8. The Seven Sins: Vices or Virtues?

The Seven Sins: Vices or Virtues?

PEOPLE LOVE TO COMPLAIN about their memories. When I meet someone for the first time and the conversation turns to my research, I know
what's coming next. "You should study me;' my new acquaintance will almost invariably say with a shrug, especially if he or she is over age forty.
Then follows a list of exasperating recent encounters with absent-mindedness or name blocking, and finally a sigh of relief when I offer assurances
that these kinds of memory problems are common. The very pervasiveness
of memory's imperfections, amply illustrated in the preceding pages, can
easily lead to the conclusion that Mother Nature committed colossal blunders in burdening us with such a dysfunctional system. John Anderson, a
cognitive psychologist at Carnegie-Mellon University, summarizes the prevailing perception that memory's sins reflect poorly on its design: "over the
years we have participated in many talks with artificial intelligence researchers about the prospects of using human models to guide the development of artificial intelligence programs. Invariably, the remark is made,

'Well, of course, we would not want our system to have something so unreliable as human memory:"

It is tempting to agree with this characterization, especially if you've
just wasted valuable time looking for misplaced keys, read the statistics on
wrongful imprisonment resulting from eyewitness misidentification, or
woken up in the middle of the night persistently recalling a slip-up at work.
But along with Anderson, I believe that this view is misguided: it is a mistake to conceive of the seven sins as design flaws that expose memory as a
fundamentally defective system. To the contrary, I suggest that the seven
sins are by-products of otherwise adaptive features of memory, a price we
pay for processes and functions that serve us well in many respects.

To support this suggestion, I'll draw on evidence and ideas from a variety of sources, including evolutionary biology and psychology. Evolutionary psychology has sparked heated debates recently. Proponents of this
approach draw heavily on Darwin's ideas about natural selection in an attempt to explain cognition and behavior, claiming that the mind cannot be
understood fully without adopting an evolutionary perspective. They contend that the mind consists of a collection of specialized abilities that arose
to solve specific problems posed by the environment during the course of
evolution, and that natural selection is the primary mechanism responsible
for the mind's complex design. Evolutionary theorists contend further that
much of the mind's structure is specified innately by intricate genetic programs. From this perspective, the task of psychology is to engage in what
the cognitive psychologist and evolutionary theorist Steven Pinker calls
"reverse-engineering" :

In forward-engineering, one designs a machine to do something; in reverse-engineering, one figures out what a machine was designed to do.
Reverse-engineering is what the boffins at Sony do when a new product is announced by Panasonic, or vice versa. They buy one, bring it
back to the lab, take a screwdriver to it, and try to figure out what all the parts are for and how they combine to make the device work.

Critics of the evolutionary approach, in contrast, express concern
about several aspects of evolutionary theorizing. For example, they worry
that evolutionary ideas too often rely on large doses of speculation - and
too little on hard data. They question whether evolutionary theories can be
adequately tested in a way that allows us to understand the origins of a particular ability, or whether attempts at reverse-engineering have succeeded.
Some critics contend that evolutionary psychologists assign too much
weight to innate genetic programs when attempting to explain the mind's
abilities and complexities; others believe that the mind is better viewed as a
general-purpose problem solver than as a collection of specialized abilities.
And some critics wonder whether an evolutionary perspective really adds
anything to the nonevolutionary theories that psychologists construct in
their attempts to understand the working of the mind.

I'll return to some of these issues later in the chapter. Though I share
the critics' concerns regarding the testability of evolutionary claims, I've
drawn on evolutionary perspectives in earlier work, and have found that an
evolutionary orientation can serve as a rich source of suggestions and hypotheses. In previous chapters of this book, I focused on lessons that experimental research has taught us about each of the seven sins. In this chapter,
the spirit is more exploratory; I advance ideas about the origins of the
seven sins which can help us to place them in a broader perspective, think
thoughts that we might nOt otherwise consider, and appreciate why memory's vices can also be its virtues.

WHEN LESS IS MORE.

To illustrate the general thrust of my proposal, consider what Marc Hauser,
the Harvard evolutionary psychologist who studies animal behavior, calls
"intelligent errors." In his review of studies concerning spatial navigation in
various species, Hauser observes that animals sometimes make seemingly
bizarre mistakes when they navigate their environments. For instance, train
a rat to navigate a maze to find a food reward at the end, and then place a
pile of food halfway into the maze. The rat will run right past the pile of
food as if it did not exist, continuing to the end, where it seeks its just reward!

Why not stop at the halfway point and enjoy the reward then?
Hauser suggests that the rat is operating in this situation on the basis of
"dead reckoning" a method of navigating in which the animal keeps a
literal record of where it has gone by constantly updating the speed, distance, and direction it has traveled. A similarly comical error occurs when a
pup is taken from a gerbil nest containing several other pups and is placed
in a nearby cup. The mother searches for her lost baby, and while she is
away, the nest is displaced a short distance. When the mother and lost pup
return, she uses dead reckoning to head straight for the nest's old location.
Ignoring the screams and smells of the other pups just a short distance
away, she searches for them at the old location. Hauser contends that the
mother is driven by signals from her spatial system.

Though the behaviors in these examples seem perverse, they reflect
reliance on a type of navigation that serves the animals quite well in most
situations. The system is adapted to aspects of the animal's environment,
but can get the animal into trouble when things change in unexpected
ways. Fortunately, nests don't move in the real world that the animal inhabits; such confusing changes require the intervention of a cunning experimenter and tend not to occur in the wild.

