Check Your Learning
Thinking Critically about Psychology
Correct Answers: 1.
freedom from coercion, informed consent, limited deception, adequate debriefi ng,
and confi dentiality (p. 40–41), 2. the research is necessary, the health of the animal is protected, pain
and suffering are minimized (p. 41–42)
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Design Your Own Formal Experiment
Now that we have gone over the basic principles of scientifi c research in psychology, it’s time for you to be the researcher.
After I suggest a research question, you will design a formal experiment to answer that question. To help you along, I will pose a series of questions. I hope this will be fun and give you a chance to review what you have just learned in a new con- text. Because books do not allow for much interaction between the author and the reader, I will guide you more than I would ordinarily do. I hope, however, that you will think about each question on your own before you read my suggested answers.
Here is the topic for your study: For a long time, psycholo- gists have thought that the simple act of telling someone about your private worries, disappointments, and agonies makes you feel better. In general, it often seems to help get negative feel- ings off your chest, whether you are venting your emotions to a friend, a relative, or a therapist. * More recently, psycholo- gists have suspected that expressing your negative emotions can even improve your physical health. So here is the gen- eral hypothesis for your study: Expressing negative emotions improves a person’s physical health over the next 6 months.
Who Will Your Research Participants Be? For the con- clusions of a study to be valid, a sample of subjects needs to be selected that is representative of some meaningful population of human beings. Because you are a student and have limited fi nancial resources for conducting this study, you probably are going to use introductory psychology students as your partici- pants. This means that you cannot be certain that your fi ndings apply to anyone other than introductory psychology students at similar schools. What should you do to ensure the represen- tativeness of your sample? For starters, select a sample that is typical in terms of the sex, age, race, and ethnic composition of college students in your school.
What Is the Independent Variable? You are designing a study to test the hypothesis that expressing negative emo- tions improves physical health, so the independent variable is whether or not a person expresses negative emotions. How could you arrange the conditions of this independent variable?
Take a moment to imagine how you would do it if you were really designing this formal experiment.
One reasonable experimental approach would be to ask half of the participants to express their feelings about the saddest thing that ever happened to them. This would be the experimental group, because the active condition of the inde- pendent variable is expressing negative feelings. The other half of the participants would be asked to describe the architecture of the buildings at their college. This would be the control group, because they do not express their negative emotions (unless the buildings at your school are really ugly). In this way, you could independently arrange for some participants to talk about their negative emotions and for other participants to talk about something else.
To protect everyone’s confi dentiality, you could ask all the participants to write a letter to someone they know. In this way, they could express their emotions (or describe the buildings) in a way that you do not hear. You could even ask them to destroy the letters at the end so there is no risk that your research participants would reveal some hidden feelings that they later wished they had kept private. The idea is to have half of the participants express their negative feelings, even if no one actually reads the letters. There are stronger ways of arranging this independent variable (you could actually have each person speak to a therapist a number of times), but writing this kind of letter can lead to some pretty intense emotional expression.
What Is the Dependent Variable? Your study will test the hypothesis that expressing negative emotions improves physical health, so the physical health of the participants is the dependent variable. If you ask the research participants to write the letters during the fall, you could measure their health over the next 6 months. How do you want to measure their physical health? That is, what will your operational defi nition of health be? Please think about it for a moment.
If you had a large research grant, you could draw blood samples every month and directly measure each participant’s immune system. Let’s assume that you are doing this study on a shoestring budget, however, and can ask the participants only each month if they have had a cold or the fl u during the past month. Then your quantitative dependent variable is the number of months in which each participant had a cold or the fl u. Now you can make your hypothesis more specifi c:
Writing a letter that expresses your emotions about the worst thing that had ever happened to you reduces your number of colds and the fl u over 6 months relative to persons who wrote a letter not on their emotions.
How Do You Decide Which Participants Will Be in the Experimental or Control Groups? Randomly! Remember that formal experiments allow valid conclusions only if the participants are randomly assigned to the different conditions of the independent variable. If you were to ask the students sitting in the front half of the classroom to express their nega- tive emotions and the students sitting in the back half of the classroom to write neutral letters, the two groups of students might differ in a systematic way. It is possible that students with better health tend to sit in the front (or the back). If so, this would invalidate your experiment, because the health of the participants in the experimental and the control groups would differ prior to the start of the study. Therefore, you will need to do something like assigning an identifi cation number to every participant and then using a computer to randomly assign each participant to one of the two groups.
