Piaget’s Stage Theory of Cognitive Development[

In Chapter 7, we saw how the ability of chimpanzees to solve two-choice visual discrimination problems improved gradually over the course of 300 problems. At the end, the chimp appeared to solve the problems in a qualitatively different manner. Rather than observing gradual improvement across the first six trials of each new problem, the chimp would jump from chance to perfect performance on the second trial (Harlow, 1949). One might conclude, it transitioned from an “incremental” stage to a “hypothesis-testing” stage of development. The name of the stage is descriptive of the performance, not explanatory. The explanation lies in the history of exposure to examples of the same type of problem. Although heredity and environment interact gradually and incrementally, sometimes the behavioral effect appears to constitute a qualitative change in the individual. The ability to comprehend language and speak result from physical development of the infant’s brain and speech organs, improved ability to imitate, and continual exposure to vocalizations.

Jean Piaget, a Swiss psychologist, proposed an influential theory of cognitive development from birth through adulthood (Piaget, 1928; 1952; 1962; Piaget & Inhelder, 1973). Piaget was an example of a stage theorist. Stage theory describes human development as a fixed sequence of capabilities resulting in qualitatively different ways of responding to the world. Piaget describes cognitive development as the continual modification (i.e., accommodation ) of schemas based on the incorporation (i.e., assimilation ) of new knowledge.  Piaget applied the overarching principles of assimilation, accommodation, and schema development to integrate the cumulative interactive effects of heredity and experience as the child ages and advances through the different stages.

The sensorimotor and pre-operational stages last from infancy through preschool and the early grades. During the sensorimotor stage (from approximately birth to two years) the child is preverbal, learning the relationships between sensory (e.g., visual and auditory) stimuli and movement. During the pre-operational stage , the child is able to use language to acquire skills and knowledge.  Interacting with a child that speaks is fundamentally different than interacting with a non-verbal child. Piaget’s distinction between non-verbal (sensorimotor) and verbal (pre-operational) stages seems appropriate and important. A child is able to learn in a qualitatively different way once acquiring speech.  We need to be careful, however, in how we interpret the meaning of a stage of development. It is one thing to describe the child as behaving as though being in a particular stage and a very different thing to offer the stage as an explanation for behavior. You might recognize this as another example of a pseudo-explanation. Why does the child speak? Because she/he is in the pre-operational stage. How do you know she/he is in the pre-operational stage? Because she/he speaks.

The newborn is able to sense the environment and emit a variety of responses. Whether in the rainforest or at home, as the newborn turns its head it will observe that some objects are stationary and others move. Some of the moving objects make sounds and others do not. Some of the objects feel soft and cuddly whereas others are hard. One of the soft moving objects makes sounds and sometimes approaches and holds the infant while placing its lips near something soft. This soft object can be sucked, resulting in the availability of a substance which can be tasted and smelled. The newborn’s initial schemas will most likely center around these external environmental stimuli and the internal sensations associated with basic survival drives such as eating and terminating discomfort. Eventually, some objects will be incorporated within a schema (e.g., objects that do not move), others might require modification of a schema (e.g., objects that can be moved and placed in the newborn’s tiny fingers), while others may require creation of an additional schema (e.g., round objects that move if simply touched). Gradually, concepts will be acquired (e.g., flat objects, round objects, heavy objects, light objects, soft moving objects that make noise and provide food, moving objects that make noise and bathe the infant, other similar looking moving objects that are usually present, other similar looking moving objects that are sometimes present, different looking moving objects that make different sounds and are usually present, etc.).

As the infant’s senses and motor abilities improve during the sensorimotor stage, it starts manipulating the environment and gradually acquires the ability to predict and control what happens. Piaget describes a three-stage sequence of circular reactions (i.e., repetitious behavior) taking place during this first, sensorimotor period of development.  Primary circular reactions appear to be repetition of a behavior for its own sake, or perhaps the resultant sensations. Secondary circular reactions consist of the types of behavior demonstrated by Rovee-Colier where the infant repeats an act resulting in a specific environmental effect. Tertiary circular reactions appear to involve attempts by the infant to produce the same environmental effect with different responses. Such attempts typically start to appear at about eight months of age and constitute the first examples of “experimentation.”

In addition to learning that she/he exists as an independent object, Piaget felt that an important concept acquired in the sensorimotor period is object permanence . Initially, children act as though once objects disappear from view they no longer exist; that is, “out of sight, out of mind.” Evidence suggests that children as young as 3-1/2 months old behave as though they understand object permanence. This is inferred from the fact that they look longer at events which turn out different than they apparently anticipated (Baillargeon & DeVos, 1991). For example, it has been shown that young infants will gaze longer at an impossible event (e.g., a toy train appearing to move through a block rather than hitting it (see below) than at a possible event.

Piaget suggested that, at about seven years of age, children advance from the pre-operational stage to the stage of concrete operations . It is at this time that the child appears to understand how certain operations can transform the appearance of objects but not their fundamental characteristics. As shown in the previous video, Piaget developed ingenious tasks for assessing this ability through the demonstration of conservation of number, mass, and liquid volume .  Here is another video showing developmental changes in children’s understanding of conservation of number, length and volume.

The following video describes Piaget’s sequence of four distinct stages of cognitive development.

