Critical Thinking
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." Althoughthis 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:
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 researcherstypically 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 intoa 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
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
On page 2 of 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 ofpersonal 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, in the discussion of codependency in your textbook (pp. 4-6), it was stated that some codependency "theorists tend to blame addiction and codependence for virtually every conceivable type of psychological problem" (p. 5) 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
Figure 1-2 in the textbook (page 10) 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: Addison-Wesley.
Sacks, O. (1987). The man who mistook his wife for a hat and other clinical tales. New York: Harper & Row (Perennial Library).
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Lesson 2: The Methods of Agreement and Difference
The Methods of Agreement and Difference
In the previous lesson, we began to discuss the meaning of the term "cause" and to develop a way to think about causes in psychology--a discussion that will be continued in Lesson 3. In the present lesson, we will begin to discuss the methods (the specific procedures) psychologists use to identify causes--a discussion that also will be continued in futurelessons.
John Stuart Mill was an English philosopher of the nineteenth century who described a number of methods for finding causal factors. Let's look at two of his methods: the "method of agreement" and the "method of difference" (although Mill described other methods, they basically are variations on these two).
Mill's Method of Agreement
With the method of agreement, one looks for events that occur whenever the phenomenon being studied occurs. The single event that is found to be common to all occurrences of the phenomenon is said to be the cause. For example, some people who receive damage to their brainshave trouble remembering new facts--that is, they suffer from a certain kind of amnesia. If we selected a group of these amnesic people, we mightfind the following types of brain damage:
What is the one damaged structure common to all of these amnesic patients? It is the hippocampus. Based on evidence such as this, you might infer that the hippocampus is important in some way for memory formation.
This example refers to five case studies. On page 16 of the textbook, a case study was defined as "an in-depth investigation of an individual participant." It was noted that, if "researchers have a number of case studies available, ... they can look for threads of consistency among them, and they may be able to draw some general conclusions" (p.16). By looking for consistencies (commonalities) among the various cases, researchers are making use of the method of agreement.
But the method of agreement poses a major difficulty for those who want to use it to discover causes: a particular event that occurs each time a phenomenon occurs is not necessarily a cause of that phenomenon. For example, whenever the phone rings, it is almost always the case that,if I pick up the receiver, someone will speak to me through it. The ringing of the phone is the only event I am able to observe that occurs each time someone is on the other end. Nevertheless, we all know that the ringing does not cause someone to be on the line.
Let's look at another example. Christensen (1994) described the imaginary case of a man who was trying to discover what made him feel intoxicated:
He drank rye and water on the first night and became drunk. On the second night, he drank scotch and water and became drunk again. On the third night, he got drunk on bourbon and water. He therefore decided that the water was the cause of his getting drunk because it was the common element each time. (p. 76)
The problem here is that there is a second factor common to the different occasions on which he became intoxicated--the alcohol in the beverages the man is drinking. Because the man was unable to observe the alcoholin the beverages, however, he was unable to consider it as a possible cause. Thus, the inability to observe all common factors in a situation limits the usefulness of the method of agreement. The best that this method can do for us is to indicate possible causes that we then can investigate further with procedures that make use of the "method of difference."
Mill's Method of Difference
With the method of difference, one looks to see if changes in a phenomenon occur whenever a particular event changes. The single event that is found to change when differences occur in the phenomenon is said to be the cause. For example, in my dining room, whenever someonehas just pushed the wall switch up, the ceiling light turns on; and whenever someone has just pushed the switch down, the light turns off . If the position of the wall switch is the only event that changes in the two situations, then I probably will infer that the flipping of the switch up and down causes the ceiling light to turn on and off.
As another example, we can examine the research of Joseph Goldberger, an American physician of the nineteenth century, on the cause of pellagra. Pellagra is a disease characterized by "dizziness, lethargy, running sores, vomiting, and severe diarrhea" (Stanovich, 2001, p. 77). It had been noticed that the disease developed almost solely in people living in unsanitary conditions (such as the absence of indoor plumbing and sewer services). That is, one saw almost no cases in people living in sanitary conditions but a large number of cases in those living in unsanitary ones. If this were the only observable difference to be found between pellagra victims and those who didn't develop the disease, what is a possible cause of pellagra? Probably many of you thought of the possibility of a pellagra-causing "germ" (a bacterium or virus) that multiplies in unsanitary conditions. If so, your thinking is similar to that of many physicians of Goldberger's time.
Goldberger used the method of difference to test this "germ hypothesis" (a hypothesis is a speculative idea that is based on a set of observations): Goldberger, his wife, and a number of physicians working under him took part in what they called "filth parties" (Chase, 1980). At these "parties," the participants received bodily fluids taken from pellagra victims--bodily fluids that should contain any pellagra-causing germ. If they didn't have pellagra before receiving the bodily fluids, but did develop the disease after receiving the bodily fluids, then, based on the method of difference, it could be inferred that a germ causes pellagra. The participants in the study swallowed small dough balls filled with urine and feces, ingested scrapings from sores, and were injected with the blood of pellagra victims. None of them became ill even after engaging in a number of "filth parties." Thus, it seemed that pellagra is not caused by a germ.