Something similar occurs in the behavior known as imprinting. After
hatching, a baby chick treats the first moving object she encounters as her
mother. Because the first moving object that a chick encounters almost always is the mother hen, imprinting is an effective mechanism for ensuring
that a newborn chick follows its mother in order to receive proper feeding and care. But as shown by the student of animal behavior Konrad Lorenz,
when a baby chick first sees another moving object after hatching - a rolling red ball or a human (Lorenz used himself) - the animal imprints on
the object and follows along as it would normally follow the mother hen.
Consequently, a small flock of goslings often followed Lorenz. Imprinting
depends on a specialized memory mechanism that is adapted to the regularities of the chick's ordinary environment. Though usually adaptive, imprinting can cause problems for the chick if the mother is not the first
moving object that the bird encounters. But in nature, this event is highly
improbable.

I believe something similar is going on with memory's seven sins:
mechanisms that serve us well much of the time occasionally get us into
trouble. Of all the sins, seeing the positive side of persistence is perhaps easiest. Rene Descartes crystallized the issue several centuries ago. "The utility
of all the passions consists in their strengthening thoughts which it is good
that [the soul] preserve:' he observed. "So too all the evil they can cause
consists either in their strengthening and preserving those thoughts more
than necessary or in their strengthening and preserving others it is not
good to dwell upon." Although intrusive recollections of trauma can be
disabling, it is critically important that emotionally arousing experiences,
which sometimes occur in response to life-threatening dangers, persist over
time. The amygdala and related structures contribute to the persistence of
such experiences by modulating memory formation, sometimes resulting
in memories we wish we could forget. But this system boosts the likelihood
that we will recall easily and quickly information about threatening or
traumatic events whose recollection may one day be crucial for survival.
Remembering life-threatening events persistently - where the incident
occurred, who or what was responsible for it - boosts our chances of
avoiding future recurrences.

Transience, forgetting over time - also has an adaptive side. Forgetting can be frustrating, but it is often useful and even necessary to dismiss information that is no longer current, such as old phone numbers or
where we parked the car yesterday. As the psychologists Robert and Elizabeth Bjork have pointed out, information that is unimportant or no longer
needed will tend not to be retrieved and rehearsed, thereby losing out on
the strengthening effects of post-event retrieval and becoming gradually
less accessible over time.

John Anderson and his associates have taken this line of thinking even
further, arguing that forgetting over time reflects an optimal adaptation to
the structure of the environment. Anderson examined various situations
involving information retrieval and analyzed how the past history of using
a particular bit of information predicts its current use. He observed a regularity that parallels the form of transience in human memory: the demand
for a particular piece of information drops as greater periods of time pass
since its last use. For example, the Anderson group has noted that in library
systems, books that have been checked out recently or frequently in the past
are more likely to be requested at a specific present moment than books
that have been checked less recently or frequently. They observed something similar when they examined headlines in the New York Times for 730
days in 1986 and 1987, recording each time a particular word appeared. The
likelihood that a particular word would appear on a specific day fell as a
function of the time since it was last used. Anderson's group has found
similar parallels in other situations, including the use of words in conversations with children, and the likelihood of receiving an e-mail message from
a correspondent as a function of the time elapsed since earlier messages.

A system that renders information less accessible over time is therefore highly functional, because when information has not been used for
longer and longer periods of time, it becomes less and less likely that it will
be needed in the future. On balance, the system would be better off setting
aside such information - and transience leads to exactly that outcome.
Anderson suggests that the general form of forgetting documented in numerous experiments - the rate of forgetting slows down over time - reflects a similar function in the environment which relates past and present
use of information. According to Anderson, our memory systems have
picked up on this regularity, and in essence make a bet that when we
haven't used information recently, we probably won't need it in the future.
We win the bet more often than we lose it, but we are acutely aware of the
losses - the frustrations of forgetting - and are never aware of the wins.

The basic idea here resembles what scientists who study animal behavior in natural environments call a "trade-off." Think about a squirrel
that gingerly approaches a fractured cookie near a group of picnickers. The
squirrel bravely grabs a bit of the cookie and retreats to a nearby tree before
eating it. It returns several times and, on each occasion, grabs a cookie fragment, brings it back to the tree, and devours it. Though not the most efficient way to consume a cookie, this procedure allows the squirrel to re duce its exposure to possible predators. Researchers have indeed found that
squirrels are more likely to haul small pieces of cookie to cover than big
ones - big pieces take longer to eat than small ones, and thus place the
squirrel at greater risk. There is a trade-off between maximizing the benefits of feeding and minimizing the costs of encountering a predator; the
squirrel's behavior suggests that it is balancing the two. Similarly, in memory there is a trade-off between the benefit of reducing the accessibility of
information that hasn't been used recently or frequently, which probably
won't be needed in the future, and the annoyance or other costs of forgetting.

Some of the same ideas involving frequency and recency of usage also
apply to blocking in semantic memory, as seen most clearly in tip-of-thetongue states. Recall that people are most susceptible to blocking on names
and other bits of information that have not been used recently. Recall also
that blocking often results from a weakened connection between conceptual representations (things you know about a person or object) and
phonological representations (the sound of a word or name). Tip-of-thetongue states may thus reflect the principle articulated by Anderson's
group: information that has not been used recently begins to lose out
in memory because the odds are growing that it will not be needed. When
a connection between conceptual and phonological representations has
not been strengthened recently by using a word or a name, the link becomes ever more unreliable and we become correspondingly susceptible to
blocking.