What Kinds of Experimental Control Should You Use?
So far you have designed a formal experiment in which the participants will be randomly assigned to the conditions of the
* Of course, we always have to balance the benefi ts of expressing our negative feelings against the risks of hurting other people’s feelings and alienating ourselves from friends and family members. There is a right time and situation for almost everything.
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45 independent variable, and you have treated them all in the
same way, except for the independent variable. The only way in which your procedures are different for the two groups is that one group will write letters that will evoke negative emotions and the other group will write letters that should contain much less negative emotion. What else should you control to rule out alternative explanations for any differences between the groups? Consider that question for a moment.
Because you will ask the participants in the two groups to write letters about different topics, you cannot have both groups of participants in the same room at the same time. If you separate the groups and have them write their letters in different rooms, what should you control? Would it be okay to have a female research assistant give the instructions to the participants writing about their negative emotions while a male gives the instructions for the architecture letter in another room? Is it okay to have one group in a cheerful, well-lighted room and the other group in a cold, messy, dim room? If you treat the participants in the two groups differently in any way, you will not reach valid conclusions. Maybe the participants who wrote their letters in the cold, messy room caught colds while they were there!
Can You Make Your Study “Double Blind”? Recall what it means for a study to be double blind. In a double- blind experiment, neither the participants nor the researchers who measure the dependent variable know which participants received which condition of the independent variable. This is the same as saying that they do not know which participants were in the experimental or the control group. It would be an easy matter to keep the researchers who measure the depen- dent variable (ask the questions about having colds or the fl u, in this case) unaware of which participants were in the experi- mental and control groups.
It is not clear that you could keep the participants com- pletely unaware of who was in the experimental and the control groups. You would not tell them, of course, what your hypoth- esis is, but each participant would know if he or she wrote a letter about negative feelings or not. When you obtained
informed consent from the participants who volunteered for the study, you could tell them that you were studying the relationship between “communicating with others about dif- ferent topics through letters and physical health.” It is possible that some of the participants who wrote about their emotions would guess the hypothesis from this information. Why is that a problem? If the experimental group that wrote letters about negative emotions reported fewer colds and fl u over the next 6 months, that might be because the participants who guessed your hypothesis might intentionally or unintentionally tell you about fewer colds because they think that is what you want to hear. Alternatively, they might think your hypothesis is correct and intentionally or unintentionally remember fewer colds because they expect to be healthier. You would have to weigh this possibility carefully when interpreting your results and would need to continue thinking of better ways to control such alternative explanations in future experiments.
Formal Experiments Outside the Laboratory We have gone through this exercise both to review the logic and con- cepts of formal experiments that you have just learned and to give you the experience of thinking through the logic of an experiment yourself. Formal experiments are not something that only professional researchers can perform. You can use the powerful logic of formal experiments to answer questions in business, education, government, and other areas that affect human beings. For example, if you want to know which of two methods of manufacturing a product will create less pollution and fewer defective products, don’t guess —conduct a formal experiment. In the long run, it may be much wiser to compare the two methods in a formal experiment than to make a bad decision based on inadequate information. Similarly, it is not diffi cult for governments to conduct formal experiments that compare alternatives to housing the homeless, increasing the use of public transportation, or recycling waste. Formal experi- ments are just ways of using observation and critical thinking to answer important questions—and there are plenty of important questions in the real world that need good answers.
Chapter 2 describes the scientifi c methods that psychologists use to move beyond mere speculation about human behavior and mental processes.
I. The scientifi c method is to make systematic observations following rules for obtaining and using evidence to answer questions.
II. Psychologists use two major types of scientifi c methods to study human behavior and mental processes—descriptive methods and formal experiments.
A. Descriptive methods allow researchers to study people as they live their lives.
1. Surveys are a descriptive method that involves asking questions of groups of persons who are representative of the entire population.
2. Naturalistic observation involves unobtrusive observa- tions of behavior in real-life settings.
3. The clinical method involves observing people when they are receiving help from a mental health profes- sional for psychological problems.
4. Correlational methods are used to describe systematic relations between quantitatively measured variables in statistical terms.
Summary
a. The correlation coeffi cient provides a standard mathematical method of measuring the strength of the relationship between two variables.
b. Like other descriptive methods of research, the cor- relational method does not allow researchers to reach conclusions about cause-and-effect r elations between the variables studied. Correlation does not necessarily imply causation.
