As you remember from Chapter 2, Jean Piaget was a Swiss scientist who earned his doctorate in 1918, when most scientists thought infants ate, cried, and slept but did not yet learn. When Piaget became a father, he used his scientific observation skills with his own babies. Contrary to conventional wisdom, he realized that infants are active learners, adapting to experience. His theories and observations have earned Piaget the admiration of developmentalists ever since. (Developmental Link: Piaget’s theory of cognitive development is introduced in Chapter 2.)

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Piaget called cognition in the first two years sensorimotor intelligence, named about the early senses and motor skills described in Chapters 4 and 5. Those early reflexes and body movements are used by infants to develop their minds, adapting to experience. Sensorimotor intelligence is subdivided into six stages (see Table 6.1).

In every aspect of sensorimotor intelligence, the brain and the senses interact with experiences, each shaping the other as part of a dynamic system (Ambady & Bharucha, 2009). Piaget described the interplay of sensation, perception, and cognition as circular reactions, emphasizing that, as in a circle, there is no beginning and no end. Each experience leads to the next, which loops back (see Figure 6.1). The first two stages of sensorimotor intelligence are primary circular reactions, involving the infant’s body.

Stage one, called the stage of reflexes, lasts only a month. It includes senses as well as motor reflexes, the foundations of sensorimotor thought. Soon reflexes become deliberate actions; sensation leads to perception, perception leads to cognition, and then cognition leads back to sensation.

Stage two, first acquired adaptations (also called stage of first habits), begins because reflexes adjust to whatever responses they elicit. Adaptation is cognitive; it includes both assimilation and accommodation. (Developmental Link: Assimilation and accommodation are explained in Chapter 2.) Infants adapt their reflexes as their responses teach them about what the body does and how each action feels.

Here is one example. In a powerful reflex, full-term newborns suck anything that touches their lips. Their first learning challenge is to suck, swallow, and suck again without spitting up too much—a major task that often takes a few days, with the mother learning how to help her baby latch, suck, and swallow.

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During the first stage, in the first month, infants adapt their sucking reflex to bottles or breasts, pacifiers or fingers, each requiring specific types of tongue pushing. This adaptation signifies that infants have begun to interpret sensations; as they accommodate, they are “thinking.”

During stage two, which Piaget pegged from about 1 to 4 months of age, additional adaptation of the sucking reflex begins. Infant cognition leads babies to suck in some ways for hunger, in other ways for comfort—and not to suck fuzzy blankets or hard plastic. Once adaptation occurs, it sticks.

Adaptation is quite specific. For instance, 4-month-old breast-fed babies may reject milk from the nipple of a bottle if they have never experienced it. Or suppose 4-month-olds have discovered how to suck their thumbs, and have practiced thumb-sucking to their joy and satisfaction. Then suppose the parents decide that a pacifier is better—cleaner, perhaps, or healthier for teeth. That may be too late. Their baby may refuse to readapt, spitting out the pacifier and finding the thumb instead. Piaget believed that people of all ages tend to be stuck in their ways for cognitive reasons; early adaptation is one example.

In stages three and four, development advances from primary to secondary circular reactions. Those reactions extend beyond the infant’s body; this circular reaction is between the baby and something else.

During stage three (4 to 8 months), infants attempt to produce exciting experiences, making interesting sights last. Realizing that rattles make noise, for example, they wave their arms and laugh whenever someone puts a rattle in their hand. The sight of something delightful—a favorite squeaky toy, a smiling parent—can trigger active efforts for interaction.

Next comes stage four (8 months to 1 year), new adaptation and anticipation (also called the means to the end). Babies may ask for help (fussing, pointing, gesturing) to accomplish what they want. Thinking is more innovative because adaptation is more complex. For instance, instead of always smiling at Grandpa, an infant might first assess his mood. Stage-three babies know how to continue an experience; stage-four babies initiate and anticipate.

An impressive attribute of stage four is that babies work hard to achieve their goals. A 10-month-old girl might crawl over to her mother, bringing a bar of soap as a signal to start her bath, and then start to remove her clothes to make her wishes crystal clear—finally squealing with delight when the bath water is turned on. Similarly, if a 10-month-old boy sees his father putting on his coat to leave, he might drag over his own jacket to signal that he wants to go along.

At that age, babies indicate that they are hungry—and keep their mouths firmly shut if the food on the spoon is something they do not like. If the caregivers have been using sign language, among the first signs learned by 10-month-olds are “eat” and “more.” Even without parental signing, babies this age begin displaying some universal signs—pointing, pushing, and reaching up to be held. These cognitive advances benefit from new motor skills (e.g., crawling, grabbing, hand gestures), which result from brain maturation—dynamic systems again.

With a combination of experience and brain maturation, babies become attuned to the goals of others, an ability much more evident at 10 months than 8 months (Brandone et al., 2014). It seems that at Piaget’s fourth stage of sensorimotor intelligence, personal understanding begins to extend to social understanding.

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Piaget thought that, at about 8 months, babies first understand the concept of object permanence—the realization that objects or people continue to exist when they are no longer in sight. As Piaget discovered, not until about 8 months do infants search for toys that have fallen from the crib, rolled under a couch, or disappeared under a blanket. Blind babies also acquire object permanence toward the end of their first year, reaching for an object that they hear nearby (Fazzi et al., 2011).

