Chapter 3 – Sensory Development

Just like the neural connections that control innate reflexes, the senses are already formed when the baby is born. Some are already sharply active, while others still need to mature, adjusting to the stimuli of the external environment.

The first sense the fetus develops in the womb is the sense of touch. This is demonstrated by ultrasound images: the baby plays with its hands, feet, and umbilical cord and responds to the mother’s touch on her abdomen (5).

From the very first days of life, the baby explores objects through touch and creates a mental representation of them, to the point that they recognize as familiar those they have already examined (6).

But the sense of touch for a baby is much more than a tool for understanding their surroundings: it is closely connected with the brain centers from which emotions and ancestral mechanisms of social behavior originate. A newborn who frequently experiences skin-to-skin contact with the mother, who is caressed and hugged, feels safe and relaxes their defense mechanisms. Their cortisol levels—the stress hormone—are lower, while serotonin levels, which promote well-being, are higher.

Hearing

Unlike vision, hearing is already developed and functioning during pregnancy. The fetus can perceive some external sounds (8), including the mother’s and father’s voices, which they learn to recognize. After birth, hearing those familiar voices has a calming effect.

In the first few weeks of life, the baby cannot yet distinguish words from background noise (9). Speaking to them in “baby talk”—with elongated vowels and higher-pitched tones—helps them focus on words and stimulates the development of auditory areas in the brain, which will soon enable them to speak in return.

By around 2 months the baby’s hearing has developed enough to begin distinguishing different tones. By 3–4 months, the baby can locate the source of a voice or sound and turn toward it. They also begin to vocalize consonants and vowels. Around 5–6 months, they start to understand that some sounds are caused by their own actions—such as dropping objects to hear the noise they make, which often delights them and provokes loud laughter.

To assess whether a baby has healthy hearing, simple stimuli can be used—for example, lightly clapping hands in one direction to get their attention. If the baby turns toward the sound, there are likely no issues. If they don’t respond to any stimuli, it could indicate a hearing problem.

In that case, it is advisable to consult the pediatrician to diagnose and address the issue promptly.

Taste and Smell

These two senses develop in parallel during pregnancy and are already highly acute at birth.

Smell is closely connected not only to taste but also to emotions, making it crucial to the baby’s psychomotor development, beginning with the bonding process with the mother in the early days of life.

At birth, the newborn’s well-developed sense of smell allows them to recognize their mother even before they can see her, guiding them toward the breast.

After the first contact with the mother, the baby also learns to recognize the smell of her milk, which studies show they prefer over formula or the milk of other women (10). They can even distinguish caregivers by their scent. The intimate connection between smell and emotion also explains how this sense strongly influences memory. Scents associated with early experiences will remain closely tied to those emotions, to the point where a familiar smell can trigger emotional reactions even years later.

Regarding taste, the baby experiences the flavors of the foods the mother eats through the amniotic fluid during pregnancy. Being exposed to a healthy, varied diet from the womb will later make the baby more open to accepting those same flavors during weaning.

By nature, in the first months of life, babies particularly enjoy sweet and umami (savory) flavors, such as the taste of glutamate—a component of breast milk. They show expressions of disgust when tasting bitter or sour flavors and are indifferent to salty ones. These instinctive preferences are evolutionarily driven, designed to steer babies away from potentially toxic plants and substances and toward energy-dense foods.

In today’s society, where calorie-dense sweet foods are abundant and the biggest risk is often overweight rather than undernourishment, these preferences can be problematic for parents. Moms and dads will need to work patiently and consistently to educate their children to follow a healthy and varied diet, rich in vegetables and fiber. Over time, with exposure and example, children will overcome their natural resistance to new flavors and become more willing to try a wider range of foods. (11).

Vision

Vision plays a fundamental role in a child’s physical, psychological, and emotional development from birth, although full visual maturity is only reached around eight months of age.

The eyes, optic nerve, and visual cortex—the brain region responsible for receiving and decoding visual signals—begin developing early in pregnancy and are ready to function at birth. However, they need external stimulation to become active and fully mature (12).

A newborn’s vision is blurred, as if surrounded by a thick fog. They can perceive light and dark and some large shapes at close range, such as the mother’s face, but not distant objects or fine details. Their color perception is limited, and their eyes sometimes move in an uncoordinated way, which can resemble strabismus. This is a normal and temporary phenomenon, as their eye muscles are not yet fully controlled.

At 15 days old the baby starts distinguishing shapes more clearly up to 20–30 centimeters away (13). Around one month, eye movements become more coordinated, allowing the baby to focus and roughly track moving objects. By two months, they show a preference for bright colors and high-contrast images (e.g., black and white or light vs. dark tones), and color differentiation begins to sharpen. Over the following months, they become increasingly able to distinguish object details and images. At 3–4 months, the baby develops the fixation reflex, the ability to focus on and follow an object that draws their attention—and begins recognizing facial features and expressions, soon imitating them. They increasingly coordinate their eye movements and follow moving objects with greater accuracy. From four months onward, better control of movement is paired with growing depth perception.

Around 5 months the baby’s visual horizon expands, and they begin to focus on more distant objects. The ability to distinguish colors also becomes fully developed at this stage. Three-dimensional vision, depth perception—develops later, around the first year of life, as the child begins to walk. By twelve months, their visual ability matches their increasing motor skills: walking and moving independently helps refine their spatial awareness. By age 2 they have full control of their eye muscles and by age 4, their visual acuity is comparable to that of an adult.