SELECTING RESEARCH PARTICIPANTS ASSIGNMENT

SELECTING RESEARCH PARTICIPANTS ASSIGNMENT

SELECTING RESEARCH PARTICIPANTS ASSIGNMENT

The focus of your study may be children, college students, elderly adults, employees, rats, pigeons, or even cockroaches or flatworms; in all cases, the participants or subjects must somehow be selected. The method used to select participants can have a profound impact on external validity. Remember that external validity is defined as the extent to which results from a study can be generalized to other populations and settings.

Most research projects involve sampling research participants from a population of interest. The population is composed of all of the individuals of interest to the researcher. Samples may be drawn from the population using probability sampling or nonprobability sampling techniques. When it is important to accurately describe the population, you must use probability sampling. This is why probability sampling is so crucial when conducting scientific polls. Much research, on the other hand, is more interested in testing hypotheses about behavior: attempting to detect whether X causes Yrather than describing a population. Here, the two focuses of the study are the relationships between the variables being studied and tests of predictions derived from theories of behavior. In such cases, the participants may be found in the easiest way possible using nonprobability sampling methods, also known as haphazard or “convenience” methods. You may ask students in introductory psychology classes to participate, knock on doors in your dorm to find people to be tested, or choose a class in which to test children simply because you know the teacher. Nothing is wrong with such methods as long as you recognize that they affect the ability to generalize your results to some larger population. In Chapter 14, we examine the issues of generalizing from the rather atypical samples of college students and other conveniently obtained research participants. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

You will also need to determine your sample size. How many participants will you need in your study? In general, increasing your sample size increases the likelihood that your results will be statistically significant, because larger samples provide more accurate estimates of population values (see Table 7.2, p. 149). Most researchers take note of the sample sizes in the research area being studied and select a sample size that is typical for studies in the area. A more formal approach to selecting a sample size, called power analysis, is discussed in Chapter 13.

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MANIPULATING THE INDEPENDENT VARIABLE

To manipulate an independent variable, you have to construct an operational definition of the variable (see Chapter 4). That is, you must turn a conceptual variable into a set of operations—specific instructions, events, and stimuli to be presented to the research participants. The manipulation of the independent variable, then, is when a researcher changes the conditions to which participants are exposed. In addition, the independent and dependent variables must be introduced within the context of the total experimental setting. This has been called setting the stage (Aronson, Brewer, & Carlsmith, 1985). SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Setting the Stage

In setting the stage, you usually have to supply the participants with the information necessary for them to provide their informed consent to participate (informed consent is covered in Chapter 3). This generally includes information about the underlying rationale of the study. Sometimes, the rationale given is completely truthful, although only rarely will you want to tell participants the actual hypothesis. For example, you might say that you are conducting an experiment on memory when, in fact, you are studying a specific aspect of memory (your independent variable). If participants know what you are studying, they may try to confirm (or even deny) the hypothesis, or they may try to look good by behaving in the most socially acceptable way. If you find that deception is necessary, you have a special obligation to address the deception when you debrief the participants at the conclusion of the experiment.

There are no clear-cut rules for setting the stage, except that the experimental setting must seem plausible to the participants, nor are there any clear-cut rules for translating conceptual variables into specific operations. Exactly how the variable is manipulated depends on the variable and the cost, practicality, and ethics of the procedures being considered.

Types of Manipulations

Straightforward manipulations Researchers are usually able to manipulate an independent variable with relative simplicity by presenting written, verbal, or visual material to the participants. Such straightforward manipulations manipulate variables with instructions and stimulus presentations. Stimuli may be presented verbally, in written form, via videotape, or with a computer. Let’s look at a few examples. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Goldstein, Cialdini, and Griskevicius (2008) were interested in the influence of signs that hotels leave in their bathrooms encouraging guests to reuse their towels. In their research, they simply printed signs that were hooked on towel shelves in the rooms of single guests staying at least two nights. In a standard message, the sign read “HELP SAVE THE ENVIRONMENT. You can show your respect of nature and help save the environment by reusing Page 182towels during your stay.” In this case, 35% of the guests reused their towels on the second day. Another condition invoked a social norm that other people are reusing towels: “JOIN YOUR FELLOW GUESTS IN HELPING TO SAVE THE ENVIRONMENT. Almost 75% of guests who are asked to participate in our new resource savings program do help by using their towels more than once. You can join your fellow guests in this program to save the environment by reusing your towels during your stay.” This sign resulted in 44% reusing their towels. As you might expect, the researchers have extended this research to study ways that the sign can be even more effective in increasing conservation.