If you first show a pre-operational child the two rows of five coins lined up so they match (a) and then spread out one of the rows (b) while they are watching , the longer row will be described as having more. They do not yet understand that the operation of moving the objects does not change the quantity. Similarly, a pre-operational child is likely to say that if one of two same-sized balls of clay is rolled into a sausage, it is now larger; or if one of two same-sized glasses containing the same amount of water is poured into a narrower but taller glass, it now has more. Children responding correctly are considered to have advanced to the stage of concrete operations. They understand how the concept of reversibility applies to the operations performed on the row of coins, clay, and liquid. The coins can be moved back to their original positions, the clay sausage rolled back into a ball, and the water poured back into the original glass.

To demonstrate another difference between a pre-operational child and one in the concrete operations stage, Piaget developed a task to determine the ability to perceive someone else’s perspective, as shown in the video.  The child was shown a realistic model of a scene including a mountain, toy animals, and plants. The young pre-operational boy only sees the scene from his own perspective. The older boy in the stage of concrete operations is able to imagine the scene from the adult’s position. Piaget and others describe the young boy’s behavior as reflecting egocentrism.

Piaget’s stages describe a progression in the child’s ability to use and manipulate symbols (i.e., to “think”). During the pre-operational stage the child is able to use words to symbolically represent objects and events. During the sensorimotor stage the child is restricted to symbols representing the structuralist’s three basic elements of consciousness; sensations, images, and emotions.

You might be wondering what it means to symbolically represent objects and events in the absence of language. In classic research, Walter Hunter (2013), a student of Harvey Carr’s (one of the early functionalists), tested to see whether his daughter and different animals could symbolically represent the location of an object. The procedure involved a small maze where a light could go on behind one of three “doorways.” If the subject went through the lit doorway, there was food present. There was no food behind the other doorways. This is a simple task for most animals to learn. However, if the light was turned on and then off, a rat could only go to the correct doorway if it oriented itself while the light was still on. Then, it would literally “follow its nose.” If the rat was spun around and released after the light went off, it performed at chance. Raccoons, chimpanzees, and Hunter’s daughter, went to the correct location even though there was no longer an external cue (i.e., light) to guide them. Hunter inferred from this behavior, that these subjects must have symbolically stored information concerning the prior location of the light in order to go to the correct doorway. This ability would have important survival value. For example, if an animal that is not hungry noticed food in a particular location, it would increase the likelihood of survival if it could return to that location when hungry. In addition, this test permitted Hunter to know when he needed to keep his eye on the family cookie jar!

During the concrete operations stage, the child is not only able to symbolically represent objects and events, but is also able to imagine manipulating concrete (i.e., observable) objects and events. The child can imagine moving the coins, squeezing the clay, pouring liquid from one container into another, or moving around the scene of the mountain. Piaget believed his final stage, formal operations , was reached between 12 and 15 years of age (Piaget, 1972; Piaget & Inhelder, 1958). The more adult-like teenager is able to imagine manipulating abstract concepts. For example, without looking at actual objects, an adolescent could be asked “If A is larger than B and B is larger than C, must A be larger than C?” She/he can imagine multiple examples fulfilling the requirements of the statements and arrive at the correct answer. The ability to mentally manipulate abstractions underlies logical thinking, scientific hypothesis testing, and every day problem-solving. The teenager can now execute all the stages of the problem-solving process symbolically: consider how things are, consider how she/he would like them to be, list optional solutions, evaluate the short- and long-term consequences of the different strategies, and arrive at a potential solution.

Piaget’s theory of cognitive development has been extremely influential and generated an enormous amount of empirical research. Piaget, himself, was a gifted child with an early interest in biology. He published several articles by the age of 15! A little known fact is that soon after receiving his doctorate, Piaget moved to Paris and worked with Alfred Binet in constructing items for his seminal school readiness test. Piaget’s stage theory was influenced by the distinct types of errors children of different ages made to certain questions on this test. From these errors, Piaget inferred qualitatively different cognitive styles (pre-operational, concrete operations, and formal operations). Based on his early interests and later work, it is not surprising that the tasks Piaget developed to study cognitive development are oriented toward scientific thinking or that performance on these tasks correlates with school readiness and intelligence tests (Humphreys & Parsons, 1979).

Piaget has been criticized for basing his theory on the observation of a very small non-representative sample of individuals; his three precocious children and the children of highly-educated professionals. Research conducted with more representative samples has generally supported the sequence Piaget described in the ability to solve different types of problems. However, there is considerable variability in the ages at which different children demonstrate the characteristic behavior patterns of the different stages. For example, as previously cited, pre-verbal (i.e., sensorimotor stage) children can demonstrate object permanence (Baillargeon & DeVos, 1991). At the other end of Piaget’s developmental sequence, adults frequently lack or are inconsistent in their usage of formal operational thinking. Piaget (1972) himself recognized this inconsistency. He suggested that experiential differences with different domains of skills (e.g., physics, mathematics, philosophy, etc.) could result in concrete operational type performance in some situations and formal operational performance in others. In the next chapter, we will see that this same pattern of inconsistent performance across situations applies to other human personality characteristics in addition to cognitive style. Some have argued that Piaget fails to appreciate the underlying role of basic cognitive processes (e.g., short-term memory, processing speed, etc.) in movement from stage to stage as well as individual differences (Demetriou & Raftopoulos, 1999; Demetriou, Mouyi, & Spanoudis, 2010). It has been demonstrated that science training improves performance on the Piagetian tasks (Lawson, 1985). Such training effects suggest that movement through the stages is more reliant upon experience than Piaget implies.

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