discomfort, hunger, sleepiness, or being too hot/cold (overdressing), remember they might cry out of boredom.

● Babies are born with distinct "temperaments." Examples include Easy Babies, Difficult Babies, and Slow-to-Warm-Up Babies. Since many Difficult Babies are said to be challenging, don't overthink your caregiving approach.

● If you struggle to fill the time with your baby, try "Are you hungry? Hungry, hungry~" or "Tired? Sleepy, sleepy" – speak for your baby. Observing their reactions while playing both roles will gradually help you understand how to connect with them.

Wearing the "Baby Voice" device made me truly feel the frustration of having crying as the only way to communicate. Telling a baby "Don't cry" might be like telling an adult "Don't speak"? I felt it would be good to try not to think too much about "not letting them cry," but rather to understand they're trying so hard to tell us something.

Now, the experiential exhibition "Children's Vision Exhibition," which featured the baby voice we created, has successfully concluded. We received an overwhelmingly positive response, welcoming over 15,000 visitors. We've also received many requests asking, "Please hold it in other prefectures too." We welcome inquiries for touring exhibitions at municipal facilities, art museums, commercial spaces, corporate exhibition areas, and more. Please contact us via the Dentsu Inc. website or inquiry page below.

【"Children's Vision Exhibition" Overview】
Organizer: ITOCHU SDGs STUDIO
Cooperation: Children's Perspective Lab
Period: Now concluded
Venue: ITOCHU SDGs STUDIO (Itochu Garden B1F, 2-3-1 Kita-Aoyama, Minato-ku, Tokyo)
*For exhibition details, please visit the official website.