Most memory research relies on straightforward manipulations. For example, Coltheart and Langdon (1998) displayed lists of words to participants and later measured recall. The word lists differed on phonological similarity: Some lists had words that sounded similar, such as cat, map, and pat, and other lists had dissimilar words such as mop, pen, and cow. They found that lists with dissimilar words are recalled more accurately. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Educational programs are most often straightforward. Pawlenko, Safer, Wise, and Holfeld (2013) examined the effectiveness of three training programs designed to improve jurors’ ability to evaluate eyewitness testimony. Subjects viewed one of three 15-minute slide presentations on a computer screen. The Interview-Identification-Eyewitness training focused on three steps to analyze eyewitness evidence: Ask if the eyewitness interviews were done properly, ask if identification methods were proper, and evaluate if the conditions of the crime scene allowed for an accurate identification. A second presentation termed “Biggers training” was a presentation of five eyewitness factors that the Supreme Court determined should be used (developed in a case called Neil v. Biggers). The Jury Duty presentation was a summary of standard information provided to jurors such as the need to be fair and impartial and the importance of hearing all evidence before reaching a verdict. After viewing the presentations, subjects read a trial transcript that included problems with the eyewitness identification procedures. The subjects in the Interview-Identification-Eyewitness conditions were most likely to use these problems in reaching a verdict.

As a final example of a straightforward manipulation, consider a study by Mazer, Murphy, and Simonds (2009) on the effect of college teacher self-disclosure (via Facebook) on perceptions of teacher effectiveness. For this study, students read one of three Facebook profiles that were created for a volunteer teacher, one for each of the high-, medium-, and low-disclosure conditions. Level of disclosure was manipulated by changing the number and nature of photographs, biographical information, favorite movies/books/quotes, campus groups, and posts on “the wall.” After viewing the profile to which they were assigned, participants rated the teacher on several dimensions. Higher disclosure resulted in perceptions of greater caring and trustworthiness; however, disclosure was not related to perceptions of teacher competence. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

You will find that most manipulations of independent variables in all areas of research are straightforward. Researchers vary the difficulty of material to Page 183be learned, motivation levels, the way questions are asked, characteristics of people to be judged, and a variety of other factors in a straightforward manner.

Staged manipulations Other manipulations are less straightforward. Sometimes, it is necessary to stage events during the experiment in order to manipulate the independent variable successfully. When this occurs, the manipulation is called a staged manipulation or event manipulation. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Staged manipulations are most frequently used for two reasons. First, the researcher may be trying to create some psychological state in the participants, such as frustration, anger, or a temporary lowering of self-esteem. For example, Zitek and her colleagues studied what is termed a sense of entitlement (Zitek, Jordan, Monin, & Leach, 2010). Their hypothesis is that the feeling of being unfairly wronged leads to a sense of entitlement and, as a result, the tendency to be more selfish with others. In their study, all participants played a computer game. The researchers programmed the game so that some participants would lose when the game crashed. This is an unfair outcome, because the participants lost for no good reason. Participants in the other condition also lost, but they thought it was because the game itself was very difficult. The participants experiencing the broken game did in fact behave more selfishly after the game; they later allocated themselves more money than deserved when competing with another participant.

Second, a staged manipulation may be necessary to simulate some situation that occurs in the real world. Recall the Milgram obedience experiment that was described in Chapter 3. In that study, an elaborate procedure—ostensibly to study learning—was constructed to actually study obedience to an authority. Or consider a study on computer multitasking conducted by Bowman, Levine, Waite, and Gendron (2010), wherein students read academic material presented on a computer screen. In one condition, the participants received and responded to instant messages while they were reading. Other participants did not receive any messages. Student performance on a test was equal in the two conditions. However, students in the instant message condition took longer to read the material (after the time spent on the message was subtracted from the total time working on the computer). SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Staged manipulations frequently employ a confederate (sometimes termed an “accomplice”). Usually, the confederate appears to be another participant in an experiment but is actually part of the manipulation (we discussed the use of confederates in Chapter 3). A confederate may be useful to create a particular social situation. For example, Hermans, Herman, Larsen, and Engels (2010) studied whether food intake by males is affected by the amount of food consumed by a companion. Participants were recruited for a study on evaluation of movie trailers. The participant and a confederate sat in a comfortable setting in which they viewed and evaluated three trailers. They were then told that they needed a break before viewing the next trailers; snacks were available if they were interested. In one condition, the confederate took a large serving of snacks. A small serving was taken in another condition, and the confederate Page 184did not eat in the third condition. The researchers then measured the amount consumed by the actual participants; they did model the amount consumed by the confederate but only when they were hungry.

