The Making of the Mind: The Neuroscience of Human Nature (17 page)

By late childhood, our natural inclination to see ourselves as heroes destined to success has abated to a degree, but it never leaves us completely, even as adults. Part and parcel of the positive illusions of even adult thought is a conviction that we can control events to a far greater extent than is actually possible and that we will steer outcomes toward positive rather than negative outcomes. For example, most adults believe that they are less likely than others to be involved in a car accident because they believe that they possess above average driving skills. Obviously, we cannot all be above average, but this is what the psychologist must conclude from listening to the interpreter of each individual mind telling the story. Some people prefer the risk of driving a car on a long trip rather than flying on a commercial aircraft because they believe in their ability to prevent an accident through personal control. The
reality is that traffic fatalities are far more common than commercial aircraft fatalities, from the massive numbers of cars on the road alone, and bad things can happen that are beyond personal control.

Maintaining a positive illusion of control can be thought of as highly adaptive in coping with inherently risky situations.
³³
In the absence of convenient mass transit in some places in the industrialized world, driving a car is often the only realistic transportation option for trips too far to walk or bicycle. Believing that you are in control as the driver puts fear to the side and lets you get on with your life. Without this illusion of control, the alternative might be fear and paralysis.

In other cases of risk, however, illusions of personal control are less helpful. Take, for instance, a belief sometimes held by heavy gamblers that they can exert some influence over the roll of the dice, the fall of the roulette wheel, or the card turned up next in blackjack or poker. The craps shooter blowing on the dice, putting some body English into the throw, or getting the dice first kissed for good luck illustrates the underlying hope that control over chance is possible. Fortunes have been lost on such illusions.

One of the best illustrations of the interpreter's built-in positive bias can be seen in the way we think about the future. Again, assuming that the brain is fully healthy and not suffering from depression, the future constructed by the interpreter is generally bright. We carry with us a positive illusion of optimism.
³⁴
Some of us are more optimistic than are others, but, taken as a whole, the human species thinks, quite irrationally, that the future is likely to be better than the present and certainly better than the past. Instead of using our past and present happiness and circumstances as realistic predictors of the future, the mind's interpreter does quite the opposite. This healthy illusion of unwarranted optimism is not seen in depressed people. In fact, the pessimism of depression is one of the cardinal symptoms of the disease. Usually mental illness involves losing contact with reality, but here, oddly, the depressed person may be more in touch with reality than the healthy optimist.
³⁵

It is important to clarify that positive illusions differ from the Freudian psychological mechanisms of self-defense known as repression and denial.
³⁶
Repression forces anxiety-provoking thoughts out of the focus of attention. It protects the self, or what Freud called the ego, by keeping disturbing thoughts
out of consciousness. In repression, a disturbing reality (e.g., witnessing or hearing of the death of a close friend or relative) is recognized and accepted but kept outside of conscious awareness as a means of self-protection. With denial, the disturbing reality is not accepted in the first place—the interpreter avoids harm to the self by refusing to acknowledge the death, explaining it all as a mix-up in communications or a case of mistaken identity. Thus, both repression and denial are psychic means of distorting reality in important ways. Positive illusions, on the other hand, are merely favorable interpretations of reality. They do not alter reality; they merely cast reality in the best possible light, one in which the self is in control and the future looks bright.

What happens to the self if the brain suddenly loses its interpretive capacity and inner voice? A remarkable portrait of exactly this situation comes from Jill Bolte Taylor, a neuroscientist who suffered and survived a major stroke. After suffering a massive hemorrhagic stroke in her left hemisphere, she eventually, after six years of heroic rehabilitation, recovered and went on to lecture and write about the day it happened. As a neuroscientist, she was able to describe with clarity and accuracy the experience of losing the critical regions of the left cerebral hemisphere that support causal inference, working memory, and language. When these became dysfunctional, her inner voice fell silent, stopping the familiar self-narrative that normally accompanies every moment of wakeful consciousness. What remained was a state of awareness mediated by her fully intact right hemisphere. She described the experience in her book
My Stroke of Insight
:

I existed in some remote space that seemed to be far away from my normal information processing, and it was clear that the “I” whom I had grown up to be had not survived this neurological catastrophe. I understood that that Dr. Jill Bolte Taylor died that morning, and yet, with that said, who was left?…Without the language center telling me: “I am Dr. Jill Bolte Taylor. I am a neuroanatomist. I live at this address and can be reached at this phone number,” I felt no obligation to be her anymore…. I stopped thinking in language and shifted to taking new pictures of what was going on in the present moment. I was not capable of deliberating about past or future-related ideas because those cells were incapacitated. All I could perceive was right here, right now, and it was beautiful.
³⁷

The left-hemisphere interpreter, then, is crucial to our inner sense of self. The interpreter shapes the memories of who we have been and who we will become, inscribing our autobiography in the pages of long-term memory. But how is it possible for the interpreter to travel back into the past and forward into the future? Just what is this remarkable ability made possible through what cognitive neuroscientists call episodic memory?