Some types of blocking reflect the operation of inhibitory processes
that render information inaccessible (see Chapter 3). Psychologists and
neuroscientists have long recognized that inhibition is a fundamental feature of the nervous system: the brain relies on mechanisms that reduce activity as much as mechanisms that intensify it. Think about what might result without the operation of inhibition: a memory system in which all
information that is potentially relevant to a cue invariably and rapidly
springs to mind. Consider the following experiment. Try to recall an episode from your life that involves a table. What do you remember, and how
long did it take to come up with the memory? You probably had little difficulty coming up with a specific incident - perhaps a conversation at the
dinner table last night, or a discussion at a conference table at the office this
morning. Now imagine that the cue "table" brought forth all the memories
that you have stored away involving a table. There are probably hundreds
or thousands of such incidents. What if they all sprung to mind within seconds of considering the cue? A system that operated in this manner would
likely result in mass confusion produced by an incessant coming to mind of
numerous competing traces. It would be a bit like using an Internet search
engine, typing in a word that has many matches in a worldwide data base,
and then sorting through the thousands of entries that the query elicits. We
wouldn't want a memory system that produces this kind of data overload.
Robert and Elizabeth Bjork have argued persuasively that the operation of
inhibitory processes helps to protect us from such potential chaos.

The basic idea underlying the foregoing analyses of transience and
blocking is that as far as memory is concerned, less is sometimes more.
That same principle applies equally - if not more strongly - to absentmindedness. Absent-minded errors occur in part because establishing a
rich memory representation that can later be recollected voluntarily requires attentive, elaborate encoding. Events that receive minimal attention
and elaboration as they are occurring also stand little chance of being recollected subsequently. But what if all events were registered in elaborate detail, regardless of the level or type of processing to which they were subjected? The result would be a potentially overwhelming clutter of useless
details, as happened in the famous case of the mnemonist Shereshevski.
Described by the Russian neuropsychologist Alexander Luria, who studied
him for years, Shereshevski formed and retained highly detailed memories
of virtually everything that happened to him - both the important and
the trivial. Yet he was unable to function at an abstract level because he was
inundated with unimportant details of his experiences - details that are
best denied entry to the system in the first place. An elaboration-dependent system ensures that only those events that are important enough to
warrant extensive encoding have a high likelihood of subsequent recollection. Events that do not attract attention and elaboration are likely to be
less important and, hence, less likely to be needed for recall at a later time.

An elaboration-dependent system allows us to enjoy the considerable
benefits of operating on automatic pilot, without having memory cluttered
by unnecessary information about routine activities. As I discussed in
Chapter 2, tasks that initially require considerable attention and effort,
such as learning to drive a car, are eventually handled by automatic processes after sufficient practice, thereby freeing up resources for more im portant matters. It is surely infuriating when, operating on automatic pilot,
you put down a book or your wallet in an atypical location and later can't
remember where you left it. But suppose that when you misplaced the object, you were mentally absorbed in thinking about ways to cut costs in
your business, and came up with a great idea that saved you lots of money.
Operating on automatic led to an irritating incident of absent-minded forgetting, but because you were focusing attention on your business, you
gained a lasting benefit. When we can perform routine tasks by relying on
automatic processes, we are free to devote attention to more consequential
matters. Because we rely on automatic processes frequently in our daily
lives, the occasional absent-minded error seems a relatively small cost for
such a large benefit.

The "less is more" principle also applies to two of the sins involving
memory distortion: misattribution and suggestibility. I showed earlier that
many instances of misattribution and suggestibility reflect poor memory
for the source of an experience (see Chapters 4 and 5). When we don't recall
exactly who told us a particular fact, where we saw a familiar face, or
whether we actually witnessed an event or only heard about it later, the
seeds of memory distortion are sown. If we don't recall the exact source of
an experience - either because the details were not initially well encoded,
or because they fade over time - we become quite vulnerable to the misattributions considered in Chapter 4 which are associated with source confusions and cryptomnesia (unintentional plagiarism). We may also be vulnerable to incorporating suggestions made after an event regarding the
nature of specific details that we remember only vaguely. Accepting inaccurate suggestions can have grave consequences for eyewitness testimony, as I
showed in Chapter 5.

But what would be the consequences and costs of retaining the myriad of contextual details that define our numerous daily experiences? Assume, as I've argued, that memory is adapted to retain information that is
most likely to be needed in the environment in which it operates. We seldom need to remember all the precise sensory and contextual details of our
every experience. Would an adapted system routinely record all such details
as a default option, or would it carefully record such details only when circumstances warn that they may later be needed? Our memories operate on
the latter principle, and most of the time we are better off for it. We pay the
price, however, when we are required to recollect detailed source informa, 92 tion about an experience that did not elicit any special effort to encode
source details.

Some types of misattribution occur when we fail to recollect specific details of an experience, and at the same time recall the general sense
of what happened. In laboratory demonstrations of false recognition considered in Chapter 4, for instance, people incorrectly claimed that they previously heard the word sweet when in fact they had heard a group of semantically associated words, including candy, sugar, and taste. In related
experimental procedures, people claim to have seen a picture of a particular car or teapot earlier in the experiment, when they had actually seen pictures of physically similar but not identical cars and teapots. Misattribution
occurs because participants in these experiments respond on the basis of
memory for the general sense or gist of what they saw or heard.

However, the ability to remember the gist of what happened is also
one of memory's strengths: we can benefit from an experience even when
we do not recall all of its particulars. Indeed, studies conducted in my laboratory show that misattributions that result from remembering the gist are
signs of a healthy memory system. For instance, after studying semantically
associated words such as candy, sugar, and so forth, patients with amnesia
caused by damage to the hippocampus and nearby structures in the temporallobe remembered fewer of these words than did healthy control subjects - hardly a surprising result. But the amnesic patients were also less
likely than the controls to make the mistake of falsely recognizing semantically related words such as sweet, which had not been presented in the originallist. The same thing happened when amnesic patients studied pictures
of cars, teapots, and other objects: compared to healthy controls, they later
recognized fewer of the pictures they actually saw but were also less likely
to falsely recognize similar pictures they hadn't seen earlier. Temporal
lobe damage impaired patients' memories for both the particulars and
the gist of what they had experienced, resulting in reduced true and false
memories.

