Among these is the concept that the left and right hemispheres of the brain should be taught separately to maximize the effectiveness of learning. Another widely held misconception is that people use only 20 percent of their brains—with different percentage figures in different incarnations—and should be able to use more of it.
However, it is now known that these silent areas mediate higher cognitive functions that are not directly coupled to sensory or motor activity. Advances in neuroscience are confirming theoretical positions advanced by developmental psychology for a number of years, such as the importance of early experience in development Hunt, What is new, and therefore important for this volume, is the convergence of evidence from a number of scientific fields.
As the sciences of developmental psychology, cognitive psychology, and neuroscience, to name but three, have contributed vast numbers of research studies, details about learning and development have converged to form a more complete picture of how intellectual development occurs. Clarification of some of the mechanisms of learning by neuro-.
These technologies have allowed researchers to observe human learning processes directly. This chapter reviews key findings from neuroscience and cognitive science that are expanding knowledge of the mechanisms of human learning. Three main points guide the discussion in this chapter:.
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These structural changes alter the functional organization of the brain; in other words, learning organizes and reorganizes the brain. We first explain some basic concepts of neuroscience and new knowledge about brain development, including the effects of instruction and learning on the brain. We then look at language in learning as an example of the mind-brain connection. Lastly, we examine research on how memory is represented in the brain and its implications for learning. Brain development and psychological development involve continuous interactions between a child and the external environment—or, more accurately, a hierarchy of environments, extending from the level of the individual body cells to the most obvious boundary of the skin.
Greater understanding of the nature of this interactive process renders moot such questions as how much depends on genes and how much on environment.
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As various developmental researchers have suggested, this question is much like asking which contributes most to the area of a rectangle, its height or its width Eisenberg, ? Neuroscientists study the anatomy, physiology, chemistry, and molecular biology of the nervous system, with particular interest in how brain activity relates to behavior and learning. Several crucial questions about early learning particularly intrigue neuroscientists.
How does the brain develop? Are there stages of brain development?
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Are there critical periods when certain things must happen for the brain to develop normally? How is information encoded in the developing and the adult nervous systems? And perhaps most important: How does experience affect the brain? A nerve cell, or neuron, is a cell that receives information from other nerve cells or from the sensory organs and then projects that information to other nerve cells, while still other neurons project it back to the parts of the body that interact with the environment, such as the muscles.
Nerve cells are equipped with a cell body—a sort of metabolic heart—and an enormous treelike structure called the dendritic field, which is the input side of the neuron. Information comes into the cell from projections called axons. Most of the excitatory information comes into the cell from the dendritic field, often through tiny dendritic projections called spines.
The junctions through which information passes from one neuron to another are called synapses, which can be excitatory or inhibitory in nature. The neuron integrates the information it receives from all of its synapses and this determines its output. At birth, the human brain has in place only a relatively small proportion of the trillions of synapses it will eventually have; it gains about two-thirds of its adult size after birth. The rest of the synapses are formed after birth, and a portion of this process is guided by experience. Synaptic connections are added to the brain in two basic ways.
The first way is that synapses are overproduced, then selectively lost. Synapse overproduction and loss is a fundamental mechanism that the brain uses to incorporate information from experience. It tends to occur during the early periods of development. In the visual cortex—the area of the cerebral cortex of the brain that controls sight—a person has many more synapses at 6 months of age than at adulthood.
This is because more and more synapses are formed in the early months of life, then they disappear, sometimes in prodigious numbers. The time required for this phenomenon to run its course varies in different parts of the brain, from 2 to 3 years in the human visual cortex to 8 to 10 years in some parts of the frontal cortex. Some neuroscientists explain synapse formation by analogy to the art of sculpture. Classical artists working in marble created a sculpture by chiseling away unnecessary bits of stone until they achieved their final form.
The nervous system sets up a large number of connections; experience then plays on this network, selecting the appropriate connections and removing the inappropriate ones. What remains is a refined final form that constitutes the sensory and perhaps the cognitive bases for the later phases of development. The second method of synapse formation is through the addition of new synapses—like the artist who creates a sculpture by adding things together until the form is complete.
Unlike synapse overproduction and loss,.
This process is not only sensitive to experience, it is actually driven by experience. Synapse addition probably lies at the base of some, or even most, forms of memory. As discussed later in this chapter, the work of cognitive scientists and education researchers is contributing to our understanding of synapse addition. The role of experience in wiring the brain has been illuminated by research on the visual cortex in animals and humans. In adults, the inputs entering the brain from the two eyes terminate separately in adjacent regions of the visual cortex. Subsequently, the two inputs converge on the next set of neurons.