As a recent statement of this phenomenon explains:

Many parents in our typical American middle-class households have tried out Piaget’s experiment in situ: Take an adorable, drooling 7-month-old baby, show her a toy she loves to play with, then cover it with a piece of cloth right in front of her eyes. What do you observe next? The baby does not know what to do to get the toy! She looks around, oblivious to the object’s continuing existence under the cloth cover, and turns her attention to something else interesting in her environment. A few months later, the same baby will readily reach out and yank away the cloth cover to retrieve the highly desirable toy. This experiment has been done thousands of times and the phenomenon remains one of the most compelling in all of developmental psychology.

[Xu, 2013, p. 167]

This excerpt describes Piaget’s classic experiment to measure object permanence: An adult shows an infant an interesting toy, covers it with a lightweight cloth, and observes the response. The results:

This research provides many practical suggestions. If young infants fuss because they see something they cannot have (keys, a cell phone, candy), caregivers are advised to put that coveted object out of sight. Fussing stops if object permanence has not yet appeared.

By contrast, for toddlers, hiding a forbidden object is not enough. It must be securely locked up or discarded, lest the child later retrieve it, climbing onto the kitchen counter or under the bathroom sink to do so. Since object permanence develops gradually, peek-a-boo is too advanced in the first months, but it is fun just about the time that object permanence is new. As comprehension of hidden objects matures, peek-a-boo becomes boring, but hide-and-seek becomes fun. Again, take into account the age of the child: At first hide-and-seek must be quick and simple, with the giggling child hiding in the same obvious place again and again. After a few years, the game can become more elaborate (longer waiting, more imaginative hiding).

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Piaget believed that failure to search before 8 months meant that infants had no concept of object permanence—that “out of sight” literally means “out of mind.” That belief has been questioned. As one researcher points out, “Amid his acute observation and brilliant theorizing, Piaget … mistook infants’ motor incompetence for conceptual incompetence” (Mandler, 2004, p. 17).

A series of clever experiments in which objects seemed to disappear behind a screen while researchers traced babies’ eye movements and brain activity revealed that long before 8 months, infants are surprised if an object vanishes (Baillargeon & DeVos, 1991; Spelke, 1993). The idea that such surprise indicates object permanence is accepted by some scientists, who believe that “infants as young as 2 and 3 months of age can represent fully hidden objects” (Cohen & Cashon, 2006, p. 224). Other scientists are not convinced (Mareschal & Kaufman, 2012).

Further research on object permanence continues to raise questions and produce surprises. For instance, many other creatures (cats, monkeys, dogs, birds) develop object permanence at younger ages than Piaget found. The animal ability seems to be innate, not learned, as wolves can develop it as well as dogs—but neither is adept at “invisible” displacement, as when an object is moved by a hand underneath a cloth that covers it (Fiset & Plourde, 2013). At a certain age, children figure this out, but dogs do not.

In their second year, infants start experimenting in thought and deed—or, rather, in the opposite sequence, deed and thought. They act first (stage five) and think later (stage six).

Tertiary circular reactions begin when 1-year-olds take independent actions to discover the properties of other people, animals, and things. Infants no longer respond only to their own bodies (primary reactions) or to other people or objects (secondary reactions). Their cognition is more like a spiral than a closed circle, increasingly creative with each discovery.

Piaget’s stage five (ages 12 to 18 months), new means through active experimentation, builds on the accomplishments of stage four. Now goal-directed and purposeful activities become more expansive.

Toddlers delight in squeezing all the toothpaste out of the tube, drawing on the wall, or uncovering an anthill—activities they have never seen an adult do. Piaget referred to the stage-five toddler as a “little scientist” who “experiments in order to see.” Their research method is trial and error. Their devotion to discovery is familiar to every adult scientist—and to every parent. Protection needed.

Finally, in the sixth stage (ages 18 to 24 months), toddlers use mental combinations, intellectual experimentation via imagination that can supersede the active experimentation of stage five. Because they combine ideas, stage-six toddlers think about consequences, hesitating a moment before yanking the cat’s tail or dropping a raw egg on the floor.

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Thus, the stage-six sequence may begin with thought followed by action. Of course, the urge to explore may overtake caution: Things that are truly dangerous (cleaning fluids, swimming pools, open windows) need to be locked and gated.

The ability to combine ideas allows stage six toddlers to pretend. For instance, they know that a doll is not a real baby, but they can belt it into a stroller and take it for a walk. At 22 months, my grandson gave me imaginary “shoe ice cream” and laughed when I pretended to eat it.

Piaget describes another stage-six intellectual accomplishment involving both thinking and memory. Deferred imitation occurs when infants copy behavior they noticed hours or even days earlier (Piaget, 1962/2013). Piaget described his daughter, Jacqueline, who observed another child

who got into a terrible temper. He screamed as he tried to get out of a playpen and pushed it backward, stamping his feet. Jacqueline stood watching him in amazement, never having witnessed such a scene before. The next day, she herself screamed in her playpen and tried to move it, stamping her foot lightly several times in succession.

[Piaget, 1962, p. 63].

Despite several valid criticisms of Piaget’s work, he was correct in many ways. Infancy is a time for several distinct advances in cognition, and each new stage described by Piaget coincides with significant new connections in brain networks and functions. Piaget was right to describe babies as avid and active learners who “learn so fast and so well” (Xu & Kushnir, 2013, p. 28). His main mistake was underestimating how rapidly their learning occurs.

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