Chapter 2
The Infant’s Undifferentiated World
Piaget divided cognitive development into four periods. He called them the Sensorimotor Period (0-2 years), 19 the Preoperational Period (2-7 years), the Concrete Operational Period (8-11 years), and the Formal Operational Period (12 years-adolescence or early adulthood).
In this chapter, I describe Piaget’s first four sensorimotor stages and Piaget’s interpretation of the quality of the child’s understanding —the organization of her cognition —during each stage. To me, the shift in cognition that takes place between Stage 3 and Stage 4 is a fundamental reorganization. The importance of this shift will become clear in chapter 3, when I explain how complete myelination of two sensory tracts to the brain assists Stage 3 to Stage 4 reorganization.
The Sensorimotor Period consists of six stages. 20 The schemes of the Sensorimotor Period begin in a very undifferentiated and global state, and, in stages, they restructure themselves as they interact with the world via the child’s sensory and motor systems. These stages culminate in Stage 6 (16-24 months), when the mental-image scheme of an object is basically differentiated from the perception scheme of that object, and when schemes of different objects, including the self as an object, are basically differentiated from one another.
As I noted in chapter 1, not everyone agrees that such cognitive differentiations occur slowly, o r that they occur in steps. Some researchers and theoreticians assert that even newborns understand the difference between different objects, including the difference between the self and other objects. I discuss this assertion later in this chapter, and in chapters 4 and 5.
Stages 1 to 3: The Cumulative Mode
In Stage 1 of the Sensorimotor Period (0-1 month), children practice their reflexes. Gradually they get better at sucking, at grasping, and at following a moving light with their eyes.
Although they are endowed with the sucking reflex, newborns vary in their ability to suckle the breast effectively. Piaget charted this ability primarily in his son, who, in the first few hours after birth, suckled effectively when his mouth and tongue contacted the nipple. By day 9, he differentiated objects that he encountered with his mouth. He rejected a cloth, but sucked his own hand. When his cheek was touched, he searched in the direction of the touch, and became more precise and rapid in finding the nipple. On day 20, he sucked on the skin of the breast briefly, then moved, sucked briefly, then moved again until he located the nipple.
That same day, Piaget offered his finger to his son, who was moderately hungry. After sucking for a few seconds, his son rejected the finger. He did this twice, but then sucked for several minutes, until Piaget removed his finger. The same day and the following day, Piaget’s son sucked his thumb contentedly for extended periods. To the infant, it appears that there is little difference between the schemes: sucking-the-breast-and-swallowing-milk, sucking-his-own-thumb-and-swallowing-saliva, and sucking-someone-else’s-finger-and-swallowing-saliva.
Only initially, when the infant rejects the foreign finger, does the infant appear to differentiate the finger from a nipple. Nonetheless, this initial behavior indicates that, to some extent and at least temporarily, the sucking-scheme-when-hungry is differentiated from the sucking-scheme-when-not-hungry. 21
The disquiet —an emotion or proto-emotion —that accompanies the hunger probably guides the differentiation —the distinction between sucking a finger and sucking the nipple. Emotion, which is closely tied to the physiology of the organism, may interrupt what is not working —in this case, sucking on a finger when hungry. It is appropriate to think of schemes as being cognitive-emotional at least as early as day 20. Indeed, Piaget argued that cognition is never devoid of emotion, and emotion is never devoid of cognition.
The infant’s behavior on day 25 and 26 also indicated some scheme differentiation, based on whether he was hungry or not. On day 25, when he was not particularly hungry, he made only a cursory attempt to find the nipple. The following day, when he was very hungry, he invoked all his skills, including his new ability to raise his head a bit, in his search for the nipple.
So, added to what is intrinsic to sucking —e.g. proprioception from the mouth or swallowing —and what is adventitious —e.g. warmth of an adjacent body or ambient light —the sucking scheme includes improved abilities to search and find the nipple plus, when hungry, some temporary distinction of objects —the finger, breast and nipple —and some states that an outside observer would ascribe to the self —satisfaction and dissatisfaction.