FIGURE 9.1

Example of the Asch line judgment task

The classic Asch (1956) conformity experiment provides another example of how confederates may be used. Asch gathered people into groups and asked them to respond to a line judgment task such as the one in Figure 9.1. Which of the three test lines matches the standard? Although this appears to be a simple task, Asch made it more interesting by having several confederates announce the same incorrect judgment prior to asking the actual participant; this procedure was repeated over a number of trials with different line judgments. Asch was able to demonstrate how easy it is to produce conformity—participants conformed to the unanimous majority on many of the trials even though the correct answer was clear. Finally, confederates may be used in field experiments as well as laboratory research. As described in Chapter 4, Lee, Schwarz, Taubman, and Hou (2010) studied the impact of public sneezing on the perception of unrelated risks by having an accomplice either sneeze or not sneeze (control condition) while walking by someone in a public area of a university. A researcher then approached those people with a request to complete a questionnaire, which they described as a “class project.” The questionnaire measured participants’ perceptions of average Americans’ risk of contracting a serious disease. The researchers found that, indeed, being around a person who sneezes increases self-reported perception of risk. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

As you can see, staged manipulations demand a great deal of ingenuity and even some acting ability. They are used to involve the participants in an ongoing social situation that the individuals perceive not as an experiment but as a real experience. Researchers assume that the result will be natural behavior that truly reflects the feelings and intentions of the participants. However, such procedures allow for a great deal of subtle interpersonal communication that is hard to put into words; this may make it difficult for other researchers to replicate the experiment. Also, a complex manipulation is difficult to interpret. If many things happened during the experiment, what one thing was responsible for the results? In general, it is easier to interpret results when the manipulation is relatively straightforward. However, the nature of the variable you are studying sometimes demands complicated procedures.

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Strength of the Manipulation

The simplest experimental design has two levels of the independent variable. In planning the experiment, the researcher has to choose these levels. A general principle to follow is to make the manipulation as strong as possible. A strong manipulation maximizes the differences between the two groups and increases the chances that the independent variable will have a statistically significant effect on the dependent variable. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

To illustrate, suppose you think that there is a positive linear relationship between attitude similarity and liking (“birds of a feather flock together”). In conducting the experiment, you could arrange for participants to encounter another person, a confederate. In one group, the confederate and the participant would share similar attitudes; in the other group, the confederate and the participant would be dissimilar. Similarity, then, is the independent variable, and liking is the dependent variable. Now you have to decide on the amount of similarity. Figure 9.2 shows the hypothesized relationship between attitude similarity and liking at 10 different levels of similarity. Level 1 represents the least amount of similarity with no common attitudes, and level 10 the greatest (all attitudes are similar). To achieve the strongest manipulation, the participants in one group would encounter a confederate of level 1 similarity; those in the other group would encounter a confederate of level 10 similarity. This would result in the greatest difference in the liking means—a 9-point difference. A weaker manipulation—using levels 4 and 7, for example—would result in a smaller mean difference.

A strong manipulation is particularly important in the early stages of research, when the researcher is most interested in demonstrating that a relationship does, in fact, exist. If the early experiments reveal a relationship between the variables, subsequent research can systematically manipulate the other levels of the independent variable to provide a more detailed picture of the relationship. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

FIGURE 9.2

Relationship between attitude similarity and liking

Page 186The principle of using the strongest manipulation possible should be tempered by at least two considerations. The first concerns the external validity of a study: The strongest possible manipulation may entail a situation that rarely, if ever, occurs in the real world. For example, an extremely strong crowding manipulation might involve placing so many people in a room that no one could move—a manipulation that might significantly affect a variety of behaviors. However, we would not know if the results were similar to those occurring in more common, less crowded situations, such as many classrooms or offices.