Memory for gist information is fundamental to such abilities as categorization and comprehension, allowing us to generalize across and organize our experiences. To develop a coherent category of "birds;' for example, it's important to learn that a cardinal and an oriole are both members
of the category despite superficial differences in their appearances. We need
to notice and retain the recurring features that unite all birds, and to ignore
the idiosyncratic details that differentiate among them. The cognitive psychologist James McClelland has developed a theoretical model in which
generalization results from retaining the gist of prior experiences. McClelland contends that generalization "is central to our ability to act intelligently:' Yet in his model McClelland also notes that "such generalization
gives rise to distortions as an inherent by-product."

This idea receives striking experimental support from a recent study
of false recognition in adults with a type of autistic disorder. Autism is associated with poor social skills, impaired communication abilities, and a
highly rigid, literal style of processing information. But autistic children
and adults can also show surprisingly good, and sometimes spectacular,
rote memory abilities, as illustrated some years ago by Dustin Hoffman's
character in the popular movie Rain Man. Despite his many limitations,
Raymond Babbitt was a repository of obscure facts, spewing forth such
nuggets as the name of the only major airline never to have suffered a crash
(Qantas).

Scientists have described autistic patients who show exceptional
memory for dates, names, or visual patterns. The neurologist David Beversdorf and his collaborators presented lists of semantically associated
words to autistic adults and to a nonautistic control group. On a later test,
the autistic subjects recognized just as many of the words they had studied
earlier as nonautistic subjects did. But the autistic group had fewer false
alarms than the non autistic group to semantically related words that they
hadn't studied earlier. The autistic group thus more accurately discriminated between true and false memories than cognitively intact subjects.

This pattern contrasts with that of the amnesic patients who showed
reduced true memories and reduced false memories. The autistic adults
were less likely than controls to generalize from the words on the study list.
They retained individual memories of the specific words they had studied,
but not the semantic gist that misleads cognitively normal adults down the
path of false recognition. A memory system that is not susceptible to gistdriven false recognition might free us from occasional bouts of misattribution. But it could also turn us into something like Raymond in Rain
Man, burdened by a rote record of trivial facts while remaining insensitive
to patterns and regularities in the environment which our memory systems
normally exploit to our benefit. False recognition is, in part, a price we may
pay for the benefit of generalization.

The sin of bias is also partly attributable to important strengths of our
cognitive systems. Stereotypical biases often lead to unwarranted evaluations of individuals based on accumulated past experiences with groups, as
we saw in Chapter 6. Though stereotypes can produce these undesirable
consequences, they also make our cognitive lives more manageable by promoting generalizations that, on average, are reasonably accurate. The social
psychologist Gordon Allport dearly saw this point back in the 1950S. He
characterized stereotypes as consequences of ordinary processes of perception and memory, "Iman's] normal and natural tendency to form generalizations, concepts, categories, whose content represents an oversimplification of his world of experience." Stereotypical biases constitute another
price we pay for memory processes that generalize across past experiences.

We also saw that bias often results in memories that depict the self in
an overly favorable light. Egocentric biases lead us to remember better
grades than we actually achieved, or to exaggerate in memory our contributions at work or at home. Consistency and change biases can help to justify our involvement in a relationship, and hindsight biases make us seem
wiser in retrospect than we actually were. On the face of it, these biases
would appear to loosen our grasp on reality and thus represent a worrisome, even dangerous tendency. After all, good mental health is usuallyassociated with accurate perceptions of reality, whereas mental disorders and
madness are associated with distorted perceptions of reality. But as the social psychologist Shelley Taylor has argued in her work on "positive illusions;' overly optimistic views of the self appear to promote mental health
rather than undermine it. Far from functioning in an impaired or suboptimal manner, people who are most susceptible to positive illusions generally
do well in many aspects of their lives. Depressed patients, in contrast, tend
to lack the positive illusions that are characteristic of nondepressed individuals. Remembering the past in an overly positive manner may encourage us to meet new challenges by promoting an overly optimistic view of
the future, whereas remembering the past more accurately or negatively
can leave us discouraged. Clearly there must be limits to such effects, because wildly distorted optimistic biases would eventually lead to trouble.
But as Taylor points out, positive illusions are generally mild and are important contributors to our sense of well-being. To the extent that memory
bias promotes satisfaction with our lives, it can be considered an adaptive
component of the cognitive system.

SEEKING THE SOURCES OF THE SEVEN SINS.

Up to now, I've used the word adaptive in a quite general sense, but to
explain the possible sources of the seven sins I need to clarify what I mean
when I say that a feature of memory is adaptive. Psychologists use the term
adaptation in at least two ways. One usage comes from evolutionary theory
and has a highly specific, technical meaning. An adaptation in this sense is
a feature of a species that came into existence through the operation of natural selection because it increased the reproductive fitness of individuals.
Darwin's argument for natural selection as the sole evolutionary mechanism to account for adaptive design rested on three fundamental observations. First, he observed that only a portion of each generation manages to
reproduce. Second, he noted that offspring are not identical to their parents
- some are taller, faster, or stronger than others. Variations like these that
can be passed on to subsequent generations are considered heritable. Third,
Darwin argued that some aspects of heritable variation raise the likelihood
that their bearers will survive and reproduce. Features of an organism that
result from natural selection are adaptations.

