Learning

 The human ability to gather, interpret, and remember aspects of the reality in which they find themselves immersed, and of which they are a part, is key to the survival of both individual humans and the species itself. The acquisition of knowledge includes not only the gathering of facts but also the acquisition of skills necessary for the acquisition of more facts and the performance of tasks which call for the use of these facts. In general terms, the more information a human possesses, and the more skills that human commands, the greater the likelihood of survival and the possibility of reproductive success. The possession of facts and skills allows for an emergent phenomenon to manifest itself in a human mind: a concept of the world and a (partial) understanding of the processes by which it works. The growth of a human’s knowledge and skills base is the general definition of the term learning. The ability of a human to bring this knowledge and these skills to bear in given situations is of crucial importance to that human’s general well-being. As we will soon see, learning involves physical alterations of the brain itself. These alterations manifest themselves as changes in the density of connections between neurons and the establishment of new neuronal pathways, pathways which facilitate the recall of learned knowledge and methods of applying it in real-life situations. Memory and learning are therefore closely connected.

 The Physiology of Learning

 As we have already noted, learning is intimately connected to memory. It is ultimately another example of neuroplasticity, the brain’s ability to physically modify itself. We should note that a full picture of how the brain’s neurons are modified by memory and learning (two of the foundations of cognition) is still being pieced together. Remarkable progress has nonetheless been made in this area in recent times. Technological advances have greatly facilitated this progress. The aim of this research is to understand how patterns of neuronal excitation and inhibition (what neuroscientists refer to as the E:I balance), in combination with patterns of gene expression, cause neuroplasticity to occur. It should be said that inhibition comes from a variety of sources and this has an effect on particular circuits.¹

 The fundamental principle, as we have seen in our examinations of consciousness and memory, is that experience has the ability to cause physical alterations within the brain’s neural circuitry. What is the process by which this happens? First, there must be some form of stimulus that reaches an individual’s senses. As we have seen, this stimulus is converted by the process of sensory transduction into electrical impulses which are then processed in the brain’s association areas. We briefly touched on Associative Memory in the chapter on memory. Now, we will look at those regions of the brain that neuroscientists call the association areas. We looked at these in a general way in our brief introduction to cognition. Now, we will examine their more specific components. Some of these areas are involved with the relationship between stimulus and motor response. Others are primarily oriented toward the processing of language and other symbolic forms of communication.

 Two specialists in brain research characterize the association area in the following manner:

 …higher-order association cortex is characterized by connectivity to association zones located in widely distributed positions throughout the cortex. Association regions in one zone of cortex (e.g. the inferior parietal lobule) will receive and send projections to zones of temporal, prefrontal, and midline association cortex.²

 In effect, the association areas of the brain form a network. As we have already seen, the formation of neural networks among and between cortical areas is a fundamental feature of the human brain. Two Harvard neuroscientists have hypothesized that during the evolution of the brain, the expansion of the association cortex “may have allowed for an archetype distributed network to fractionate into multiple specialized networks.” It is these specialized networks, they contend, that support the various higher order cognitive processes, including language.³

 A neuroscientist studying learning has identified these brain structures as part of the association regions: the medial temporal lobe (especially the hippocampus), motor regions of the frontal lobe (which are crucial in associating visual stimulus with motor response), the prefrontal cortex (also involved in linking visual stimulus to response), and the striatum.⁴ A pair of neuroscientists at Yale describe the striatum as follows:

 The striatum is a critical component of the brain that controls motor, reward, and executive function. This ancient and phylogenetically-conserved structure forms a central hub where rapid instinctive, reflexive movements and behaviors in response to sensory stimulation or the retrieval of emotional memory intersect with slower planned motor movements and rational behaviors…The convergence of excitatory glutamatergic activity from the thalamus and cortex, along with dopamine release in response to novel stimulation, provide the basis for motor learning, reward seeking, and habit formation.⁵

 In regard to those regions of the cortex involved in learning and using language, physiologists have identified regions of the brain’s left hemisphere involved in these processes.

 From different overviews…it is clear that the language-relevant cortex includes Broca's area in the inferior frontal gyrus (IFG), Wernicke's area in the superior temporal gyrus (STG), as well as parts of the middle temporal gyrus (MTG) and the inferior parietal and angular gyrus in the parietal lobe. Within these macroanatomically defined regions, microanatomical subregions can be specified.⁶

More broadly, the physiology of the brain’s language centers allows for language acquisition, the learning of a language. We will examine these structures more closely in the chapter Speech and the Evolution of Language.