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People are not born with this neural pattern. But through the normal processes of seeing, the brain sorts things out. Neuroscientists discovered this phenomenon by studying humans with visual abnormalities, such as a cataract or a muscle irregularity that deviates the eye. If the eye is deprived of the appropriate visual experience at an early stage of development because of such abnormalities , it loses its ability to transmit visual information into the central nervous system. When the eye that was incapable of seeing at a very early age was corrected later, the correction alone did not help—the afflicted eye still could not see.
When researchers looked at the brains of monkeys in which similar kinds of experimental manipulations had been made, they found that the normal eye had captured a larger than average amount of neurons, and the impeded eye had correspondingly lost those connections. This phenomenon only occurs if an eye is prevented from experiencing normal vision very early in development. The period at which the eye is sensitive corresponds to the time of synapse overproduction and loss in the visual cortex. Out of the initial mix of overlapping inputs, the neural connections that belong to the eye that sees normally tend to survive, while the connections that belong to the abnormal eye wither away.
When both eyes see normally, each eye loses some of the overlapping connections, but both keep a normal number. In the case of deprivation from birth, one eye completely takes over. The later the deprivation occurs after birth, the less effect it has. By about 6 months of age, closing one eye for weeks on end will produce no effect whatsoever.
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The critical period has passed; the connections have already sorted themselves out, and the overlapping connections have been eliminated. This anomaly has helped scientists gain insights into normal visual development. By overproducing synapses then selecting the right connections, the brain develops an organized wring diagram that functions optimally. The brain development process actually uses visual information entering from outside to become more precisely organized than it could with intrinsic molecular mechanisms alone. This external information is even more important for later cognitive development.
The more a person interacts with the world, the more a person needs information from the world incorporated into the brain structures. Synapse overproduction and selection may progress at different rates in different parts of the brain Huttenlocher and Dabholkar, In the primary visual cortex, a peak in synapse density occurs relatively quickly. In the medial frontal cortex, a region clearly associated with higher cognitive functions, the process is more protracted: synapse production starts before birth and synapse density continues to increase until 5 or 6 years of age.
The selection process, which corresponds conceptually to the main organization of patterns, continues during the next 4—5 years and ends around early adolescence. This lack of synchrony among cortical regions may also occur upon individual cortical neurons where different inputs may mature at different rates see Juraska, , on animal studies. After the cycle of synapse overproduction and selection has run its course, additional changes occur in the brain.
They appear to include both the modification of existing synapses and the addition of entirely new synapses to the brain. Research evidence described in the next section suggests that activity in the nervous system associated with learning experiences somehow causes nerve cells to create new synapses. Unlike the process of synapse overproduction and loss, synapse addition and modification are lifelong processes, driven by experience.
This process is probably not the only way that information is stored in the brain, but it is a very important way that provides insight into how people learn. Alterations in the brain that occur during learning seem to make the nerve cells more efficient or powerful. Animals raised in complex environments have a greater volume of capillaries per nerve cell—and therefore a greater supply of blood to the brain—than the caged animals, regardless of whether the caged animal lived alone or with companions Black et al.
Capillaries are the tiny blood vessels that supply oxygen and other nutrients to the brain. In this way experience increases the overall quality. Using astrocytes cells that support neuron functioning by providing nutrients and removing waste as the index, there are higher amounts of astrocyte per neuron in the complex-environment animals than in the caged groups.
Overall, these studies depict an orchestrated pattern of increased capacity in the brain that depends on experience. Other studies of animals show other changes in the brain through learning; see Box 5. The weight and thickness of the cerebral cortex can be measurably altered in rats that are reared from weaning, or placed as adults, in a large cage enriched by the presence both of a changing set of objects for play and exploration and of other rats to induce play and exploration Rosenzweig and Bennett, These animals also perform better on a variety of problem-solving tasks than rats reared in standard laboratory cages.
Interestingly, both the interactive presence of a social group and direct physical contact with the environment are important factors: animals placed in the enriched environment alone showed relatively little benefit; neither did animals placed in small cages within the larger environment Ferchmin et al. Thus, the gross structure of the cerebral cortex was altered both by exposure to opportunities for learning and by learning in a social context. Are the changes in the brain due to actual learning or to variations in aggregate levels of neural activity?
Animals in a complex environment not only learn from experiences, but they also run, play, and exercise, which activates the brain. The question is whether activation alone can produce brain changes without the subjects actually learning anything, just as activation of muscles by exercise can cause them to grow. To answer this question, a group of animals that learned challenging motor skills but had relatively little brain activity was compared with groups that had high levels of brain activity but did relatively little learning Black et al.
