Chapter 1
Lesson 1: Necessary and Sufficient Conditions
The neurologist, Oliver Sacks, in his book, The man who mistook his wife for a hat and
other clinical tales (1974), presented the case of a woman who, over the period of a few
days, developed some very unusual
Christina was a strapping young woman of twenty-seven, given to hockey and riding,
self-assured, robust, in body and mind... She had an active, full life--had scarcely known
a day's illness. Somewhat to her surprise, after an attack of abdominal pain, she was
found to have gallstones, and removal of her gallbladder was advised. She was admitted
to hospital three days before the operation date, and placed on an antibiotic [to prevent
bacterial infection]....
The day before surgery Christina ... had a disturbing dream of peculiar intensity. She was
swaying wildly, in her dream, very unsteady on her feet, could hardly feel the ground
beneath her, could hardly feel anything in her hands, found them flailing to and fro, kept
dropping whatever she picked up. She was ... so distressed [by the dream] that we
requested an opinion from the psychiatrist. "Pre-operative anxiety," he said. "Quite
natural, we see it all the time."
But later that day the dream came true. Christina did find herself very unsteady on her
feet, with awkward flailing movements, and dropping things from her hands. The
psychiatrist was again called.... "Anxiety hysteria," he now snapped, in a dismissive tone.
"typical conversion symptoms [conversion disorder is a mental disorder in which some
claim that anxiety due to unconscious psychological conflicts is transformed into sensory
or movement problems]....
But the day of surgery Christina was still worse. Standing was impossible--unless she
looked down at her feet. She could hold nothing in her hands, and they 'wandered'--unless
she kept an eye on them. When she reached out for something, or tried to feed herself, her
hands would miss, or overshoot wildly, as if some essential control or coordination was
gone. She could scarcely even sit up--her body 'gave way'. Her face was oddly
expressionless and slack, her jaw fell open, even her vocal posture was gone.
"Something awful's happened," she mouthed, in a ghostly flat voice. "I can't feel my
body. I feel weird--disembodied." (Sacks, 1974, pp. 44-45)
What caused this woman to develop the inability to feel her body? Was the psychiatrist
correct: was the problem caused by anxiety and her inappropriate attempts to deal with it?
If so, what precisely does this mean? How and under what conditions can anxiety cause a
physical problem?
Perhaps the cause involved some other factor (a factor is an event or condition that
causes something to occur). For example, perhaps it had something to do with the
antibiotics the woman was taking. But, if so, why did the antibiotics affect her in this
way? Why do antibiotics not do this to other people who take them?
Finally, she could have been affected by a factor unrelated to her planned surgery-perhaps a virus that, simply by coincidence, infected her at this time. But again, why
would a viral infection affect her in such an unusual way?
Perhaps the best explanation might be to suppose that several factors working together
led to the development of this woman's strange symptoms. In this case, could we call
each of the individual factors a "cause," even though none of them acting alone could
produce the symptoms?
It seems that, as we speculate more and more about possible causes of this woman's
feeling of disembodiment, we are led to more and more questions about what it means to
say that something is a cause. For example, if it were found that the antibiotics had
caused her feeling of disembodiment, would you conclude that antibiotics cause people to
feel as if they are disembodied? Why or why not? Most of you probably would answer
"no" and then argue that, because antibiotics don't generally cause such symptoms in
people, it would not make sense to say that "antibiotics cause people to feel
disembodied."
On the other hand, you might conclude that antibiotics caused the woman's symptoms;
and perhaps could even cause them in people who are especially sensitive to their effects.
But, in this case, if a factor influences the development of a disorder only in a very small
number of people, what does it mean to refer to that factor as a "cause"?
What Is A Cause?
That anyone would ask such an apparently simple-minded question may surprise you. As
you read it, you may have thought, "it's obvious what a cause is! It's like when one car
hits another and causes a dent: the dent is caused by the first car hitting the second car.
It's easy! A cause is a force that changes something else." Although this definition makes
some sense when we are talking about the causes of large-scale events in the physical
world, the issue quickly becomes more complicated when we consider other kinds of
phenomena (a phenomenon is any event that can be observed or measured in some
way). This is especially true when we consider the causes of nonphysical events such as
thoughts and emotions. So, let's examine some ideas that may help us to better
understand what is meant by the word "cause" in psychology.
Sufficient Conditions
In everyday life, most of us think of a cause as something that, if it is present, then the
effect will follow inevitably. For example, if I press the power button on the remote
control, the television will turn on; and we would expect that, any time the power button
is pushed, the television inevitably will light up. As another example, you might state that
a fire was caused by throwing a lit match into a wastebasket full of paper. By saying this,
you are implying that, anytime a lit match is thrown into a wastebasket, a fire will
develop. These examples suggest that, in everyday life, we tend to think of a cause in
terms of a "sufficient condition." A sufficient condition is one that, if present, will
always lead to the development of the event. In other words, "if I do this, this other
thing is going to happen, no doubt about it."