If you think carefully about the initial finding of a relationship between sanitation and pellagra, you may see the error in thinking made by the pellagra researchers who initially concluded that a germ must cause the disease--an error in thinking that suggests a potential problem with using the method of difference to infer causation: there are other factors related to sanitation that also may have differed when comparing sanitary and unsanitary conditions. What are some of these factors? Here is a list of some possibilities:
Differences in any one of these factors--or in other factors related to them--may be the actual cause of pellagra. Thus, there is a major problem with using the method of difference to infer causation: there usuallyis a number of events that differ when the phenomenon under investigation differs. Any one of these events may cause changes in the phenomenon. In the pellagra example, poverty turned out to be a very important factor that researchers before Goldberger had neglected. Goldberger, who had grown up in a very poor family, used his experiences to develop the following hypothesis: very poor people are more likely to be malnourished; perhaps pellagra is caused by not eating the foods required for adequate nutrition. This is, in fact, what Goldberger found when he performed more observations based on the method of difference; but we'll come back to this in a later lesson.
To repeat, the fact that there typically is a number of events that differ from one situation to the next creates a major problem for the use of the method of difference. The additional fact that there often are limitations in our ability to observe all the differing factors makes the problem a very difficult one to solve in many cases. For example,in the pellagra case, most researchers were unable to observe the diets of poor people compared to those of wealthier people. Goldberger had observed such differences, but only because his family had been very poor when he was a boy. Thus, as was implied above when the method of agreement was discussed, researchers must make certain that they have carefully observed all possible factors (or, at least, taken their possible effects into account) when they are trying to make inferences about causation. In future lessons, the kinds of observations that work best for making such inferences will be described.
Critical Thinking Questions
Question 2-1
(a) In the textbook, there was a discussion of correlational studies in which it was stated that a "correlation exists when two variables are related to each other" (p. 14; a variable is anything that we can observe or measure that differs among individuals--such as height, IQ score, and level of anxiety). For example, the textbook mentioned that, for college students, there is a correlation between examination scores (Variable A) and the number of absences (Variable B): the more a student is absent, the less well that student does on examinations).
Which of Mill's methods does correlational research make use of? Can we infer the cause of the correlation between examination scores and number of absences? What is (are) the possible cause(s) of the correlation? (HINT: see Figure 1.7 in the textbook.) Please explain your answers to all three questions.
Suggested Answer
(b) In the textbook, there was a discussion of experimental studies. It was stated there that the "experiment is a research method in which the investigator manipulates one (independent) variable under carefully controlled conditions and observes whether any changes occur in a second (dependent) variable as a result" (p. 13). The independent varible can be thought of as the "causal variable": it is the one that we think is causing changes in the dependent variable. The dependent variable can be thought of as the "affected variable": it is the one that we think is being affected by changes in the independent variable. From the results of experiments, we are able to make conclusions about cause-and-effect relationships. For example, if you hypothesized that anxiety decreases examination scores, you would perform an experiment in which the participants' level of anxiety was manipulated and the effects of this manipulation on their examination scores was observed. If you found that those with higher levels of anxiety received lower scores, you would conclude that anxiety decreases examination scores.
Which of Mill's methods does experimental research make use of (please explain your answer)? Let's hypothesize that the number of absences is causally related to examination scores (that is, that a lower number of absences causes higher examination scores). Please outline an experiment designed to test this hypothesis. In your answer, please indicate the independent variable, the dependent variable, the experimental group, and the control group; and discuss all possible results and the interpretation you would make of each of these results.
Suggested Answer
Question 2-2
(a) Was Joseph Goldberger's study of the association of sanitation with pellagra an example of a correlational study or an experimental study? Please explain your answer. If you decide that the study was an experimental one, please indicate the independent variable, the dependent variable, the experimental group, and the control group.
Suggested Answer
(b) Was Joseph Goldberger's "filth parties" an example of a correlational study or an experimental study? Please explain your answer. If you decide that the study was an experimental one, please indicate the independent variable, the dependent variable, the experimental group, and the control group.
Suggested Answer
Question 2-3
The textbook discussed research on variables correlated with happiness (pages 17 through 21). Much of the research mentioned involved the use of surveys. A survey can be defined as a set of items designed to measure the beliefs, attitudes, motivations, emotions, etc., of a group of people. Happiness surveys include items designed to measure the level of happiness of people as well as any variables thought to be related to level of happiness. For example, one happiness survey included the following item:
Please check the one statement below that describes your average happiness.
[ ] 10 Extremely happy (feeling fantastic!)
[ ] 9 Very happy (feeling really good)
[ ] 8 Mildly happy (feeling fairly good and somewhat cheerful)
[ ] 7 Slightly happy (just a bit more than neutral)
[ ] 6 Neutral (not happy or unhappy)
[ ] 5 Slightly unhappy (just a bit below neutral)
[ ] 4 Mildly unhappy (just a little low)
[ ] 3 Pretty unhappy (somewhat "blue," spirits down)
[ ] 2 Very unhappy (depressed, spirits very low)
[ ] 1 Extremely unhappy (utterly depressed, completely down)
(a) If you were asked to respond to this item, which number would you choose? When making your choice, did you think of any possible problems with asking people to indicate their level of happiness in this way? Please describe the problem (or problems) that occurred to you.
Suggested Answer
(b) Use your answer to Question 2-3(a) to think critically about the data, presented on pages 17 and 19 of the textbook, comparing the average happiness levels of people from different countries around the world.
Suggested Answer
Bibliography and References
Baumeister, R. F. (1991). Meanings of life. New York: Guilford Press.
Chase, A. (1980). The legacy of Malthus: The social costs of the new scientific racism. Urbana: University of Illinois Press.
Christensen, L. B. (1994). Experimental methodology (6th ed.). Boston: Allyn and Bacon.
Goodwin, C. J. (1995). Research in psychology: Methods and design. New York: John Wiley & Sons, Inc.
Ricker, J. P. (2002). An introduction to the science of psychology. Boston: Pearson Custom Publishing.
Stanovich, K. E. (2001). How to think straight about psychology (6th ed.). New York: Longman.
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