In Stages 2 and 3 the reflexes appear to open up, as the infant repeats adventitious sensorimotor encounters. For example, in Stage 2 (2-4 months), an infant who has, by chance, extended her arm and grasped the edge of a blanket may grasp and let go, grasp and let go. The scheme of grasping assimilates the scheme of extending the arm. It might be more appropriate to say that the grasping scheme and the extending-the-arm scheme s assimilate each other. Activation of touch, of proprioception, and of motor control neuronal circuits that are involved in grasping, as well as, activation of proprioception and of motor control neuronal circuits that is involved in extending the arm are all part of the Stage-2 scheme. Similarly in Stage 2, an infant may repeatedly thrust out and suck her tongue or a bolus of saliva. The sucking scheme and the thrusting or extruding scheme assimilate each other.
The object, the tongue or the bolus of saliva, like the extruding and sucking are all part of the sucking scheme, not separate objects, and not one belonging more to the outside, while the other belonging more to the self.
The behavior of infants in Stage 3 (5-8 months) looks as if it were intentional —not automatic. If an infant happens to strike a hanging object with her hand or foot, causing it to swing or to make a sound, or if she strikes her crib with the same result, she repeatedly strikes and watches or listens. Striking schemes and looking or listening schemes assimilate each other. The child may then vary her striking as she watches or listens. The two different sensorimotor schemes accommodate each other.
Sated with this activity, a Stage-3 child may make a swinging movement with her hand —appearing to imitate the swinging of the hanging object —or make an abbreviated striking movement. It is as if the child were saying, "I could make it happen again if I wanted to. " If a child at this age were thinking this, she would be intending her actions. This would mean that the 6- or 7-month-old child understood certain self-object relationships —for example, that she was causing the hanging object to swing. If she were intending her actions, or if she understood that she was causing the hanging object to swing, she would be differentiating the scheme of her self from the scheme of another object —that is, the hanging object.
Piaget questioned whether this was the case. He did several experiments to see if the Stage-3 child understood how the scheme of the self was related to the scheme of another object —that is, to see if the child understood that her striking action caused the movement of the object. In one experiment, he found that if the child was accustomed to strike with her arm or leg to cause an object to move or to rattle, she would strike when she saw the object, even when the object was too far away to be affected. In another experiment, he tied a string to his child’s arm and connected the other end of the string to a suspended object. She had great fun moving her arm and watching the object swing. He found, however, that whether the string was made lax or taut had no effect on the child’s action in response to seeing that object. She continued to move her arm when she saw the object. Further, he found that each child had her own repertoire. While lying in a crib, one child arched her back or rolled her head, which caused an object that was attached to the crib to move. Another child struck out with her arm; another with a leg or both legs. When a new object was presented, each child went through her own particular routine, regardless of which object was presented, whether the object was out of reach, and whether the child was physically connected to the object.
Piaget concluded that in Stage 3, children are merely striking while watching or listening, and watching or listening while striking. That is, he concluded that the watching or listening schemes are assimilated to the striking scheme, and that the striking scheme is assimilated to the watching or listening schemes —that children in Stage 3 do not understand their relationships to objects.
In a different type of experiment, Piaget placed a toy under a screen while the Stage-3 child watched. It should be understood that when I use the word toyin reference to Piaget’s experiments, I intend toy to represent any object that interests a child. He used various toys, e.g. a watch or a ducky. If part of the toy was visible, the Stage-3 child retrieved the toy. If the screen covered the toy entirely, the child did not search under the screen unless her hand grazed the toy, or unless she was making a grasping movement as the toy disappeared. Instead, the child might whimper or look at Piaget’s hand.
In Stage 3, the child’s hand touching the toy and her watching Piaget’s hand are both part of the scheme of the toy, as is seeing a piece of the toy protruding from under the screen. To the child, touch, proprioception, and motor control of her hands, as well as vision, proprioception, and motor control of her eyes, are all part of the scheme of the toy at this stage. There is no clear differentiation of the schemes of different objects —the toy and Piaget’s hand or the toy and the self that touches it or that makes a grasping movement.
