The Making of the Mind: The Neuroscience of Human Nature (5 page)

In chapters
7
and
8
, it is shown how the five parts of the ensemble hypothesis are revealed in human emotion and our readings of the minds of other people in social relationships. Both emotion and a social nature are, of course, found in all primates, and in mammals more generally. Yet it is contended here that human emotion and the human social mind are thoroughly colored by the modern mental ensemble. At the pinnacle of human mental functioning perhaps are our capacities for morality and spirituality. These, it is argued in chapters
9
and
10
, are again largely, if not entirely, products of the ensemble.

Finally, how is the human mind changing in the twenty-first century? Despite that it is biologically the same as it was forty thousand years ago, cultural evolution has dramatically altered the way the modern mind functions. As argued in
chapter 11
, the emergence of the literate mind through the invention and multiple uses of writing must be seen as a product of the modern mental ensemble. The ways literacy altered human cognition over the past few thousand years of history were enabled by specific parts of the ensemble. Today we find ourselves both exhilarated by and drowning in the information overload of the telecommunications and computer revolution of the late twentieth century. Just as the ensemble produced a literate mind
from the invention of writing, so, too, will it shape a postliterate, Internet mind from today's cognitive technologies. The book closes, then, with a look toward where our capacities to plan, to collaborate, to write, to interpret, and to imagine might someday take us.

The human mind is highly adept at executive functioning—the ability to make decisions and manage other cognitive processes. Our ability to plan solutions to novel problems—as we have been doing as a species since the dawn of humanity in the Upper Paleolithic—is a common indicator of executive function. Another is the ability to delay immediate gratification to obtain a more valuable reward later (e.g., work hard now in order to get paid at the end of the week). A third example is the ability to inhibit impulses that offer pleasure but conflict with other important personal goals (e.g., skip the donut with morning coffee to pursue a goal of losing weight). Executive function is known to require the successful maturation of the prefrontal cortex of the brain during infancy, childhood, adolescence, and even extending into young adulthood. This is because the prefrontal cortex includes a neural network serving executive attention and other components of working memory. This system of short-term memory enables the brain to retrieve mental representations from long-term storage and maintain them in an activated state. Our ability to think before we act depends on this transient form of memory. Facts and skills that have been learned and stored in long-term memory can be retained in an inactive state for hours, days, weeks, months, or years. By contrast, working memory stores information for only half a minute or so. If executive attention is focused on the words, images, and other thoughts, then these mental representations can be kept active for a few moments longer within our immediate conscious awareness. Without continued
attention, however, the contents of working memory dissipate rapidly and slip out of mind.

Try to multiply 8 × 14 without writing anything down. The numbers must be maintained in working memory and attention given to multiplying 8 × 4. By storing a 2 in the digit column and carrying a 3 in the tens column, one can then proceed with multiplying 8 × 1 and adding the carried 3. The correct answer will emerge from this mental work only if working memory can effectively deploy its capacity for attention and transient storage of mental representations. In a similar way, solving novel problems, delaying gratification, and inhibiting impulses require the effective deployment of executive attention and the short-term storage of working memory. Holding in mind alternative possible solution paths while problem solving, comparing the value of immediate to delayed rewards, and focusing on a long-term goal over immediate pleasure illustrate some of the reasons why this is so.

Because working memory is transient, its value in human cognition may be less apparent than the value of long-term memory, the repository of everything learned throughout a lifetime. It is obvious that human and nonhuman intelligence requires an ability to learn and retain things for many years. Yet bringing these things into awareness and holding them as long as they are needed is also essential. A leading researcher of the neural basis of working memory, P. S. Goldman-Rakic, explained its real value:

The brain's working memory function, i.e., the ability to bring to mind events in the absence of direct stimulation, may be its inherently most flexible mechanism and its evolutionarily most significant achievement. At the most elementary level, our basic conceptual ability to appreciate that an object exists when out of view depends on the capacity to keep events in mind beyond the direct experience of those events. For some organisms, including most humans under certain conditions, “out of sight” is equivalent to “out of mind.” However, working memory is generally available to provide the temporal and spatial continuity between our past experience and present actions.
¹

The flexibility in thought and behavior afforded by working memory led some scholars to wonder about its role in the great leap forward in tool
making and symbolic art associated with the origin of the modern human mind. Possibly a genetic mutation produced a reorganization of the brain compared with other members of the genus
Homo
that resulted in an advanced form of working memory. Consider that stone tools made by
Homo neanderthalensis
in the cave shelters of Europe included scrapers, sharp points, and tools with thin edges. The design of these tools represents the Mousterian style; it took considerable skill to craft the stone for the functions of scraping and sawing or to attach the sharp points to a spear for use in hunting. The Neanderthals were obviously capable of acquiring the expertise needed to make such tools and perhaps did so in the same way work skills are acquired still—through practice and apprenticeship with an expert craftsman. It seems likely that the knowledge and skills were passed on from one generation to the next by the young novice learning from the old master. However, it is curious that the stone tools of the Neanderthals did not appear to change and improve in design over the two-hundred-thousand-year-long history of the species.
²

Despite the impressive tool-making skills of the Neanderthals, archeologists have not detected signs of innovations over multiple generations, as is so characteristic of the cultural evolution of modern humans. Even from one generation to the next, our species may make improvements in the design of a tool or product and pass it on to the next generation to mull over and refine, such as innovations in the forms of wheeled transportation from the chariot to the contemporary car. Yet, for more than two hundred thousand years, Neanderthals appeared to make the same model of scrapers, for example. They continued to make, without tinkering or planning new designs, the same kind of stone-tipped spears for hunting. In the same vein, carved figurines and representational cave paintings of animals—both highly inventive and planning intensive—are associated only with modern humans.