A second consideration is ethics: A manipulation should be as strong as possible within the bounds of ethics. A strong manipulation of fear or anxiety, for example, might not be possible because of the potential physical and psychological harm to participants. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Cost of the Manipulation

Cost is another factor in the decision about how to manipulate the independent variable. Researchers who have limited monetary resources may not be able to afford expensive equipment, salaries for confederates, or payments to participants in long-term experiments. Also, a manipulation in which participants must be run individually requires more of the researcher’s time than a manipulation that allows running many individuals in a single setting. In this respect, a manipulation that uses straightforward presentation of written or verbal material is less costly than a complex, staged experimental manipulation. Some government and private agencies offer grants for research; because much research is costly, continued public support of these agencies is very important.

MEASURING THE DEPENDENT VARIABLE

In previous chapters, we have discussed various aspects of measuring variables, including reliability, validity, and reactivity of measures; observational methods; and the development of self-report measures for questionnaires and interviews. In this section, we will focus on measurement considerations that are particularly relevant to experimental research. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Types of Measures

The dependent variable in most experiments is one of three general types: self-report, behavioral, or physiological.

Self-report measures Self-reports can be used to measure attitudes, liking for someone, judgments about someone’s personality characteristics, intended behaviors, emotional states, attributions about why someone performed well or poorly on a task, confidence in one’s judgments, and many other aspects of human thought and behavior. Rating scales with descriptive anchors Page 187(endpoints) are most commonly used. For example, Funk and Todorov (2013) studied the impact of a facial tattoo on impressions of a man accused of assault. The man, Jack, had punched another man in a bar following a dispute over a spilled drink. A description of the incident included a photo of Jack with or without a facial tattoo. After viewing the photo and reading the description, subjects responded to several questions on a 7-point scale that included the following:

How likely is it that Jack is guilty?

Behavioral measures Behavioral measures are direct observations of behaviors. As with self-reports, measurements of an almost endless number of behaviors are possible. Sometimes, the researcher may record whether a given behavior occurs—for example, whether an individual responds to a request for help, makes an error on a test, or chooses to engage in one activity rather than another. Often, the researcher must decide whether to record the number of times a behavior occurs in a given time period—the rate of a behavior; how quickly a response occurs after a stimulus—a reaction time; or how long a behavior lasts—a measure of duration. The decision about which aspect of behavior to measure depends on which is most theoretically relevant for the study of a particular problem or which measure logically follows from the independent variable manipulation. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

As an example, consider a study on eating behavior while viewing a food-related or nature television program (Bodenlos & Wormuth, 2013). Participants had access to chocolate-covered candies, cheese curls, and carrots that were weighed before and after the session. More candy was consumed during the food-related program; there were no differences for the other two foods.

Sometimes the behavioral measure is not an actual behavior but a behavioral intention or choice. Recall the study described in Chapter 3 in which subjects decided how much hot sauce another subject would have to consume later in the study (Vasquez, Pederson, Bushman, Kelley, Demeestere, & Miller, 2013). They did not actually pour the hot sauce but they did commit to an action rather than simply indicate their feelings about the other subject. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Physiological measures Physiological measures are recordings of responses of the body. Many such measurements are available; examples include the galvanic skin response (GSR), electromyogram (EMG), and electroencephalogram (EEG). The GSR is a measure of general emotional arousal and anxiety; it measures the electrical conductance of the skin, which changes when sweating occurs. The EMG measures muscle tension and is frequently used as a measure of tension or stress. The EEG is a measure of electrical activity of brain cells. It can be used to record general brain arousal as a response to different situations, such as activity in certain parts of the brain as learning occurs or brain activity during different stages of sleep.

Page 188The GSR, EMG, and EEG have long been used as physiological indicators of important psychological variables. Many other physiological measures are available, including temperature, heart rate, and analysis of blood or urine (see Cacioppo & Tassinary, 1990). In recent years, magnetic resonance imaging (MRI) has become an increasingly important tool for researchers in behavioral neuroscience. An MRI provides an image of an individual’s brain structure. It allows scientists to compare the brain structure of individuals with a particular condition (e.g., a cognitive impairment, schizophrenia, or attention deficit hyperactivity disorder) with the brain structure of people without the condition. In addition, a functional MRI (fMRI) allows researchers to scan areas of the brain while a research participant performs a physical or cognitive task. The data provide evidence for what brain processes are involved in these tasks. For example, a researcher can see which areas of the brain are most active when performing different memory tasks. In one study using fMRI, elderly adults with higher levels of education not only performed better on memory tasks than their less educated peers, but they also used areas of their frontal cortex that were not used by other elderly and younger individuals (Springer, McIntosh, Winocur, & Grady, 2005). SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Multiple Measures