B. Formal experiments often can be used to reach conclu- sions about cause-and-effect relationships between variables.
1. In formal experiments, the independent variable is the one that the researcher independently arranges to see if different conditions of the independent variable have different effects on the dependent variable (usu- ally the behavior or mental processes of the partici- pants in the study).
2. Unlike descriptive methods of research, formal experi- ments involve arranging the conditions of the inde- pendent variable to study its effects on the depen- dent variable and carefully controlling other extrane- ous factors. In formal experiments, a key method of controlling alternative explanations for differences in the dependent variable is random assignment of par- ticipants to the various conditions of the independent variable (to reduce the likelihood that the participants in different groups do not differ from one another systematically in other ways).
3. In some types of experiments, placebo control is used to keep research participants unaware of which condi- tion of the independent variable they are receiving.
For example, in a study of a medication, half of the participants might receive a pill containing the active ingredient and half of the participants would receive a placebo pill that is identical in every way except it does not contain the active ingredient.
4. The most complete experimental control can be achieved in so-called double-blind experiments in which both the research participants and the research- ers who measure the dependent variable are unaware of the condition of the independent variable that each participant is receiving.
5. The simplest kind of formal experiment involves one experimental group, which receives the active
condition of the independent variable, and a control group, which receives none of the independent vari- able. The research can infer that differences between these groups on the dependent variable was likely caused by the independent variable when participants are randomly assigned to these two groups and strin- gent and complete experimental controls are used.
III. Statistics are used to describe the results of studies and to help researchers reach conclusions about their data.
A. Research findings on many participants can be sum- marized using the descriptive statistics of the mode, the mean, the median, and the standard deviation.
B. Tests of statistical significance are used (cautiously) to determine if correlations and differences between mean are large enough to be very unlikely to have been found by chance.
IV. Ethical research carefully protects the rights of participants in many ways.
A. Research using humans is considered to be ethical when the following conditions are met:
1. Individuals are asked to volunteer to participate with- out coercion.
2. Individuals are informed about the nature of the experiment before giving consent to participate.
3. Unnecessary deception of the participants is avoided, and deception is carefully regulated when required.
4. When deception is used, the true nature of the study is fully explained to the participant after the study is over.
5. All information learned about the participant is kept completely confidential.
B. Research involving nonhuman animals is considered ethi- cal when the following conditions are met:
1. The study is necessary to understand an important issue concerning behavior and mental processes.
2. The health of the animal subjects is protected.
3. The animals are treated humanely.
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chapter three
Biological foundations of behavior
Chapter Outline
PROLOGUE 47
Nervous System: Biological Control Center 48 Divisions of the Nervous System 56
Structures and Functions of the Brain 61 Human Diversity: Sex Differences in the Cerebral Cortex 73
Endocrine System: Chemical Messengers of the Body 77
Application of Psychology: “Madness” and the Brain 82
SUMMARY 86
VISUAL REVIEW OF BRAIN STRUCTURES 87
Prologue
Psychological life depends on biological life for its very existence. If humans did not have hands that grasp, we might never have learned to write, paint, or play racquetball. If we did not have eyes that could sense color, we would see a world that existed only in shades of black and white.
The brain is the part of the body most intimately linked to psy- chological life. A classic experiment conducted by Canadian brain surgeon Wilder Penfi eld in the 1930s dramatically illustrates this fact.
Dr. Penfi eld was conducting surgery on the surface layer of the brain known as the cerebral cortex while the patient was awake under local anesthesia. When Penfi eld placed a small rod that carried a mild elec- tric current against the brain, his patient experienced being in her
kitchen. In the background, she could hear the voice of her little boy playing in the yard and cars passing in the street. When another patient’s brain was stimulated he recalled a small-town baseball game that included a boy trying to crawl under a fence. Penfi eld’s experiment showed that the cerebral cor- tex is involved in our psychological experiences. This is just one of many ways in which we know that the brain and our psychological lives are intimately connected.
In this chapter, we discuss several aspects of human biology directly rel- evant to understanding behavior: the brain and nervous system, endocrine glands, and genetic mechanisms. We study these biological systems because we are psychological beings living in biological “machines.” Just as electronic machines are built from wires, transistors, and other components, the nervous system is built from specialized cells called neurons. Billions of neurons in your