7.4: Sensory Capacities

Throughout much of history, the newborn was considered a passive, disorganized being who possessed minimal abilities. William James, an early psychologist, had described the newborn’s world as “a blooming, buzzing confusion,” (Shaffer, 1985). However, current research techniques have demonstrated just how developed the newborn is with specially organized sensory and perceptual abilities.

Vision

Figure \(\PageIndex{1}\): A newborn gazing up at a parent.[1]

Figure \(\PageIndex{2}\): An adult carefully holding an infant. (Photo Source: Pikrepo, DMCA)

The womb is a dark environment void of visual stimulation. Consequently, vision is the most poorly developed sense at birth and time is needed to build those neural pathways between the eye and the brain. Newborns' visual acuity is about 20/400, which means that an infant can see something at 20 feet that an adult with normal vision could see at 400 feet. Thus, the world probably looks blurry to young infants. Because of their poor visual acuity, they look longer at checkerboards with fewer large squares than with many small squares. Infants' thresholds for seeing a visual pattern are higher than adults'. Thus, toys for infants are sometimes manufactured with black and white patterns rather than pastel colors because the higher contrast between black and white makes the pattern more visible to the immature visual system. By about 6 months, infants' visual acuity improves and approximates adult 20/25 acuity.

Figure \(\PageIndex{3}\): An infant looking up at the person feeding them.[2]

When viewing a person’s face, newborns do not look at the eyes the way adults do; rather, they tend to look at the chin—a less detailed part of the face. However, by 2 or 3 months, they will seek more detail when exploring an object visually and begin showing preferences for unusual images over familiar ones, for patterns over solids, for faces over patterns, and for three-dimensional objects over flat images. Newborns have difficulty distinguishing between colors, but within a few months they are able to discriminate between colors as well as adults do. Sensitivity to binocular depth cues, which require inputs from both eyes, is evident by about 3 months and continues to develop during the first 6 months. By 6 months, the infant can perceive depth in pictures as well (Sen, Yonas, & Knill, 2001). Infants who have experience crawling and exploring will pay greater attention to visual cues of depth and modify their actions accordingly (Berk, 2007).

Hearing

The infant’s sense of hearing is very keen at birth, and the ability to hear is evidenced as soon as the 7th month of prenatal development (DeCasper and Spence, 1986). In fact, an infant can distinguish between very similar sounds as early as one month after birth and can distinguish between a familiar and unfamiliar voice even earlier. Infants are especially sensitive to the frequencies of sounds in human speech and prefer the exaggeration of infant-directed speech (discussed in more detail in the section on language). Newborns also prefer their mother’s voices over another female when speaking the same material (DeCasper & Fifer, 1980). Additionally, they will register in utero specific information heard from their mother’s voice.[3]

Prenatal development

DeCasper and Spence (1986) tested 16 infants whose mothers had previously read to them prenatally. The mothers read several passages to their fetuses, including the first 28 paragraphs of The Cat in the Hat, beginning when they were 7 months pregnant. The fetuses had been exposed to the stories on average of 67 times or 3.5 hours.

Figure \(\PageIndex{4}\): When pregnant mothers read “Cat in the Hat” to their bellies at 7 months, infants responded differently to the sound of their mothers reading the same book than any other book after birth.[5]

Ullal et al (2013) reviewed multiple research studies and suggested that "even prior to birth" - as early as 25 weeks in utero - "human listeners may begin to acquire rudimentary auditory representations that may be considered as the earliest building blocks" of language and music.

Touch and Pain

Immediately after birth, a newborn is sensitive to touch and temperature, and is also highly sensitive to pain, responding with crying and cardiovascular responses (Balaban & Reisenauer, 2013). Newborns who are circumcised, which is the surgical removal of the foreskin of the penis, without anesthesia experience pain as demonstrated by increased blood pressure, increased heart rate, decreased oxygen in the blood, and a surge of stress hormones (United States National Library of Medicine, 2016). Research has demonstrated that infants who were circumcised without anesthesia experienced more pain and fear during routine childhood vaccines. Fortunately, many circumcisions are now done with the use of local anesthetics.

Taste and Smell

Studies of taste and smell demonstrate that babies respond with different facial expressions, suggesting that certain preferences are innate. Newborns can distinguish between sour, bitter, sweet, and salty flavors and show a preference for sweet flavors. Newborns also prefer the smell of their mothers. An infant only 6 days old is significantly more likely to turn toward its own mother’s breast pad than to the breast pad of another baby’s mother (Porter, Makin, Davis, & Christensen, 1992).

Figure \(\PageIndex{5}\): Young infants are soothed sucking on a pacifier.[7]

Interaction between different senses

Infants seem to be born with the ability to perceive the world in an intermodal way; that is, through stimulation from more than one sensory modality. For example, infants who sucked on a pacifier with a smooth surface preferred looking at visual models of a pacifier with a smooth surface. But those that were given a pacifier with a textured surface preferred to look at a visual model of a pacifier with a textured surface.[6]

Ullal et al (2013) review of prenatal audition also showed that infants look more at the faces of adults who speak their native language (especially those who speak without an accent and with the same cadence) than at faces of adults who speak a different language (or those who speak with an accent).

By 4 months, infants can match lip movements with speech sounds and can match other audiovisual events. Although sensory development emphasizes the afferent processes used to take in information from the environment, these sensory processes can be affected by the infant's developing motor abilities. Reaching, crawling, and other actions allow the infant to see, touch, and organize his or her experiences in new ways.[8].

Figure \(\PageIndex{6}\): The responses of infants to different tastes – sweet, sour and bitter.[9]

References:

Ullal, S., Vanden Bosch der Nederlanden, C., Tichko, P., Lahav, A., & Hannon, E. (2013). Linking prenatal experience to the emerging musical mind. Frontiers in Systems Neuroscience, 7. doi: 10.3389/fnsys.2013.00048 (licensed CC-BY)

Attributions:

Child Growth and Development by Jennifer Paris, Antoinette Ricardo, and Dawn Rymond, 2019, is licensed under CC BY 4.0

[1] Image is in the public domain

[2] Image by Ben_Kerckx on Pixabay

[3] Lifespan Development: A Psychological Perspective (pages 76-77) by Martha Lally and Suzanne Valentine-French is licensed under CC BY-NC-SA 3.0

[4] Lifespan Development: A Psychological Perspective (page 76) by Martha Lally and Suzanne Valentine-French is licensed under CC BY-NC-SA 3.0

[5] Image by kamiel79 on pixabay

[6] Lifespan Development: A Psychological Perspective (pages 76-77) by Martha Lally and Suzanne Valentine-French is licensed under CC BY-NC-SA 3.0

[7] Image by Beeki is licensed under CC0 1.0

[8] Lifespan Development: A Psychological Perspective by Martha Lally and Suzanne Valentine-French is licensed under CC BY-NC-SA 3.0

[9] Image by Alice Vilela and Fernanda Cosme is licensed under CC BY 4.0

Parenting and Family Diversity Issues by Diana Lang, 2020, published by Iowa State University is licensed under CC BY-NC-SA 4.0