In 1985, Michael J. Fox traveled backward in time to 1955 as the character Marty McFly in the movie
Back to the Future
. There Marty met his teenage mother, who at the time of his teleportation backward in time did not think much of his nerdy father, who was the laughingstock of the high school. Marty managed his miraculous time travel thanks to Doc, the mad scientist who invented the “flux capacitor” and mounted it on the dashboard of a DeLorean sports car. As Marty discovered, there were both ups and downs to traveling through time. What would happen, for example, if his then teenage mother developed a crush on Marty—her future son—and steered clear of his father completely? Would Marty simply disappear from existence, erased from history by a logical conundrum in the space-time continuum? Time travel, not surprisingly, is a staple of science-fiction literature, going back to H. G. Wells's classic
The Time Machine
in the late nineteenth century.

No less remarkable, or hazardous, is the human capacity for
mental
time travel. The mind can go back in time to relive past experiences or move forward in time to imagine future events. The cognitive system responsible for this mental version of time travel is called episodic memory. It is different from semantic memory in that the time and place of the experience is part of the memory. Its most unique feature is the capacity to turn back the arrow of time in the sense that the one doing the remembering is traveling backward into her past. Endel Tulving, who first defined and pioneered the study of episodic memory, articulated the marvel of this feat of the human mind:

With one singular exception, time's arrow is straight. Unidirectionality of time is one of nature's most fundamental laws…. The singular exception is provided by the human ability to remember past happenings. When one thinks today about what one did yesterday, time's arrow is bent into a loop. The rememberer has mentally traveled back into her past and thus violated the law of the irreversibility of the flow of time. She has not accomplished the feat in physical reality, of course, but rather in the reality of the mind, which, as everyone knows, is at least as important for human beings as is the physical reality.
¹

The capacity of episodic memory is crucially linked to the ability to travel forward in time as well as to travel backward. That is to say, one is able to imagine an experience in the future using the same brain/mind system responsible for remembering past experiences. To appreciate this point, it is important to understand that retrieval of the past event from long-term memory is not like retrieving a book from a library or a file from a computer disk. Instead, retrieval is an act of reconstructing the past experience and using one's creative capacities to fill in the gaps as needed. Reconstruction of the past is in principle really no different than constructing a future scenario. In practice, the past provides more guidance as to what fits in the reconstruction and what does not. Also, for most of us, the future is too much of a blank canvas and so we sketch in the outlines of a future scenario by recollecting a relevant past episode as the point of departure.

Long-term memory is a complex system that is organized hierarchically. At the top of the hierarchy, cognitive psychologists contrast declarative memory—storage of what X is—with nondeclarative or procedural memory—storage of how to do X.
²
Declarative memory divides into two distinct branches, episodic memory and semantic memory. The episodic part holds memories of specific past events and experiences while the semantic part is a storehouse of all our conceptual and factual knowledge. The semantic component of long-term memory allows one to know things about the world without remembering exactly how this knowledge was obtained. Semantic memory makes no reference to specific episodes situated in space and time. For example, suppose you spot a red sports car on the street. Recognizing the object as a car draws on semantic memory—your knowledge of the concept
of cars, the superordinate concept of vehicles, and the subordinate concept of sports cars. Such memory allows you to list the properties of sports cars that distinguish them from other kinds of cars. It enables you to know that red is only one possible color for the car, and a rather dashing one at that. By contrast, if the sports car is one you have seen in the past—at a specific time and place—then that recollection is dependent on episodic memory. What, when, and where you experienced the object or event in the past is an inherent aspect of the memory. To take a different example, knowing what a birthday party is depends on semantic memory; recollecting your tenth birthday party requires episodic memory. In the laboratory, human beings routinely are able to distinguish between what they know to be true about information presented earlier in the experiment and the mental experience of traveling back in time and remembering its occurrence.

The two aspects of declarative memory are independent of each other, as dramatically revealed by the case of a patient identified by his initials, H. M. To control his severe epileptic seizures, surgeons removed most of his hippocampus from the limbic system on both the left and right side, along with some surrounding tissues in the temporal lobe, including the amygdala. The operation was a success from the standpoint of the seizures, but medicine was unaware at the time of the critical role that these brain regions play in episodic memory. It was discovered soon after the surgery that the procedure had resulted in a severe impairment of memory.

H. M.'s intelligence was not generally impaired by the surgery, which left his semantic store of concepts and facts about the world intact.
³
In fact, because the surgery successfully reduced the frequency of his epileptic seizures, his IQ score actually improved somewhat following the operation. However, it caused a profound case of anterograde amnesia that prevented H. M. from being able to store new experiences in long-term memory. This meant that H. M. could not remember events that had occurred a few minutes earlier. Once an experience faded from working memory, H. M. was unable to store and later retrieve that information on a more permanent basis in long-term memory. Thus, he lost the ability to store new events in episodic memory even though his semantic memory remained intact.