Although it is convenient to describe single dependent variables, most studies include more than one dependent measure. One reason to use multiple measures stems from the fact that a variable can be measured in a variety of concrete ways (recall the discussion of operational definitions in Chapter 4). In a study on the effects of an employee wellness program on health, the researchers might measure self-reported fatigue, stress, physical activity, and eating habits along with physical measures of blood pressure, blood sugar, cholesterol, and weight (cf. Clark et al, 2011). If the independent variable has the same effect on several measures of the same dependent variable, our confidence in the results is increased. It is also useful to know whether the same independent variable affects some measures but not others. For example, an independent variable designed to affect liking might have an effect on some measures of liking (e.g., desirability as a person to work with) but not others (e.g., desirability as a dating partner). Researchers may also be interested in studying the effects of an independent variable on several different behaviors. For example, an experiment on the effects of a new classroom management technique might examine academic performance, interaction rates among classmates, and teacher satisfaction.

When you have more than one dependent measure, the question of order arises. Does it matter which measures are made first? Is it possible that the results for a particular measure will be different if the measure comes earlier rather than later? The issue is similar to the order effects that were discussed in Chapter 8 in the context of repeated measures designs. Perhaps responding to the first measures will somehow affect responses on the later measures, Page 189or perhaps the participants attend more closely to first measures than to later measures. There are two possible ways of responding to this issue. If it appears that the problem is serious, the order of presenting the measures can be counterbalanced using the techniques described in Chapter 8. Often there are no indications from previous research that order is a serious problem. In this case, the prudent response is to present the most important measures first and the less important ones later. With this approach, order will not be a problem in interpreting the results on the most important dependent variables. Even though order may be a potential problem for some of the measures, the overall impact on the study is minimized. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Making multiple measurements in a single experiment is valuable when it is feasible to do so. However, it may be necessary to conduct a separate series of experiments to explore the effects of an independent variable on various behaviors.

Sensitivity of the Dependent Variable

The dependent variable should be sensitive enough to detect differences between groups. A measure of liking that asks, “Do you like this person?” with only a simple “yes” or “no” response alternative is less sensitive than one that asks, “How much do you like this person?” on a 5- or 7-point scale. With the first measure, people may tend to be nice and say yes even if they have some negative feelings about the person. The second measure allows for a gradation of liking; such a scale would make it easier to detect differences in amount of liking. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

The issue of sensitivity is particularly important when measuring human performance. Memory can be measured using recall, recognition, or reaction time; cognitive task performance might be measured by examining speed or number of errors during a proofreading task; physical performance can be measured through various motor tasks. Such tasks vary in their difficulty. Sometimes a task is so easy that everyone does well regardless of the conditions that are manipulated by the independent variable. This results in what is called a ceiling effect—the independent variable appears to have no effect on the dependent measure only because participants quickly reach the maximum performance level. The opposite problem occurs when a task is so difficult that hardly anyone can perform well; this is called a floor effect.

The need to consider sensitivity of measures is nicely illustrated in the Freedman et al. (1971) study of crowding mentioned in Chapter 4. The study examined the effect of crowding on various measures of cognitive task performance and found that crowding did not impair performance. You could conclude that crowding has no effect on performance; however, it is also possible that the measures were either too easy or too difficult to detect an effect of crowding. In fact, subsequent research showed that the tasks may have been too easy; when subjects perform complex cognitive tasks in laboratory or natural settings, crowding does result in lower performance (Bruins & Barber, 2000; Paulus, Annis, Seta, Schkade, & Matthews, 1976). SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

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Cost of Measures

Another consideration is cost—some measures may be more costly than others. Paper-and-pencil self-report measures are generally inexpensive; measures that require trained observers or elaborate equipment can become quite costly. A researcher studying nonverbal behavior, for example, might have to use a video camera to record each participant’s behaviors in a situation. Two or more observers would then have to view the tapes to code behaviors such as eye contact, smiling, or self-touching (two observers are needed to ensure that the observations are reliable). Thus, there would be expenses for both equipment and personnel. Physiological recording devices are also expensive. Researchers need resources from the university or outside agencies to carry out such research.