Piaget proposed that in Stage 3, when a toy disappears behind a screen, the scheme of the toy enters the void. By entering the void, Piaget meant that the Stage-3 child’s world is one in which things —such as toys and persons —materialize and dematerialize. Some part of the child’s scheme, however, must still be active after the object disappears, since Piaget reported that after the toy disappeared, the child whimpered and/or looked at Piaget’s hand.
What is it like to live in a Stage-3 world, a world in which schemes of different objects are not distinct from one another? Piaget referred to the infant’s repeated striking of an object, while watching it or listening to it, as making interesting spectacles last. For the infant, perhaps this is like watching and listening to semirandom fireworks, while experiencing activations from proprioception and fluctuating motor control, plus some pleasant excitement accompanying this sensory and motor spectacle.
Rochat (2001) wrote that Piaget, like William James, the father of American psychology, thought of the infant’s global and undifferentiated state as a booming, buzzing confusion. But to experience confusion, one must have a sense of a unity that is lost. To slip from focus to focus, or from scene to scene, is not necessarily any more confusing than watching the landscape slip by from a moving train. In fact, Piaget’s scheme, undifferentiated and global as it is, assimilates that which suits it at its particular level of organization. Assimilation of what approximates an already-existing scheme provides organization, not disorganization —not William James’s booming, buzzing confusion. It is as if the infant has an agenda —the fitting of input into what the infant has already constructed. A booming, buzzing confusion is what adults would experience if they were to suddenly experience the world as the Stage-3 child does.
As the schemes of the first three stages assimilate and accommodate, they tend to enlarge the child’s repertoire, as when the child sucks different objects or strikes different objects to produce new spectacles. Even when a child rejects a behavior —for example, when the hungry child refuses to suck a finger —the child’s repertoire may be thought of as enlarged. Being hungry and halting sucking becomes part of the sucking scheme. The sucking scheme now includes a possible negative valence under certain circumstances. 22
In Stage 4, the ordering or articulation of schemes begins. In Stage 4, two new types of behavior make their appearance. These two new types of behavior indicate that the child is beginning to make distinctions between the schemes of different objects, including the self as an object.
A More Differentiated Way of Understanding the World
In Stage 4 (8-12 months), children search for a toy after watching it being hidden under a screen when no part of the toy is visible. They no longer have to see a part of the toy, or to have grazed the toy with a hand, or to have been in the process of making a grasping movement. The Stage-4 toy scheme is more distinct from the Stage-3 self scheme’s touching the toy, making a grasping movement, or seeing a piece of the toy. In addition, the Stage-4 toy scheme is more distinct from the scheme of other objects —for example, the hand scheme that placed the toy under the screen.
A second type of behavior also indicates that the child is beginning to distinguish between schemes of different objects. In steps, a Stage-4 child learns to set aside an object to get at a more interesting object. For example, when Piaget’s son attempted to reach a toy, he depressed an intervening pillow. This permitted him to retrieve the toy. When presented with the same problem, he depressed the pillow again. About 2 weeks later, he struck aside intervening objects to obtain a desired object. Apparently he distinguished between simultaneously active schemes of different objects —for example, the pillow and the toy.
The distinctions between simultaneously active schemes of different objects are far from absolute in Stage 4. But the examples noted above indicate that the child has begun to make such distinctions. The child both differentiates and articulates simultaneously active schemes —the scheme of the screen and the scheme of the invisible toy, and the scheme of an intervening object to be acted upon before acting upon the scheme of a desired object. The screen scheme that is lifted is differentiated from the toy scheme, just as the intervening-object scheme is differentiated from the desired-object scheme. From the same behaviors, we may conclude that these schemes are articulated —connected to each other by a particular relationship —no longer merely assimilated to each other. The child must lift the screen or strike the intervening object before grasping the toy.