However, psychologists often use the term "adaptation" in a looser
manner - a colloquialism that refers to a feature of an organism that has
generally beneficial consequences, whether or not it arose directly in response to natural selection during the course of evolution. Within the domain of memory, for instance, recalling telephone numbers and learning to
use a computer provide examples of this looser sense of an adaptive feature. We can remember frequently used telephone numbers reasonably
well, and in that sense memory can be considered adapted to the task. But
telephones are such a recent invention that this ability could not have
arisen during the course of evolution as an adaptation produced by natural
selection. The same goes for the abilities needed to learn to use a computer
or any other type of modem technology: our memory systems allow us to
accomplish these tasks, but memory cannot have arisen as an adaptation
for learning to operate modern technology.

The Harvard paleontologist Stephen Jay Gould has used the term
exaptation to refer to "features that now enhance fitness, but were not built
by natural selection for their current role." Exaptations are, in effect, adaptations that are co-opted to perform functions other than the one for which
they were originally selected. For instance, evolutionary biologists believe
that the feathers of birds likely evolved initially as adaptations to perform
such functions as thermal regulation or capturing prey, and were only later
co-opted for the entirely different function of flight. In human cognition,
the ability to read is an example of an exaptation. Because significant portions of the population have begun to read only during the past few centuries, reading is too new to be a product of natural selection. But reading
draws on basic visual and cognitive abilities that likely arose as adaptations.
Similarly, our abilities to remember telephone numbers and to use computers are not themselves evolutionary adaptations, but draw on features of
memory that presumably originated as adaptations.

Gould and his Harvard colleague Richard Lewontin delineated a third
type of evolutionary development called a "spandrel" - a special type of
exaptation that is an unintended consequence or by-product of a particular
feature. Whereas the exaptations discussed previously originated as adaptations, and were later hijacked to perform a different function, spandrels
have no adaptive function from the outset. The term spandrel is used in architecture to designate the leftover spaces between structural elements in a
building. As an example, Gould and Lewontin described the four spandrels
in the central dome of Venice's Cathedral of San Marco: spaces between
arches and walls that were subsequently decorated with four evangelists
and four biblical rivers. The spandrels were not designed for the specific
purpose of housing these paintings, although they do so quite well. Similarly, people seeking shelter can sleep in the spaces between pillars of a
bridge, even though the pillars and spaces were not put there in order to
provide shelter.

Determining whether particular features of the human mind are adaptations, exaptations, or spandrels is a difficult task that has turned into a
kind of blood sport in contemporary psychology and biology. Evolutionary
psychologists have sought to explain human cognition and behavior in
terms of adaptations preserved by natural selection. "The mind is a system
of organs of computation, designed by natural selection to solve the kinds
of problems our ancestors faced in their foraging way of life," contends Steven Pinker, an enthusiastic advocate of the evolutionary perspective. The
psychologist Leda Cosmides and the anthropologist John Tooby, pioneers
of evolutionary psychology, argue in a similar spirit. "The human mind
consists of a set of evolved information-processing mechanisms in the human nervous system;' they assert. "These mechanisms, and the developmental programs that produce them, are adaptations, produced by natural
selection over evolutionary time in ancestral environments."

In contrast, critics of evolutionary psychologists, including Stephen
Jay Gould, maintain that it is too easy to come up with after-the-fact explanations of mind and behavior that appeal to adaptations and natural selection - what have come to be known as "just so" stories. Gould holds that
many current features of the human mind are exaptations and spandrels
- in addition to reading, other examples include writing and religious beliefs. He argues that exaptations and spandrels are such dominant influences in shaping the contemporary human mind that they constitute "a
mountain to the adaptive molehill." Debates between advocates of these
contrasting perspectives, exemplified by a 1997 exchange in the New York
Review of Books between Pinker and Gould, are often quite contentious.

For evolutionary accounts of mind in general and memory in particular to amount to more than speculative exercises in post hoc storytelling,
debates about the relative importance of adaptations, exaptations, and
spandrels will have to be settled by empirical tests of hypotheses and predictions generated by alternative positions. Experimental psychologists
such as myself tend to require hard evidence from controlled studies to decide between competing hypotheses. Although we do not have direct access
to the evolutionary record of human cognition - there were no psychologists recording observations of our ancestors' behaviors in ancient environments - that doesn't preclude rigorous testing of evolutionary hypotheses.

The University of Texas psychologist David Buss and his associates
have recently provided a helpful discussion of how such testing might proceed. They provide thirty examples in which predictions from an evolutionary perspective anchored by ideas of adaptation and natural selection
led to empirical discoveries about human behavior or cognition. The cited
examples include the nature of male sexual jealousy, patterns of spousal
and same-sex homicide, relationship-specific sensitivity to betrayal, and
mate guarding as a function of female reproductive value.

To test for evolutionary adaptations, psychologists and biologists rely
on several types of evidence and considerations. One criterion is that of
complex or special design: a feature of an organism is likely to be an adaptation if its internal structure is so complex as to minimize the possibility
that the feature arose by chance or as an incidental by-product of something else. The vertebrate eye is a classic example of complex design. Intricate interdependencies among its many parts make it highly likely that the
eye was designed by natural selection to accomplish the task of seeing, and
highly unlikely that it developed by chance or as an incidental by-product.
In the early nineteenth century, the theologian William Paley argued that
such complex design reflects the presence of a designer with foresight. Invoking a comparison with a watchmaker, Paley noted that the intricate
structure of a watch, like that of a living organism, reveals the presence of
design that is devoted to specific functions, and cannot be attributed to a
fortuitous alignment of all the different parts in just the right arrangement.
In his book The Blind Watchmaker, the biologist Richard Dawkins offered a
Darwinian twist on Paley's watchmaker argument. A true watchmaker sets
out with the goal of designing a watch, Dawkins observed, but natural selection is blind - it has no goal, purpose, or foresight.

Adaptations lead to differential reproductive success. It therefore follows that if a specific trait or feature has been favored by selection, it should
be possible to find some evidence in the numbers of offspring produced by
the trait's bearers. For instance, the hypothesis that women prefer to mate
with tall men recently received support from the finding that tall men bear
more offspring than short men. Physical stature in men may thus be, in
part, an adaptation produced by selection.