As we noted in this chapter’s introduction, learning causes changes in neural interconnectedness. Now we will focus more intently on the processes by which this occurs. We should emphasize that in learning it is the synapse itself that is being strengthened. A psychology professor and brain researcher has explained the phenomenon as follows:

The connections between neurons, through the synapses, however, are constantly changing throughout all of our life and are predominantly responsible for learning and memory in the brain. These changes in connections involve forming new connections, known as synaptogenesis, or strengthening existing connections, known as long-term potentiation (LTP)…

The researcher goes on to say that in laboratory experiments with rats, the rats’ synapses can form “more extensive interconnections between their neurons…with a greater number of synapses” when the rats are given suitable stimulation.⁷

Further, he points to a critical fact: when multiple neurons respond to a stimulus at the same time, the connections between them are strengthened, a hypothesis first proposed by the Canadian psychologist Donald Hebb.

 …Hebb described an important process for learning in the brain, known as Hebbian learning (1949), summed up by the phrase, “neurons that fire together wire together...”Put simply, when two or more neurons respond or fire at the same time (i.e., from some thought, action, or event in the environment) the connection or synapse between them is strengthened, leading to a stronger association. This means that if some situation (or thought or action) is encountered in the future causing one of those neurons to respond, it will now be more likely to trigger a response in the other connected neurons, recalling and further reinforcing that association.⁸

What are the mechanisms of neuroplasticity? Neurogenesis, as we noted above, apoptosis, or programmed cell death, (which we encountered in Volume One), and degrees of synaptic change caused by activity or non-activity. To quote one brain researcher, “Repetitive stimulation of synapses can cause long‐term potentiation or long‐term depression of neurotransmission.” These changes can cause physical alterations in dendritic spines. They can also alter neuronal circuits, and with them, behavior. These processes appear to have a major impact on the brain’s ability to acquire new information, react to quickly changing external circumstances, or recover from injury.⁹

We noted above that gene expression is a factor in neuroplasticity. Specifically, what that means is that there is a reciprocal relationship between synaptogenesis and a person’s genes. Gene mutations can cause errors in synaptic formation. These synaptic errors can in turn hinder neurodevelopment and damage the brain’s normal functions, sometimes very seriously so.¹⁰ In turn, synaptic formations can affect the expression of genes. As one study puts it, “…studies indicate that neuronal activity regulates a complex program of gene expression involved in many aspects of neuronal development.”¹¹

In addition to Hebbian learning, researchers also investigate synaptic scaling. Synaptic scaling refers to the ability of a neuron’s synapses to adjust their rate of firing in order to maintain their homeostatic equilibrium. Research has shown that neurons use calcium-dependent sensors to detect fluctuations in their firing rates. These sensors then allow greater or lesser accumulations of receptors for glutamate (the chief excitatory neurotransmitter) in the synapse.¹² Synaptic scaling seems to be crucial for the storage of associative memories, specifically, the ability of a person to remember important aspects and details of particular events.¹³

In humans there is, of course a relationship between learning and development, a relationship that sheds light on neural plasticity. The human brain has mechanisms that deal with experience-expectant plasticity [neuronal development based on common or nearly universal experiences such as exposure to language], and experience-dependent plasticity [neuronal development specific to the experiences of an individual, development which facilitates the ability to learn throughout life, and development that strengthens or eliminates neural connections]. The two forms of plasticity are deeply intertwined and both influence each other. Experience-dependent plasticity tends to be greater in children than adults, but plasticity in adults takes place in a different context. As one researcher has put it,  

…modifying synapses that are already committed (e.g. learning a motor skill such as juggling) is very different than committing the synapse for the first time (e.g. learning the motor coordination necessary for the first time a baby holds himself up).¹⁴

Researchers are also exploring the structure of the neocortex itself to gain insight into the learning process. One team of researchers, noting the hierarchical arrangement of the regions of the neocortex and the arrangement of cortical neurons into columns, has proposed a hypothesis about how the brain learns to recognize objects. In their words,

We believe each cortical column learns a model of “its” world, of what it can sense. A single column learns the structure of many objects and the behaviors that can be applied to those objects. Through intra-laminar [within layers] and long-range cortical-cortical connections, columns that are sensing the same object can resolve ambiguity.¹⁵

So the sensory stimulus that begins the processes of learning undergoes complex processing in the brain. This processing physically transforms the brain itself. From this, a synergy arises. The more the brain’s synapses are strengthened and the more neuronal circuitry is expanded, the greater the ability of the brain to absorb additional learning, which in turn will cause new waves of synaptic transformation.