Intention, in the sense of purposefulness, is clearly manifest in such selections. The child has begun to distinguish between the scheme of the self and the schemes of other objects. In Stage 3, touching the toy, making a grasping motion, and even having to see a part of the toy are parts of the scheme of the nascent self. In Stage 4, when the child searches for the toy without touching or seeing it or without making a grasping motion, then those parts of the scheme of what becomes parts of this somewhat differentiated self —touching, seeing, or grasping motion —are no longer part of the scheme of the toy.
Each behavior also includes some differentiation within the self-scheme. Actions are ordered. Uncovering is done before grasping. Striking or pushing aside is also done before grasping.
There is little argument that an infant will search under a screen for a toy at about 9 months and not much earlier (Meltzoff, 1996). However, some investigators (Baillargeon, 1987; Baillargeon, Spelke, & Wasserman, 1985) have contended that the infant understands the distinctions between objects and the solidity of objects long before he searches under a screen for an object. They used differential looking-at-an-object as a measure of understanding distinctions between objects, rather than search-for-an-object as a measure of such understanding.
I return to Baillargeon and Spelke’s contention in chapter 4, where I point to an observation by Piaget that indicates that, as late as Stage 5, children do not understand the solidity of objects. Here suffice it to say, that the difficulty involved in control of reaching is not likely to account for the discrepancy between Baillargeon and Spelke’s position and Piaget’s. As I pointed out in chapter 1, infants will reach for a ball 3 to 4 months earlier than Stage 4 —that is, in Stage 3. Also, Stage-3 infants will reach for a toy if a piece of the toy is visible, as I have just explained. It is clear that Stage-3 infants can direct their reaching —albeit clumsily. Like Piaget, I contend that Stage-3 infants do not search under a screen for a toy because they do not understand that the toy is under the screen, once the toy is fully hidden.
Using a split-screen testing method that depended on looking behavior, Meltzoff and Moore (1999) provided more evidence that self-object differentiation begins in Stage 4, as Piaget had proposed. In Meltzoff and Moore’s test, a toy passes behind screen 1, is not seen in the gap between screen 1 and screen 2, but then emerges from behind screen 2. If the trajectory of the toy and the features of the toy —for example, its shape —remain unchanged, 9-month-olds look at the edges of the first screen "as if peering around it to find the hidden [toy]" (p. 68). Five-month-olds, presumably in Stage 3, did not do this. The authors concluded that "two widely divergent response systems, visual and manual, yield the same story" (p. 68).
Using looking behavior as a measure, Meltzoff and Moore confirmed Piaget’s findings that the child first clearly differentiates schemes of different objects —the screen and the toy —at about 9 months of age. However, they cited the 9-month-olds’ behavior as evidence of object permanence. The behavior does indicate a certain sense of object permanence; the child has some notion that the object exists without having to see a part of the object and without acting on it with her hand. However, in keeping with Piaget’s view, I contend that the child’s sense of object permanence is still not well differentiated at 9 months.
The Differentiation Is Incomplete
In Stage 4, the child has begun to distinguish between simultaneously active schemes of different objects. But the boundaries between these schemes remain permeable. Piaget found that a child who had previously found a toy in a particular location, and who now watched the toy being hidden in a new location, might first search for the toy in the old location. This behavior is known as the A-not-B error. Evidently, the Stage-4 child’s scheme of an object is not distinct from his or her scheme of past successful action on that object. 23
Thelen et al. (2001) argued that the A-not-B error is "not about an object concept per se… that ’knowing’ is perception, acting and remembering, as they evolve over time" (p. 4). Thelen and her colleagues adopted a field theory model that takes into account many variables in motor planning. They referred to Stage-4 schemes as coupled looking, planning, reaching, and remembering in goal directed-actions —that is, as motor action patterns. Smith —one of Thelen’s associates —elicited the A-not-B error in 7- to 12-month-olds who lifted the lids on empty wells when the lids that covered the wells were the same color as the entire structure —that is, brown. The children lifted the lid whether it was made salient by hiding an object in the well or by calling attention to the lid. In emphasizing that Stage-4 schemes are motor action patterns, Thelen was arguing that these schemes are not representations at all —that they are justmotor action patterns. But the fact that children lift the lids on empty wells does not prove that children have no beginning object representations for different objects. A lid is an object in its own right.