The operation of natural selection may also be indicated when a trait
turns up consistently in different species. Consider, for instance, the case of
bodily symmetry. Humans and other organisms vary in the degree to
which their bodies deviate from perfect left-right symmetry. In studies
where raters judge attractiveness, greater bodily symmetry is generally associated with higher ratings. Further, symmetry produces advantages in
sexual competition over asymmetry across a wide variety of nonhuman
species, including insects, birds, and primates. Biologists have found that
asymmetry is associated with the existence of genetic abnormalities and
with exposure to negative environmental events, such as parasites and pollutants. Combining these observations with the sheer pervasiveness of selection for individuals with high symmetry across different species, there
are grounds for arguing that bodily symmetry is an adaptation produced
by natural selection. Though this idea is not accepted by all researchers - a
controversy exists concerning how symmetry and asymmetry come about
- the findings point toward the operation of selective pressures.

An adaptation may also be signaled by the presence of what anthropologists call human universals: traits that are present in all recorded human cultures. For example, cross-cultural studies indicate that physical attractiveness is widely valued by both men and women (although more by
men) and that people from different cultures tend to agree in their judgments of facial attractiveness. Aspects of facial attractiveness have, in turn,
been associated with greater physical and mental health, raising the possibility that it may be an evolutionary adaptation.

The fact that a feature is a universal does not necessarily indicate that
it arose as an adaptation. The anthropologists Donald Brown and Steven
Gaulin each point out that universals can also arise from cultural traits that
are ancient and highly useful, and therefore have spread through many societies. For example, the use of fire (particularly for cooking) is a human
universal. However, we do not need to postulate that the use of fire reflects
the operation of a shared adaptation. It's simpler to argue, as both Brown
and Gaulin do, that people have long been exposed to fire and recognize its
usefulness. But as Gaulin points out, if this type of cultural explanation can
be ruled out, then the remaining universals can help to guide the search for
psychological adaptations.

Conversely, if a trait is universally present across cultures with a single
exception, that exception does not necessarily rule out the existence of an
adaptation; there could be other cultural factors operating that help to explain the exception. On balance, then, while universals do not provide
definitive evidence for (or against) adaptations, they can serve as helpful
guideposts.

How about memory and the seven sins? Though we don't have a great
deal of evidence on which to base strong claims about evolutionary origins,
some relevant data come from studies of gender differences. Consider one
evolutionary hypothesis about memory noted in the article by Buss and coworkers: women have more accurate memories for the spatial locations
of objects than men do. The Canadian psychologists Marion Eals and
Irwin Silverman noted that archeological and paleontological data from
the hunter-gatherer period, one of the important epochs when human cognition evolved, suggest that men engaged primarily in hunting whereas
women primarily foraged. Eals and Silverman hypothesized that these different activities placed different demands on spatial cognition and memory. Specifically, they suggested that successful foragers must locate food
sources that are embedded within complex arrays of vegetation, and remember those locations for later visits. Natural selection therefore should
have favored the development of superior memory for the spatial location
of objects in women compared to men.

Eals and Silverman tested this hypothesis by showing men and women
spatial arrays of objects. In one experiment, the objects appeared in a drawing; in another, they were dispersed on desks and tables in a room. In both
experiments, women remembered the locations of objects more accurately
than did men. But men outperformed women on other spatial tasks that,
according to Eals and Silverman, tap spatial abilities that would have been
required for successful hunting.

Some subsequent studies have replicated Eals and Silverman's results,
whereas others have placed various qualifications and limitations on the
findings. The question of whether spatial memory abilities in women are
adaptations produced by selection for foraging skills is, accordingly, not yet
settled. Nonetheless, these studies provide an example of how evolutionary
hypotheses about the origins of memory can be formulated and tested.

A related type of evidence hinting at selection for sex differences in
spatial memory abilities comes from research by the psychologist David
Sherry at the University of Western Ontario, who has studied memory in
various bird species, including brown-headed cowbirds. When they breed,
female cowbirds lay a single egg in another species' nest, and then spend the
rest of the day searching for other nests in which they can lay eggs during
the coming days. Females must remember the location of the nests, as the
males do not help the females to locate nests (in other cowbird species,
both sexes playa role in such nest hunting).

In earlier studies, Sherry and others had demonstrated that the avian
hippocampus plays a key role in allowing food-storing birds to remember
where they have hidden food. A Clark's nutcracker, for instance, stores as
many as thirty thousand seeds in five thousand locations during the fall, retrieving them the next spring. The bird accomplishes this daunting recall
task with great success. Overall, the hippocampus is consistently larger in
species that store and retrieve food than in those that do not. Further, after
damage to the hippocampus, food-storing birds have great difficulty remembering the locations of their food caches.

If the avian hippocampus is important for spatial memory, Sherry
reasoned, then female brown-headed cowbirds ought to have a relatively
larger hippocampus than male brown-headed cowbirds as a consequence
of selection for spatial ability in the females related to finding and remembering nest locations. Measurements of hippocampal volume in relation to
the overall size of cowbirds' brains revealed exactly that: the hippocampus
is indeed relatively larger in females than males. No such sex differences
were found in two closely related species of birds that do not lay eggs in
other birds' nests.

Studies of spatial abilities in other species show that the direction of
sex differences can be reversed when selection pressures favor the development of spatial learning in males. Steven Gaulin at the University of Pittsburgh examined two types of male rodents: a polygamous meadow vole
that expands its home range during breeding season to increase mating opportunities, and a monogamous prairie vole that does not. Expanding its
home range should produce selection for spatial abilities in the polygamous meadow vole. When Gaulin tested the two types of voles in laboratory maze learning tasks, he found evidence for superior spatial abilities in
male compared with female meadow voles, and no sex difference among
prairie voles. The hippocampus was also larger in male than female
meadow voles, but no difference existed in hippocampal size between male
and female prairie voles.

