The Making of the Mind: The Neuroscience of Human Nature (9 page)

The
ratchet effect
refers to the accumulation of innovations and modifications over multiple generations.
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Cultural traditions have the possibility of becoming more rich and complex as a result. Children in each generation learn from their parents about the traditions of the past. This cultural learning process serves as a ratchet to prevent the culture from slipping backward and losing the innovations of earlier generations. Of course, some insights, inventions, and ways of living are in fact lost over time, but the ratchet effect of children's cultural learning can succeed on the whole, at least for those cultures that show cumulative traditions. One clear example from prehistory to the present is the evolution of hammers. The design of hammers has changed repeatedly over thousands of years, “going from simple stones, to composite tools composed of a stone tied to a stick, to various types of modern metal hammers and even mechanical hammers.”
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The ratchet effect that accounts for the cumulative nature of cultural evolution thus depends on both innovation and learning. In the ratchet effect, one can see how an advanced social intelligence exploited the innovative capacities of an advanced system of working memory. Innovations arise from the fluid intelligence made possible by the executive attention of human working memory. Children can then learn of past innovations from their parents and other elders in their community through a process of imitation and practice, or at times through direct instruction. Imitative and instructed learning serve as ratchets that hold fast the innovations of the previous generation. Through them, these innovations can be faithfully brought into working memory among members of the current generation. This allows further discoveries and further modifications that can then be passed on to the next generation. Without the ratchet of cultural learning, the discoveries of human beings would simply die with them. Instead, creative individuals living now can in a sense collaborate with inventors who came before by taking up where they left off to innovate further.

If one thinks of biological evolution as the slow, measured way of creating life in general and the human brain in particular, then cultural evolution was the move to the fast lane. The modern human mind benefited from an entirely
new means of evolving through inheritance of past adaptations. This new means of cultural inheritance rushed like a mountain stream past the glacial pace of biological inheritance.

CULTURE MOLDS THE MIND

Whereas human populations are largely identical to one another at the level of the human genome, cultural differences in thought, values, beliefs, and behaviors are enormous. Ethnic differences are so potent that they often blind us to our common humanity. Although all human beings are born with the same nervous system and brain, the culture in which an individual is raised molds the mind from birth and throughout the lifespan. Although we come into the world equipped to learn the sounds used in any human language, the mind becomes attuned to hearing and producing only those phonological segments that constitute the phonemes of one's native language. Although all children are capable of using nonverbal gestures and expressions to communicate, cultures differ in the extent of use and degree of animation of body language. In a similar way, the acceptable physical proximity while conversing and the expectation of social hugs and kisses while greeting vary with culture. Or, consider the variations in what people find appetizing to eat for dinner. An American typically eats pork and beef, whereas an Israelis might shun pork or an Indian might shun beef on religious grounds. Americans and Europeans are squeamish about snake, whereas the Chinese enjoy it as well as pork and beef. Yet Europeans may enjoy eels and snails, neither of which is marketed to Americans, despite their tradition for consuming raw oysters. None of these ethnic variations can be accounted for in the biology of the brain or stomach—they reflect instead the shaping of the human mind by the social world into which we are born.

Psychologists have documented culturally induced differences in basic mental processes by comparing one demographic or ethnic group to another. Much of this research has contrasted East Asians with European North Americans to specify these differences at a detailed level.
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Americans who are descendants of immigrants from Europe belong to a culture that stresses individualism, self-reliance, and independence. By contrast, East Asian cultures
stress collectivist ways of thinking and the interdependence of group members. Collectivist thinking places the needs of the group as a whole above the needs of the individual. These culturally mediated differences in how the mind functions permeate daily life. When interpersonal conflicts arise, Americans often adopt confrontational approaches, including even filing a lawsuit—the sledgehammer of direct confrontation. East Asians, by contrast, seek mediation and accommodation as a way to resolve conflicts with a minimum of animosity among the parties involved. Marketing strategies differ, with advertisements appealing to harmony and benefits for the group as a whole in East Asia while ads for Americans appeal to a desire for competitive advantage and individual uniqueness. American mothers expect greater independence in their children at a young age compared with East Asian mothers. In school, the East Asian teacher is more likely to address communication to the class as a whole whereas American teachers tend to communicate directly to the individual student.

As part of normal cognitive development, the human mind constructs a concept of the self during childhood and adolescence. Relative to Americans, when young adults in East Asia are asked to describe the self, they generally make more statements about the groups to which they belong and the ways in which the self is interdependent on others. East Asian culture “prescribes devaluation of one's distinctive personal strengths that are unrelated to or would even hinder actualization of collective goals…and a strong motivation to avoid failures that would reflect badly on the group.”
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By contrast, the independence stressed by Western culture biases Americans toward “self-enhancement (viewing one's personal attributes as better than they really are), unrealistic optimism (perceiving the self as more invulnerable and more likely to experience positive events than it really is), and self-affirmation (justifying one's personal choices).”
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The power of culture to mold the mind can also be observed in those who migrate to a new culture. Although one's native culture is never left behind completely, immigrants must undergo a process of acculturation and change in response to their exposure to a new language, new ways of living, and new values and beliefs. The nature of acculturation varies markedly with the age of the immigrant.
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Young children are far more flexible in identifying
with the receiving culture and learning its practices, including its language. Migrating as an adolescent or an adult implies leaving behind a culture that has already profoundly sculpted the individual's mind. This is especially true of older adults for whom it is easier to retain the language and identify of the heritage culture instead of attempting to acquire the new one. Ethnic enclaves within the receiving culture offer a buffer and allow retention of the heritage culture in large measure. For example, in the United States, parts of Miami, the South Bronx, and Chinatown neighborhoods in various cities offer protective ethnic enclaves. The heritage culture within them is so strong that even the second-generation immigrants—those born into American culture—can be influenced to retain the culture of their parents.