Although the undifferentiated object schemes of Stages 1 to 3 are quite different from the more differentiated object schemes of the later stages, I wish to remind the reader that, to the infant, they are the object. In Stage 4, however, the object scheme that is the toy and the object scheme that is the screen are beginning to be distinct from each other. Further, although the schemes’ differentiation is limited, and Thelen’s view that Stage-4 schemes are merely action patterns notwithstanding, I will propose that Stage-4 schemes are conscious object representations. I discuss this issue at length in chapter 4.
The fact that the lid of a well is as much an object in its own right as a toy placed in a well is consistent with another of Piaget’s findings in Stage 4. When Piaget placed a matchbook on a platform, provided the platform was not too large, his child did not reach for the matchbook unless the platform was tilted and the matchbook slid. When Piaget placed a goblet on a platform, his child retrieved the goblet. Apparently the sets of edges of the matchbook and those of the goblet being distinct from the edges of the platform helped the child to differentiate the scheme of the matchbook and the scheme of the goblet from the scheme of the platform. But in the case of the matchbook, the movement of its edges relative to the edges of the platform was what made it possible for the child to distinguish between the schemes of these two objects.
Thus Thelen’s (2001) report that the child discriminates different lids of empty wells is not surprising, particularly if the lids move. Schemes of different lids are likely to be differentiated from each other, just as the scheme of the matchbook is differentiated from the scheme of the platform.
These observations involving objects and platforms serve to introduce my proposal that a particular type of neuroanatomic maturation would assist the cognitive shift from Stage 3 to Stage 4. I will discuss the mechanics of this shift in the next chapter.
19 All ages given here are approximate.
20 Unless otherwise indicated, all examples of Sensorimotor Period behavior cited here are drawn from Piaget’s trilogy (1954; 1962; 1963), which he regarded as one study. The examples that I cite are only a very few of the many examples that Piaget reported. Some of his observations were confined to only one of his three children. Most often, he studied all three children and varied the studies systematically before he concluded what characterized the child’s cognition during a particular stage of development.
21 Mostly, I will stay with Piaget’s language, although throughout the book, schememay be translated as activation of a neuronal circuit.
22 To record the "this" of "do this" as a part of the same scheme as "don’t do this," and just add a positive or negative valence —a yes or a no —is a more efficient way to process schemes than to have separate schemes for "do this" and "don’t do this. " In adults representation by opposites is a hallmark of unconscious processing. In rats, "extinction of long-term memory… is subserved by the same brain region that subserves the acquisition and consolidation of that same memory," (Berman and Dudai, 2001, p. 2419). Opposites have almost the same location s in the cerebral cortex. Further, measured by a functional MRI ( fMRI) in adult humans, the fusiform face area of the cortex —an area that is ordinarily activated by a picture of a face —is activated equally by the picture of a body with a blur where a face would be (Cox, Meyers, & Sinha, 2004). (The fMRI measures blood flow. Blood flow is increased in a brain region when the neurons of that region are more active. ) The face and its context —the face and what it is not, or what it is related to but distinct from —activate the same area of the cortex. As Schiller (1952, p. 207) put it, "To define a whole, we have to take into account what it is not, as well as what it is. "
23 Initially, investigators had difficulty repeating Piaget’s observation. Uzgiris and Hunt (1975) proposed a reliable method of testing for the A-not-B error. The investigator repeatedly hides a toy under a screen at point A until the child successfully searches twice under the screen at point A. Then, while the child watches, the experimenter hides the toy under a screen at point B. If the child searches first under the screen at A, the child has made the A-not-B error.
Using various versions of this method, the A-not-B error has been researched extensively in 7- to 12-month-olds. The findings are complex and their interpretation remains controversial. In my mind, it is possible that this method is not comparable to Piaget’s observation of the child’s spontaneous behavior, because the method invites perseveration —repetition of behavior that no longer makes sense. For an extensive review and commentaries, see Thelen et al. (2001).
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