Although H. M. could not store new events in episodic memory, the
autobiographical details of his preceding the surgery had already been stored successfully—these memories were not forgotten. He could easily tell stories about his days as a school boy, for example. Also not impaired were his semantic knowledge of concepts and his procedural memories for how to do things. He continued to mow the lawn as a household chore, to work jigsaw puzzles, and to read magazines. However, he had to be told “where to find the lawnmower, even when he ha[d] been using it only the day before.” And he would “read the same magazines over and over again without ever finding their contents familiar.”
⁴
Similarly, he could not remember the names of people whom he had met since the operation. Nor could he remember the location or address of a home he had moved into after the surgery. Instead, left on his own, H. M. would return to his old address a few blocks from the new one.

Another amnesia case important to understanding episodic memory is that of K. C., who suffered serious head injuries in a motorcycle accident that damaged many brain regions, including the inner or medial temporal lobes.
⁵
Tests on K. C. revealed normal intellectual skills. His working memory was also fully intact, meaning that he could remember new information for brief periods of time. There were no problems with his ability to read or to write, his ability to think clearly, or his ability to display previously learned skills such as playing the organ or chess. He could recall the facts of his life, such as his date of birth or the names of schools, but he was able to do so because they were objective facts stored in his semantic memory system. Similar to H. M., he suffered from a serious anterograde amnesia involving a deficit in storing new personal experiences, but at the same time K. C. exhibited a unique form of retrograde amnesia that was restricted to autobiographical experiences from the past that preceded his accident. K. C. was unable to remember any specific episodes even though he could remember factual information. That is to say, he could not travel back in time and recollect any particular personal experiences situated at a specific time and place, even when given various reminders about particular events. He denied any recollection or even any sense of familiarity with the particular event.

Thus, the consciousness of K. C. was cut off from the autobiographical past that human beings normally access through mental time travel. Although concepts and facts—the contents of semantic memory—were fully intact, he
had lost access to an episodic-memory store that held the events of the past in relation to the self. Of equal importance and great significance, this absence of past memories was accompanied by an inability to imagine the future. “When asked, {K. C.} cannot tell the questioner what he is going to do later that day, or the day after, or at any time in the rest of his life. He cannot imagine his future any more than he can remember his past.”
⁶

It is difficult to say for certain, but it appears unlikely that nonhuman primates are capable of episodic recollection. Apes, and mammals in general, clearly are able to store knowledge about the world and use the hippocampus in learning new information. A vast scientific literature demonstrates clearly that the medial temporal lobe of the primate brain is critical to declarative memory. However, memory for factual information about the world is not the same as memory for specific events. As Endel Tulving has noted, “The kinds of tasks that have been used in evaluations of the hippocampal declarative memory system do not, and cannot, distinguish between memory for events and memory for facts.”
⁷
Just as young children are able to learn facts without any difficulty before they begin to recollect specific autobiographical events from their personal past, apes may be fully capable of using semantic memory without any episodic memory. An ape may be fully capable of learning X but not have a recollection of when X was learned; the subjective experience of learning X, situated in the past, may be missing in all but human beings.

The thrust of most tests designed to assess animal memory makes use of where an event took place but rarely attempts to assess when the event occurred. The spatial but not the temporal aspect of episodic memory is typically addressed. Indeed, the essential feature of episodic memory is the subjective experience of mentally traveling backward or forward in time. Because the experience of another organism cannot be directly measured, and because apes cannot report their experience to us, this key aspect of time would seem to be outside the realm of investigation.
⁸

One of the best attempts to demonstrate that nonhuman primates have at least the rudiments of episodic memory involved testing a lowland gorilla named King.
⁹
The gorilla was given food, such as an apple, at Time 1. Either five minutes later or as long as twenty-four hours later, King was rewarded for making a response that correctly identified what food he had been given
earlier and who had given it to him. King was better at correctly identifying who gave the food than he was at identifying what the food was, but both dimensions were well above chance performance even after a twenty-four-hour retention interval. As the investigator pointed out, however, it is possible that King simply learned to store “the facts” of what was eaten and who provided the food in order to get a reward five minutes or twenty-four hours later. King was tested repeatedly in this setting, and he knew the test and the possibility of a reward would be forthcoming. It is also possible that King relied on the familiarity of “knowing” the correct food and provider without having a mental experience of remembering when the information was learned. The temporal dimension, especially the subjective experience of mentally traveling backward in time, cannot be readily assessed.

What is known for certain is that human beings are highly skilled mental time travelers. Our ability to think about the future may in fact be a crucial contribution to cultural evolution. Having an awareness of the future may be partly responsible for the human drive to innovate new and better ways of doing things—it is not just for us but also for the benefit of future generations. In other words, mental time travel may interact with our advanced executive function that enables planning and our advanced social intelligence that enables cooperation. Without an awareness of the future, nonhuman primates may “not initiate and persist in carrying out activities whose beneficial consequences will become apparent only in the future, at a time that does not yet exist.”
¹⁰

RECONSTRUCTIVE RETRIEVAL