The work of Gaulin, Sherry, and their associates strongly supports the
general idea that some features of memory are adaptations produced by
natural selection. I'm not aware of any comparable evidence that speaks directly to the origins of the seven sins. Back in the 1980s, David Sherry and I
coauthored a theoretical article arguing that some features of memory are
adaptations produced by selection whereas others are exaptations; we tried
to identify characteristics of each. I take the same approach to the seven
SinS.

The most probable candidates for adaptations are persistence and
transience. To the extent that persistence originated as a response to lifethreatening situations that posed a direct threat to survival, animals and
people who were able to remember those experiences persistently would
surely be favored by natural selection. This ability seems so basic that if it
did originate as an adaptation, we would expect many species to have neural machinery dedicated to preserving the memory of life-threatening experiences for long periods of time. As noted earlier, the universal presence
of a particular feature across numerous cultures does not necessarily indicate that the feature is an adaptation, but it does provide one telltale sign
of an adaptation. The neurobiologist Joseph LeDoux has noted that the
amygdala and related structures are involved in long-lasting fear learning
across diverse species, including humans, monkeys, cats, and rats. Likewise,
we might also expect to observe links among persistence, the amygdala,
and arousing or threatening experiences across diverse cultures and social
groups. I am not aware of any evidence that addresses this issue directly,
but cross-cultural studies examining neurobiological and cognitive aspects
of persistence represent a promising avenue for future research. Consider
also that, as discussed in Chapter 7, persistence results from a finely tuned
interplay between the amygdala and stress-related hormones which modulates memory formation - an interdependent system that is suggestive of
complex design.

The arguments of John Anderson and his group support the possibility that transience, too, could be an evolutionary adaptation. As mentioned
earlier, Anderson's argument rests on the idea that properties of transience
reflect properties of the environment in which memory operates. There is a
catch here, however. If transience is an adaptation that arose through selection, then its properties should reflect those of the ancient environments
in which our ancestors evolved. But how could we ever know about the
relevant properties of environments during the hunter-gatherer period
or other even earlier periods that may be relevant to human evolution?
Not easily. Some anthropologists study contemporary foraging groups that
remain culturally isolated, such as the Matsigenka indigenous people in
southeastern Peru. If patterns of information retrieval in such groups could
be examined, the results would help to determine whether transience reflects properties of environments more akin to ancestral environments,
rather than modern Western societies. I am not aware of any such studies.
However, the cognitive psychologist Lael Schooler, who has collaborated
with Anderson on the idea that memory reflects environmental properties,
has tried to get at the issue from a different but related angle.

Schooler drew on data collected by his collaborators Ramon Rhine
and Juan Carlos Serio Silva concerning primate behavior in two separate
environments that are similar in important respects to environments in
which our hominid ancestors evolved: a tropical forest and a savanna. They
studied the ranging behavior of howler monkeys living in a tropical forest
on the volcanic island of Agaltepec in Mexico, and baboons living in the savanna and open plains of Mikumi National Park in Tanzania. At both sites,
the researchers observed the ranging behavior of troops of howlers and baboons over a period of several months as they moved from location to location. Schooler, Rhine, and Silva then analyzed the likelihood that a troop
would return to a particular location as a function of the number of days
that had passed since they were last there. The probability of returning to a
particular location declined as time went on, and the form of the curve was
similar to that observed for forgetting. As with the modern environments
studied by Anderson and Schooler, the tropical forest of Agaltepec and the
savanna of Mikumi appear to be environments in which it is an increasingly good bet to forget about information that hasn't been used for everlonger periods of time. We don't know whether the similar patterns are
based on independent mechanisms in modern humans and ranging primates, or whether they reflect a common evolutionary origin. Nonetheless,
these observations encourage the view that transience is an adaptation to
enduring properties of environments inhabited by both modern and ancient primates.

In her analysis of positive illusions, Shelley Taylor has suggested that
overly optimistic biases may also be evolutionary adaptations. However,
the University of Pennsylvania psychologist Steven Heine and his collaborators have presented evidence that casts some doubt on this possibility.
They suggest that biases to view the self in an overly positive manner are
specific to certain cultures. For example, they cited anthropological, sociological, and psychological evidence that the Japanese tend to adopt a critical view of the self, rather than the positive bias commonly seen in studies
of North Americans. If positive biases were evolutionary adaptations, we
would expect to observe such biases across cultures. Although, as noted
earlier, a single exception to a universal pattern does not rule out the possibility of an adaptation, this line of work suggests that cross-cultural studies
of the various forms of memory bias could prove to be highly informative.

Bias is closely related to high-level cognitive operations and complex
social interactions (see Chapter 6). These are precisely the kinds of processes that we would expect to vary considerably among cultures. Based on
the work of Heine's group, I predict that the specific form of memory biases will be found to vary considerably across cultures, and is more likely
the product of social and cultural norms than biological evolution produced by natural selection. It is still possible, however, that people in all
cultures exhibit some type of bias during remembering, with the particular
type or content of bias varying across cultures. Even if this is so, however, I
hypothesize that bias is an incidental by-product of the fact that general
knowledge and beliefs frequently guide acts of remembering.