The advanced social intelligence of human beings provides the obvious explanation for why one's native culture imprints on the mind. The human brain is designed to attend to the behaviors and minds of others; it is designed to learn by observation and imitation. All this is made easier by the highly immature state of the body and, in particular, the organ of the brain at birth. Unlike many other mammals and primates, human beings are altricial and completely dependent on parental care during infancy. Unlike, say, the prococial horse, ready to stand at birth, the altricial human being is utterly helpless. As can be seen in the following facts, the immaturity of the brain at birth is especially significant for the impact that culture has on the developing mind.
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Whereas the sensory areas mature early in development, the higher cortical areas mature later, after exposure to environmental influences. The brain is still growing throughout childhood, when the individual is largely dependent on and immersed in the cultural environment of the parents; the brain does not reach adult size until around puberty. Finally, the prefrontal cortex is not fully mature until young adulthood, after two decades of cultural influence.

Culture can thus imprint upon the developing human brain and sculpt an individual's mind to fit into an ethnic group. The brain—in an immature, still developing state—is bathed in the physical and social environment of the child's immediate world throughout infancy, childhood, adolescence, and even young adulthood. Just as the fetal environment of the mother's womb bathed the brain during prenatal development, so, too, does the cultural world into which the child is born. Nature has left much of human brain development
for later, after birth, when nurture can shape the outcome rather than leaving it to a genetically predetermined plan. The language, social norms, and ways of life of the child's native culture are thus melded into the neural circuitry. Because human brain maturation is delayed, the advanced social intelligence that we have inherited in our brain structure and functioning produces a mind determined as much by culture as by DNA.

ADAPTATIONS FOR CULTURAL LEARNING

By the age of nine to twelve months, infants are normally able to share eye contact with another person.
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Eye contact between the mother, father, or other caregiver and the infant becomes a medium for sharing the same focus of attention. For example, if a parent looks at and points to a cup on the tray of a daughter's high chair and the infant directs her gaze at the cup at the same time, the parent and child are in essence joining minds for a moment. Both are perceiving the cup and holding it for a while in working memory, allowing the possibility of the infant learning something new from the parent. The parent might say “cup” or “this is a cup” or “do you want your cup.” In each case, there is an opportunity for the child to learn the name of the object held now in the focus of attention.

Joint attention narrows to one the number of possible objects in the room that
cup
could refer to, without which the child would be lost trying to figure out whether
cup
refers to the tray, the floor, the spoon next to the cup, and so on. Learning the names of objects should thus be greatly aided by joint attention. In fact, the ability of infants to follow the gaze of an adult at the age of ten to eleven months is predictive of fluency with language at eighteen months of age.
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This, then, is one illustration of how the infant's response to the caregiver's focus of attention is the basis for learning culture through social interaction with another, more knowledgeable human being.

Infants also initiate joint attention to share with others what interests them. A child might point to an object in order to attract the parent's attention to it. Or the child might gaze at the object and then look into the parent's eyes and then look back at the object. The child might repeat this several times in order to establish joint attention.

Developmental psychologists have learned that such initiation of joint attention is surprisingly not closely connected with simply responding to the gaze and gestures of the caregiver. The two ways for minds to meet are mediated by separate systems of attention in the neocortex.
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Responding to joint attention is mediated by the parietal and temporal lobes in the posterior regions of the brain. The frontal lobe of the brain provides the neural networks for an anterior attention system that can initiate gestures and control gaze direction. It is part of the executive attention component of working memory, and it develops at a slower pace relative to the posterior attention system.

Recognition of Intentional Agents

Importantly, joint attention requires the capacity to hold in mind a triadic relationship of the child, the adult, and the object or event being attended to by both. By six months of age, infants can interact in a dyad with an object or with another person. Grasping a cup, for example, involves only the child and the object. Or making eye contact with the adult involves only the child and adult. But in joint attention, all three elements of the triangle are represented; this triadic capability emerges later in cognitive development, between nine to twelve months. Within this four-month window, almost 80 percent of infants show numerous signs of skill in joint attention.
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Not only gaze following, but also point following, imitation of acts, and the use of gestures to make declarations of facts and imperative demands all coalesce during this interval.

Why does joint attention begin to emerge at nine months rather than earlier? Michael Tomasello argues that “infants begin to engage in joint attentional interactions when they begin to understand other persons as intentional agents like the self,” as “animate beings who have goals and who make active choices among behavioral means for attaining these goals, including active choices in what to pay attention to in pursuing those goals.”
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The infant needs to grasp that the adult has goals, just like he or she does, and that the adult can make choices about how to attain these goals—in other words, the adult has a mind just as a child has a mind. As cognitive development proceeds, infants and young children develop increasingly sophisticated understandings about the minds of others. The process is only just beginning at the end of the first year of life.