The human body is an intricate system, constantly interacting with the world through its senses. These abilities allow us to perceive and interpret our surroundings. Understanding how these senses develop, particularly which one emerges first, offers insights into the earliest stages of human formation, beginning long before birth.
The Primacy of Touch
Among human senses, touch is the first to develop. This fundamental sensory modality is present remarkably early in gestation, laying the groundwork for subsequent sensory and cognitive development.
Early Development of Touch
Touch development begins around eight weeks of gestation. Specialized touch receptors first appear in the perioral region, including the lips and nose. Over subsequent weeks, this sensitivity gradually extends across the body. By approximately 12 weeks, the palms and soles become responsive, followed by the abdomen around 17 weeks. By the mid-third trimester (around 32 weeks), the entire body is sensitive to touch, even a light brush.
As touch sensitivity progresses, fetuses exhibit reflexive reactions to tactile stimulation. Early movements include contracting neck muscles when the perioral region is stroked, causing the touched area to move away. Later, fetuses may actively seek touch, for instance, by touching their own eyelids, feet, or grasping the umbilical cord. This increasing self-touch behavior, especially in the third trimester, suggests a growing exploration of their bodies and environment.
The Role of Touch in Early Life
Touch plays a significant role in both prenatal and postnatal development. Within the womb, the fetus uses touch to explore its confined environment, interacting with the uterine wall, umbilical cord, and even other fetuses in multiples. This early tactile exploration contributes to the formation of early attachments and initial learning about the world.
After birth, touch remains highly important for newborns and infants. It is a primary means of communication and a powerful tool for bonding between caregiver and infant. Skin-to-skin contact, for example, helps regulate a baby’s temperature, heart rate, and breathing, promoting relaxation and fostering attachment. Touch also supports cognitive development, sensory integration, and provides comfort. Adequate tactile stimulation positively influences growth and development, while a lack of nurturing physical contact can have negative consequences.
Sequential Development of Other Senses
While touch leads, other senses develop sequentially throughout gestation. Taste buds begin to form around eight weeks, and by 13 to 15 weeks, the fetus has taste buds similar to an adult’s, experiencing flavors from the amniotic fluid. Smell also emerges around this time, with olfactory nerves connecting to the brain by 13 weeks and the fetus capable of smelling and responding to odors in amniotic fluid by 28 weeks.
Hearing development progresses with ear structures forming between 23 and 25 weeks, and the fetus responding to sounds as early as 16 weeks, showing responses to loud noises by 23 weeks. The auditory system becomes functional around the seventh month of pregnancy, though parts of the inner ear may perform functions earlier. Sight is generally the last major sense to fully mature. Although eyelids develop and light penetration can occur as early as 22 weeks, and optic nerve myelination begins around 23-25 weeks, clear vision continues to develop significantly after birth. Newborns are initially very short-sighted and primarily see in shades of gray, with full visual acuity developing over the first several months and years of life.