I hypothesize that the remaining sins - blocking, absent-minded204 ness, misattribution, and suggestibility - are most likely evolutionary
spandrels. Part of my reasoning is driven by plausibility considerations: it
is difficult to imagine how or why natural selection would design a system that is especially prone to absent-minded errors, frequently blocks on
names or words, or remembers events that never occurred. But we have already seen that each of these sins can be plausibly viewed as a by-product
of useful features of memory that themselves arose as either adaptations or
exaptations. Absent-minded errors, misattribution resulting from source
memory confusion, and related effects of suggestibility are, I suggest, byproducts of adaptations and exaptations that produced a memory system
that does not routinely preserve all the details required to specify the exact
source of an experience. Blocking may be an incidental by-product of effects related to recency and frequency of information retrieval that also give
rise to transience. And gist-based false memories are by-products of categorization and generalization processes that are themselves vital to our
cogniti'/e function.

There is a difference, however, between these spandrels of memory
and the architectural spandrels discussed by Gould and Lewontin. Architectural spandrels have benign consequences: they do not interfere with or
undermine a building's structural or functional integrity. Not so for memory, however. The irritation of absent-minded errors, the momentary frustration of blocking, and the potentially shattering consequences of eyewitness misidentifications and false memories resulting from misattribution
or suggestibility all have the power to disrupt our lives, temporarily or permanently. When suffering the consequences of these spandrels gone awry,
it is difficult to appreciate or imagine that they are by-products of processes
that, for the most part, keep our cognitive lives running smoothly. It may
be helpful to think of these memory spandrels in relation to the squirrel
that weighs the benefits of feeding against the possible costs of encountering a predator and returns to cover repeatedly with bits of cookie. The misbegotten spandrels represent the cost of a trade-off in memory which also
has important, though less visible, benefits.

If my suggestions about the origins of the seven sins have merit, one
thing we can count on is that the sins are not going to disappear any time
soon. Recall the case of Binjimin Wilkomirski: he "remembered" childhood
terrors experienced in a Nazi concentration camp, when he actually appears to have lived safely in Switzerland during the war. The prospect of
someone falsely recollecting that he endured one of the greatest horrors
imaginable seems so bizarre that one is tempted to write off Wilkomirski as
an inexplicable, one-time aberration. But if misattribution and suggestibility, the likely culprits in Wilkomirski's delusions, are truly evolutionary
spandrels, then Wilkomirksi should not be an isolated case. And he is not.
Women and men who once believed that they had recovered memories of
terrible childhood traumas, only to later retract them after ending psychotherapy, remind us that Wilkomirski's experience is far from unique. So,
too, do the legions of self-proclaimed alien abductees, who vividly remember impossible events such as sexual abuse at the hands of demonic - and
elusive - alien captors. Suggestive procedures such as hypnosis are frequently implicated in such cases.

These types of false memories are nothing new. In Chapter 4, we considered the debate over false memories and deja vu which raged in the
1890s. As early as 1881, the British psychologist James Sully devoted an entire chapter of his book, Illusions: A Psychological Study, to "illusions of
memory," citing case after case of memory distortions that exemplify what
I call misattribution and suggestibility. The historian Patrick Geary described an eleventh-century Bavarian monk named Arnold who "remembered" encountering a flying dragon on a journey he made years earlier. Arnold's false memory was likely the product of imagination and suggestion.
Misattribution and suggestibility have been with us for a long time, and
will surely continue their mischief in the future.

The same applies to the other sins. Consider, for instance, transience
and persistence. People have been trying to overcome the limitations of
transience for centuries. As I noted in Chapter 1, the invention of visual imagery mnemonics - a method of improving memory by encoding new information in the form of vivid visual images - dates to the Greeks. Similarly, persistence has a long heritage. Recall Robert Burton's description of
the terrified Blasius, a reporter who witnessed the ancient earthquake at
Sacai, and for years afterward could not "drive the remembrance of it out
of his minde" (see Chapter 7). Post-traumatic stress disorder - where the
effects of persistence are painfully magnified - has achieved recognition
only recently from psychologists and psychiatrists. Yet its symptoms have
probably been around as long as people have experienced trauma. This idea
is wonderfully illustrated by the psychiatrist Jonathan Shay's compelling
book, Achilles in Vietnam, which delineates parallels between the aftermath
of combat trauma in Vietnam and in Homer's Iliad. Shay relates an incident where Achilles is overwhelmed by grief because he failed to cover for a
fellow soldier who died, and feels "pierced by memory" as he intrusively remembers his fallen comrade.

Even though they often seem like our enemies, the seven sins are an
integral part of the mind's heritage because they are so closely connected to
features of memory which make it work well. The seemingly contradictory
relationship between memory's sins and virtues captured the attention of
Fanny Price, the heroine of Jane Austen's nineteenth-century novel Mansfield Park. Admiring a beautiful shrub-lined walkway that had emerged
from a formerly rough patch of ground, Fanny recalled what the walkway
had looked like years earlier, and wondered whether she would lose this
memory in the future. The moment inspired her to contemplate seemingly
contradictory properties of memory:

If anyone faculty of our nature may be called more wonderful than the
rest, I do think it is memory. There seems something more speakingly
incomprehensible in the powers, the failures, the inequalities of memory, than in any other of our intelligences. The memory is sometimes
so retentive, so serviceable, so obedient; at others, so bewildered and so
weak; and at others again, so tyrannic, so beyond control! We are to be
sure a miracle every way - but our powers of recollecting and of forgetting, do seem peculiarly past finding out.

Modern psychology and neuroscience have proven Fanny wrong on
one point - that our powers of recollecting and forgetting are "peculiarly
past finding out" - but her acute appreciation of memory's contrasting
strengths and weaknesses could hardly be more apt. The seven sins are not
merely nuisances to minimize or avoid. They also illuminate how memory
draws on the past to inform the present, preserves elements of present experience for future reference, and allows us to revisit the past at will. Memory's vices are also its virtues, elements of a bridge across time which allows us to link the mind with the world.