As stated in previous sections, the kind of theory in which scientists are most interested is one that specifies the cause or causes of a phenomenon, such as why the sun appears to rise in the east and set in the west. But the question of what constitutes a cause is not as simple as you might think. Thus, in this section, I will describe what is meant by the term cause and how we will use this term in the rest of the course.

To begin the discussion, let's look at a case described by the neurologist, Oliver Sacks (1974), of a woman who, over the period of a few days, developed some very unusual symptoms:

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, it is claimed, anxiety due to unconscious psychological conflicts is transformed into sensory or movement problems]....

By 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 maladaptive psychological 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. Perhaps it had something to do with the antibiotics she 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" given that 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 problems, 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 this particular woman's symptoms; and perhaps could even cause them in others who are overly sensitive to their effects. But 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"?

Of course, at this point, you may be stating (perhaps with some annoyance), "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, such as the one described above. This is especially true when we consider the causes of nonphysical events such as thoughts and emotions. Let's examine some ideas that may help us to better understand what is meant by the word "cause" in psychology.

Sufficient Conditions

For most of us in our everyday lives, a cause is something that, if it occurs, then a particular effect occurs 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, if you state that a fire was caused by throwing a lit match into a wastebasket full of paper, you are implying that, any time a lit match is thrown into a wastebasket, a fire will develop. These two 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 occurrence of an 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 generally are very complex. For example, pressing the power button will not turn the television set on unless some other things also are true:

• 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. Thus, as you can see, a sufficient condition for turning on a television actually involves the co-occurrence of a number of other 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 or if there is no oxygen in the room. 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 the many additional factors that also must occur if a particular factor is to act as a cause of something else. In short, each factor contributes to the outcome, but none alone is sufficient for the effect to occur. A sufficient condition, therefore, is the set of factors that leads to a particular outcome.

Although you might think that the ultimate goal of research in psychology is to discover sufficient conditions for mental and behavioral phenomena, this is not always, and probably not even often, the case. Researchers typically have more modest goals (see below).

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 ("you can't win if you don't play"). 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 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. For example, alcohol will tend to cause a person to feel intoxicated, but only if that person drinks a certain amount. And the amount required will differ from one person to another based on their tolerance for alcohol (that is, if they drink frequently, they usually will need more to feel intoxicated), their height (if they are taller, they usually will need more), their metabolism (if their livers break down alcohol quickly, they usually will need more), and so on. As you can see, we can't claim that drinking will cause a person to feel intoxicated unless we take into account the effects of many factors.

In virtually all cases, the behaviors and mental events studied by psychologists are caused by a large number of interacting factors. Thus, we need to perform investigations of a number of these factors and their interactions before we can develop a comprehensive theory of a psychological phenomenon. For example, our present understanding of schizophrenia suggests that the disease is caused by many interacting factors, such as abnormal genes, viral infections, abnormal biochemical activity in the brain, psychosocial stress, and environmental toxins. Brown and Ghiselli (1955) stated that such theories are the norm in psychology:

The most consistent characteristic of human behavior is the complexity of its determinants[∂]. We must think of every behavior sequence as stemming from many determinants. Some of these initiate their influence at the time of the conception of the individual, others come into play just prior to the occurrence of the observed behavior, while numerous others arise in between these two extremes on the time axis. Behavioral processes do not function independently but interact with each other in many intricate and complex ways. Combinations of determinants act over various intervals: sometimes forming [developmental] series occupying hours, days, months, or years; at other times acting for merely a second or as a simultaneous flash occurrence." (pp. 70-71)

We refer to this idea as multifactorial causation, which means that a phenomenon is determined by many interacting factors. As Brown and Ghiselli suggested, the many factors that determine a phenomenon occur over the lifetimes of individuals. In the case of schizophrenia, there are distal factors (those that occurred some time ago) — such as viral infections during fetal development — and proximal factors (those that occurred recently) — such as stressful events (see Figure 3). The distal and proximal factors tend to interact in complex ways that can be very difficult to investigate.

Insert Fig 3 Here
Figure 3. Distal and Proximal Factors Involved in the
Multifactorial Causation of a Phenemenon.

Let's look at an example. Does smoking cause cancer? Yes, it does, but not every person who smokes will develop cancer: he or she has only an increased chance of developing cancer. Why does smoking only increase a person's chances of developing lung cancer? Why does smoking not guarantee that a person will develop lung cancer (that is, why is smoking not a sufficient cause of lung cancer)? It probably occurred to you that there are other factors that increase or decrease the harmful effects of smoking. For example, genes, diet, amount of exercise, stress levels, amount of alcohol consumed, and so on, are factors that may interact with smoking in determining who will and who will not develop lung cancer.

Furthermore, why can nonsmokers develop lung cancer (that is, why is smoking not a necessary cause of lung cancer)? Again, other factors, such as genes, diet, alcohol, etc., are thought to influence the development of lung cancer. Each factor, when looked at individually, increases the chance of developing lung cancer, but probably none alone is sufficient to cause lung cancer. It seems very likely that the causes of lung cancer are many and that their interactions are complex.

Thus, in this course, we will define a cause as a factor that increases or decreases the probability that a particular outcome (event) will occur. Whether or not the event actually occurs depends on whether or not a set of interacting causes occurring over time is a sufficient condition for the event's occurrence. Furthermore, the event's occurrence depends on the effects of distal causes — factors that acted a long time ago (with respect to an individual's lifetime or evolutionary time) — and proximal causes — factors that acted close in time to the event's occurrence.

Study Questions for Section 1-6

1. How would you define a sufficient condition in your own words?
2. What is an example of a sufficient condition not mentioned above?
3. How would you define a necessary condition in your own words?
4. What is an example of a necessary condition not mentioned above?
5. When developing theories, are researchers trying to find necessary conditions? Are they trying to find sufficient conditions?
6. What is an example of a psychological cause that you have learned so far in this course?
7. How would you define the concept of "multifactorial causation" in your own words?
8. What is an example of multifactorial causation from your everyday experience?
9. How would you define a distal factor in your own words?
10. What is an example of a distal factor?
11. How would you define a proximal factor in your own words?
12. What is an example of a proximal factor?
13. How are defining the word "cause" in this course?

Go to Quiz 1-6 questions

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