To illustrate, consider a famous piece of representational art made by modern humans, the Hohlenstein-Stadel figurine.
³
It was discovered in southwestern Germany and dated as thirty to thirty-three thousand years old. The figurine, carved from ivory, represents the body of a man and the head of a lion. Such chimerical beasts have been part of the folklore, mythologies, and religious practices of modern humans from our origins in prehistoric times. The key point here is that to carve a chimera its creator needed to hold in
mind two different concepts at once and then combine some of the properties of a lion with some of the properties of a man. The visual and spatial representations of each concept had to be kept active in working memory, while executive attention was directed to the head of one and the body of the other. The fascinating art work of the Hohlenstein-Stadel figurine provides insight into the advanced working memory capacity of early modern human beings.
⁴
Gaining the power of an advanced system of working memory, then, could be the cognitive Rubicon crossed only by modern human beings in the course of hominid evolution.

Another clear example of the executive functioning of modern human beings is the use of lines of mounded stones as corrals for herding and then trapping gazelles. Evidence of such ancient hunting technology dates back only twelve thousand years or so, indicating they were the design of modern humans and required “the delayed gratification and remote planning in space and time that is typical of modern executive functions.”
⁵

Cognitive psychologists have developed and empirically tested detailed theories about the cognitive architecture of the modern human mind. These theories describe the basic functional systems of human cognition, such as the distinction between working memory and long-term memory. The objective of cognitive neuroscience is to map these functions onto the structures of the brain outlined in
chapter 1
. More precisely, the goal is to map particular functions, such as working memory, on specific neural networks that may be localized in multiple brain regions and structures. The nervous system, as well as the respiratory system and the cardiovascular system, are structured in a hierarchy of parts and subparts. For example, the nervous system consists of a peripheral branch and a central branch, which in turn breaks down into the spinal cord and the brain. The peripheral branch includes sensory and autonomic components. The latter in turn breaks down into the sympathetic and parasympathetic parts. In a similar way, the cognitive architecture must be understood in terms of a hierarchical structure.

An influential model of working memory was proposed by Alan Baddeley in his 1986 book titled
Working Memory.
It included two storage components—the phonological loop and the visuo-spatial sketchpad—and a central executive that supervised the contents of these stores through attention. That
is to say, executive attention retrieved information from long-term memory and manipulated it in one of the stores, such as occurs during mental arithmetic. The storage components are tailored to specific kinds of information. One type extensively investigated by cognitive psychologists is dedicated to the storage of verbal information in the form of the sound or phonology of words. Baddeley referred to it as the phonological loop to emphasize how verbal information can be recycled by silent mental repetition or rehearsal, as we might do with the name of a person to whom we were just introduced. By keeping the name active in verbal working memory, we can address the individual by name moments later. Besides words, visual-spatial representations can also be stored in working memory. It is this storage device that is called into service in the experience of visual imagery. Imagine the living room of your current residence. Such mental imagery can be maintained for several moments within the visuo-spatial sketchpad. This sketchpad actually consists of two independent stores, one for visual representations and another for spatial locations. Whereas the visual store makes use of neocortical regions in the left hemisphere, the spatial store depends on a neural network in the right hemisphere.
⁶

Long-term memory is also hierarchically organized. A major division separates declarative knowledge of facts, concepts, and specific events learned in the past from nondeclarative or procedural knowledge of skills and conditioned habits. It divides our “what” knowledge from our “how” knowledge. For example, long-term memory stores “what” a bicycle is separately from “how” we ride a bicycle. The “what” storage entails a concept of bicycles in general or perhaps a memory of an event with a specific bicycle (e.g., our childhood bicycle seen for the first time one Christmas morning). The “how” storage is very different. Instead of a verbal description or visual image, the procedures for riding a bicycle are remembered in the muscles and senses as a perceptual-motor skill. An amnesic patient might forget that he ever owned a bicycle, but he would still retain the skill of riding one because the two kinds of memory are stored independently of each other.

Another way to think about the organization of long-term memory cuts across the distinction between declarative and procedural storage. The domain of knowledge defines the organization rather than the difference
between “what” and “how.” Bicycles and all other inanimate objects made by human beings constitute a domain of knowledge that is stored separately from our knowledge about plants and animals as living things. Knowledge about people and social relationships is a third domain. Each of these domains includes declarative knowledge of facts, concepts, and specific events from the past as well as procedural knowledge. For instance, within the domain of knowledge about people, the brain can store the general concept of a human face, a multitude of facial images of specific people met in the past, and the perceptual skill of rapidly recognizing a face from all other objects or a specific face in a room crowded with many people.

Thus long-term memory is organized in terms of distinct domains of knowledge, and each domain is further broken down into specific modules. A module is a system, involving one or more regions of the cerebral cortex, that specializes in a particular domain of cognitive activity. The domain of knowledge about people includes multiple modules dedicated to specific tasks. The most extensively investigated is a perceptual module dedicated to the recognition of faces. Due to damage to the face recognition module, prosopagnosic patients are unable to recognize the faces of people—even the faces of those whom they know very well and can recognize from, say, their speech. Prosopagnosia involves regions lying at the juncture of the temporal and occipital lobes of the brain. The superior temporal sulcus and an area in the fusiform gyrus of the temporal lobe join forces with the inferior occipital cortex to process faces.
⁷
These neural regions in the right hemisphere are particularly sensitive to faces. Objects must possess the right features, such as hair, forehead, eyes, nose, mouth, and chin, and these features must be configured properly (e.g., nose above the mouth) to elicit a strong response from the right temporal-occipital network. Non-faces, such as inanimate objects like bicycles, are processed by separate neural networks in different, more anterior regions of the temporal lobe.