Forms of Learning

What are the general ways in which humans learn? Perhaps the most basic one is imitation. How might imitation be defined? One team of researchers has put it this way:

…we use the broadest and simplest definition of imitation as follows—we call an action imitation if there is a relationship between the behaviour of a copier and a model, such that observing the movements of the model causes the parts of the copier's body to move in the same way relative to one another as the parts of the model's body…

In their description of it, imitative behavior is variable. People can use various parts of their body to imitate, such as their hands and faces. They can also imitate using their voices. Their imitations vary in accuracy and can be imitations of things which are new to them or familiar in varying degrees. Imitations can be conscious actions, or they can be spontaneous. And the result of these imitations is unpredictable.¹⁶

In the study of imitation, a major debate is over the issue of when children begin to imitate the actions of others. One researcher in the field of early childhood development contends that no genuine imitation occurs in humans until early in their second year, and that claims of newborns engaging in imitation rest on preformationism, “the view that development is the growth of pre-formed complex structures”. She finds no convincing evidence to support preformationist ideas, and contends that:

…imitation will be the emergent, stable product of the coming together of a range of distinct kinds of knowledge and skill. Such multi-component systems are not deterministic and do not follow a built-in blueprint for the development of behaviours. They are self-organizing and can generate new behaviours through their own activity.¹⁷

And a team of experts in the study of child psychology finds that toddlers can use imitation to communicate with others and are can take steps to ensure others see their imitation.¹⁸

It goes without saying that the ability to imitate is deeply ingrained in the human brain. Brain researchers have identified specific regions of the brain that facilitate imitation.

[The] Human ability to imitate movements is instantiated in parietal, premotor and opercular structures, often referred to as the human homologue of the macaque mirror neuron system…Critically, the activity of the parietal opercula bilaterally was associated with the anatomical compatibility effect. [NB: The anatomical compatibility effect is when a physical response to an observed phenomenon appears to be the most appropriate one, a response that increases with repetition.]  Furthermore, increased activity of the left middle frontal gyrus and right superior temporal sulcus (extending to the temporo-parietal junction) was found in those trials in which the spatial mapping between the seen and executed movements was detrimental for the anatomical task.¹⁹ 

Imitation plays a crucial role in language acquisition, as we will see in detail later. And in general imitation is so pervasive in the human experience that it may be the origin of human communication itself, a topic we will examine in a subsequent chapter.

Humans can also learn by means of conditioning. By conditioning we mean, in its most basic sense, a learned response to a given stimulus. Classical conditioning, also known as associative learning, means getting a subject to give a particular response to a neutral stimulus.  Operant conditioning is getting a subject to associate a given behavior with a specific consequence, either a reward or a punishment of some sort. Rewards naturally tend to increase the behaviors that result in them and punishments tend to decrease behaviors. These rewards or punishments are sometimes referred to as positive or negative reinforcement.

As is the case with imitation, conditioning is a pervasive feature of human life. (Operant conditioning governs much of child raising, for example.) One needn’t fall into the error of thinking that operant conditioning is the only factor that governs human behavior to see that in many cases it influences such behavior. But this influence always falls within a larger cognitive and experiential context.

In a later volume of this work, we will examine how the educational systems in human societies evolved and the methods by which they have attempted to build on the basic foundations of human learning.

The Relation Between Innate Behaviors and Learned Behaviors

There is a distinction between behaviors which require no learning process and those that do. Behaviors that require no learning are called innate. These are genetically-determined behaviors, such as reflexes or other bodily reactions to stimuli. Innate and learned behaviors are usually considered to be distinct, but in recent years many researchers have come to see them as deeply intertwined. There is evidence that certain neural circuits once considered to be innate demonstrate plasticity. It now seems certain that all complex behaviors are a synthesis of innate and learned behaviors, which shape each other in a synergistic fashion.²⁰ We will examine the relationship between genetic predisposition and experience in greater detail in a subsequent chapter.

It is sobering to remember that a great deal of what humans learn is utterly wrong. Humans learn “facts” (such as the belief that there was an actual Noah’s Ark) that bear no relationship to reality. They also learn prejudices. They learn ways to harm others. They learn bad habits and self-destructive behavior. My point is that learning is not always a benign thing, although in fact the vast majority of what humans learn is quite ordinary and mundane. But at its best learning exalts a human being, opening up realms of knowledge that transform them for the better, broaden their outlook on life and the world, give them skills which will prepare them for a variety of tasks, and help them to understand at least something about their place in reality. The learning process is vastly influenced by an individual’s intelligence. It is to the definition and nature of intelligence that we now turn, seeking in them clues to our success as a species. More darkly, we will see how the possession of intelligence is a two-edged sword, enabling us to dominate the world while at the same time giving us the power to destroy it.

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