There were four groups in all. What happened to the volume of blood vessels and number of synapses per neuron in the rats? Both the mandatory exercisers and the voluntary exercisers showed higher densities of blood vessels than either the cage potato rats or the acrobats, who learned skills that did not involve significant. How do rats learn?
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The objects are changed and rearranged each day, and during the changing time, the animals are put in yet another environment with another set of objects. These two settings can help determine how experience affects the development of the normal brain and normal cognitive structures, and one can also see what happens when animals are deprived of critical experiences.
After living in the complex or impoverished environments for a period from weaning to rat adolescence, the two groups of animals were subjected to a learning experience. The rats that had grown up in the complex environment made fewer errors at the outset than the other rats; they also learned more quickly not to make any errors at all. In this sense, they were smarter than their more deprived counterparts.
And with positive rewards, they performed better on complex tasks than the animals raised in individual cages. It is clear that when animals learn, they add new connections to the wiring of their brains—a phenomenon not limited to early development see, e. But when the number of synapses per nerve cell was measured, the acrobats were the standout group.
Learning adds synapses; exercise does not. Thus, different kinds of experience condition the brain in different ways. Synapse formation and blood vessel formation vascularization are two important forms of brain adaptation, but they are driven by different physiological mechanisms and by different behavioral events. Learning specific tasks brings about localized changes in the areas of the brain appropriate to the task.
For example, when young adult animals were. When they learned the maze with one eye blocked with an opaque contact lens, only the brain regions connected to the open eye were altered Chang and Greenough, When they learned a set of complex motor skills, structural changes occurred in the motor region of the cerebral cortex and in the cerebellum, a hindbrain structure that coordinates motor activity Black et al.
These changes in brain structure underlie changes in the functional organization of the brain. That is, learning imposes new patterns of organization on the brain, and this phenomenon has been confirmed by electro-physiological recordings of the activity of nerve cells Beaulieu and Cynader, Studies of brain development provide a model of the learning process at a cellular level: the changes first observed in rats have also proved to be true in mice, cats, monkeys, and birds, and they almost certainly occur in humans. Clearly, the brain can store information, but what kinds of information?
The neuroscientist does not address these questions. Answering them is the job of cognitive scientists, education researchers, and others who study the effects of experiences on human behavior and human potential. Several examples illustrate how instruction in specific kinds of information can influence natural development processes. This section discusses a case involving language development. Brain development is often timed to take advantage of particular experiences, such that information from the environment helps to organize the brain.
The development of language in humans is an example of a natural process that is guided by a timetable with certain limiting conditions. A phoneme is defined as the smallest meaningful unit of speech sound. Add to this the cultural emphasis that there is something dehumanizing in the discipline and moral restraints God imposes on us. Thus, to stand with God is often to stand against men and to face the fiery trials that go with Christian convictions. The Christian lives under the sovereignty of God, who alone may claim lordship over us.
Christian ethics is theocentric as opposed to secular or philosophical ethics, which tend to be anthropocentric. For the humanist, man is the norm, the ultimate standard of behavior. Christians, however, assert that God is the center of all things and that His character is the absolute standard by which questions of right and wrong are determined.
God has the right to issue commands, to impose obligations, and to bind the consciences of men. It is the creature's declaration of independence from his Creator. The change has much to do with our understanding of autonomy. Modern man considers the quest for autonomy to be a noble and virtuous declaration of human creativity. From the Christian vantage point, however, the quest for autonomy represents the essence of evil, as it contains within its agenda the assassination of God.
Used by permission. All rights reserved. Used by permission of Zondervan. You shall have no other gods before me. You shall not. We see that this is not law for law's sake, but for people's sake. That's where the "ethical theories" come in. A theory underlies our every moral action. We may not be able to articulate that theory or even be immediately conscious of it, but nothing manifests our value systems more sharply than our actions.
We view the world as fallen; an analysis of fallen human behavior describes what is normal to the abnormal situation of human corruption. God calls us out of the indicative by His imperative. Ours is a call to nonconformity-to a transforming ethic that shatters the status quo. Even secular writers and thinkers are calling for some sort of basic agreement on ethical behavior. Our survival is at stake. The thawing of the Cold War provided little comfort. Numerous nations have nuclear arms now or are close to having them. Not only is God concerned with justice, He assumes the role of judge over us.
It is axiomatic to Christianity that our actions will be judged. This theme is conspicuously absent in much Christian teaching today, yet it fills the New Testament and touches virtually every sermon of Jesus of Nazareth. We will be called into account for every idle word we speak. On the final day, it will not be our consciences that will accuse or excuse us, but God Himself.