What we often fail to consider, however, is that sufficient conditions tend to be very
complex. For example, pressing the power button will not turn the television set on unless
some other things also are true:
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


the batteries in the remote control are charged
the remote control is within a certain distance of the television
the remote control is pointed in the general direction of the television
the television is in working order
There are still other factors that must be present if pressing the power button is going to
turn on the television (see Question 1-1 below). Thus, as you can see, a sufficient
condition for turning on a television actual involves the co-occurrence of a number of
individual factors. In a similar way, a lit match thrown into a wastebasket full of paper
will not be sufficient to cause a fire if the paper is wet. The general problem that these
examples point to is this: our notion of cause in everyday life is too simplistic. That is, we
tend to ignore many of the additional factors that also must occur if one particular factor
is to act as a cause of something else. Each factor contributes to the outcome, but none
alone is sufficient for the effect to occur.
Although you might think that the ultimate goal of research in psychology is to discover
sufficient conditions for causing specific changes in mental and behavioral phenomena,
this is not always, and probably not even often, the case. As you will see as you read the
textbook, individual researchers typically have much more modest goals for their work.
Necessary Conditions
Some of the factors included in the set making up a sufficient condition may be thought
of as "necessary conditions." A necessary condition is one that, if it does not occur,
then the event cannot occur. For example, in order for a fire to develop by throwing a
lit match into a wastebasket full of paper, there must exist an adequate supply of oxygen
in the space around the wastebasket. Because a fire cannot develop in the absence of
oxygen, oxygen is a necessary--but not a sufficient--condition for a fire. To take another
example, one must obtain a lottery ticket if one hopes to win the lottery. Thus, obtaining
a lottery ticket is a necessary condition for winning the lottery, but it definitely is not a
sufficient condition.
Again, although you might think that psychologists are trying to determine the necessary
conditions for the occurrence of mental and behavioral phenomena, this is not often the
case. Instead, psychologists typically try to find individual factors that tend to lead (that
is, to lead on average) to changes in mental and behavioral phenomena. In other words,
they try to find factors that increase or decrease the likelihood that a particular
mental or behavioral event will occur.
Critical Thinking Questions
Question 1-1
(a) In the example of the remote control presented above, think of some other factors that
also must be present in order to make pressing the power button a sufficient condition for
turning on a television.
Suggested Answer
(b) In the example of the lit match presented above, think of some other factors that also
must be present in order to make throwing it into a wastebasket full of paper a sufficient
condition for creating a fire.
Suggested Answer
(c) In the example of the lottery ticket presented above, think of some other factors that
also must be present in order to make buying one a sufficient condition for collecting the
lottery winnings.
Suggested Answer
Question 1-2
In the textbook, reference was made to the "paradox of progress": the idea that, although
there has been enormous progress in modern times with respect to knowledge,
technology, and the general economic situation, many people still seem to feel that the
quality of their lives and their sense of personal fulfillment have decreased. The question
was then asked: "What is the cause of this paradox?" Several answers were sketched:
disorganized value systems, rapid cultural changes, and the complex nature of modern
life all were suggested as possible causes of the paradox of progress.
Are any of these factors sufficient conditions for causing the feeling that the quality of
our lives and our sense of personal fulfillment have decreased? Why or why not? Are any
of these factors necessary conditions for causing the feeling that the quality of our lives
and our sense of personal fulfillment have decreased? Why or why not?
Suggested Answer
Question 1-3
A problem that you will discover in some psychological theories is that they propose a
"cause that explains (almost) everything." For example, critiques of the codependency
phenomenon have argued that some codependency theorists tend to blame addiction and
codependence for virtually every conceivable type of psychological problem. Based on
what you have learned about necessary and sufficient conditions, examine the claim that
codependency causes "virtually every conceivable type of psychological problem."
Suggested Answer
Question 1-4
Chapter 1 in the textbook lists and describes some general guidelines for thinking
critically. To which guideline or guidelines does the present critical-thinking lesson
apply?
Suggested Answer
Bibliography and References
Brown, C. W., & Ghiselli, E. E. (1955). Scientific method in psychology. New York:
McGraw-Hill.
Castillo, R. J. (1997). Culture and mental illness: A client-centered approach. Pacific
Grove, CA: Brooks/Cole.
Kaminer, W. (1992). I'm dysfunctional, you're dysfunctional. Reading, MA: AddisonWesley.
Sacks, O. (1987). The man who mistook his wife for a hat and other clinical tales. New
York: Harper & Row (Perennial Library).