ADDITIONAL CONTROLS

The basic experimental design has two groups: in the simplest case, an experimental group that receives the treatment and a control group that does not. Use of a control group makes it possible to eliminate a variety of alternative explanations for the results, thus improving internal validity. Sometimes additional control procedures may be necessary to address other types of alternative explanations. Two general control issues concern expectancies on the part of both the participants in the experiment and the experimenters. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Controlling for Participant Expectations

Demand characteristics We noted previously that experimenters generally do not wish to inform participants about the specific hypotheses being studied or the exact purpose of the research. The reason for this lies in the problem of demand characteristics (Orne, 1962), which is any feature of an experiment that might inform participants of the purpose of the study. The concern is that when participants form expectations about the hypothesis of the study, they will then do whatever is necessary to confirm the hypothesis. For example, if you were studying the relationship between political orientation and homophobia, participants might figure out the hypothesis and behave according to what they think you want, rather than according to their true selves.

One way to control for demand characteristics is to use deception—to make participants think that the experiment is studying one thing when actually it is studying something else. The experimenter may devise elaborate cover stories to explain the purpose of the study and to disguise what is really being studied. The researcher may also attempt to disguise the dependent variable by using an unobtrusive measure or by placing the measure among a set of unrelated filler items on a questionnaire. Another approach is simply to assess whether demand characteristics are a problem by asking participants about their perceptions of the purpose of the research. It may be that participants do Page 191not have an accurate view of the purpose of the study; or if some individuals do guess the hypotheses of the study, their data may be analyzed separately.

Demand characteristics may be eliminated when people are not aware that an experiment is taking place or that their behavior is being observed. Thus, experiments conducted in field settings and observational research in which the observer is concealed or unobtrusive measures are used minimize the problem of demand characteristics.

Placebo groups A special kind of participant expectation arises in research on the effects of drugs. Consider an experiment that is investigating whether a drug such as Prozac reduces depression. One group of people diagnosed as depressive receives the drug and the other group receives nothing. Now suppose that the drug group shows an improvement. We do not know whether the improvement was caused by the properties of the drug or by the participants’ expectations about the effect of the drug—what is called a placebo effect. In other words, just administering a pill or an injection may be sufficient to cause an observed improvement in behavior. To control for this possibility, a placebo group can be added. Participants in the placebo group receive a pill or injection containing an inert, harmless substance; they do not receive the drug given to members of the experimental group. If the improvement results from the active properties of the drug, the participants in the experimental group should show greater improvement than those in the placebo group. If the placebo group improves as much as the experimental group, all improvement could be caused by a placebo effect.

Sometimes, participants’ expectations are the primary focus of an investigation. For example, Marlatt and Rohsenow (1980) conducted research to determine which behavioral effects of alcohol are due to alcohol itself as opposed to the psychological impact of believing one is drinking alcohol. The experimental design to examine these effects had four groups: (1) expect no alcohol–receive no alcohol, (2) expect no alcohol–receive alcohol, (3) expect alcohol–receive no alcohol, and (4) expect alcohol–receive alcohol. This design is called a balanced placebo design. Marlatt and Rohsenow’s research suggests that the belief that one has consumed alcohol is a more important determinant of behavior than the alcohol itself. That is, people who believed they had consumed alcohol (Groups 3 and 4) behaved very similarly, although those in Group 3 were not actually given any alcohol.

In some areas of research, the use of placebo control groups has ethical implications. Suppose you are studying a treatment that does have a positive effect on people (for example, by reducing migraine headaches or alleviating symptoms of depression). It is important to use careful experimental procedures to make sure that the treatment does have an impact and that alternative explanations for the effect, including a placebo effect, are eliminated. However, it is also important to help those people who are in the control conditions; this aligns with the concept of beneficence that was covered in Chapter 3. Thus, participants in the control conditions must be given the treatment as soon as Page 192they have completed their part in the study in order to maximize the benefits of participation.

Placebo effects are real and must receive serious study in many areas of research. A great deal of current research and debate focuses on the extent to which any beneficial effects of antidepressant medications such as Prozac are due to placebo effects (e.g., Kirsch, 2010; Wampold, Minami, Tierney, Baskin, & Bhati, 2005).

Controlling for Experimenter Expectations

Experimenters are usually aware of the purpose of the study and thus may develop expectations about how participants should respond. These expectations can in turn bias the results. This general problem is called experimenter bias or expectancy effects (Rosenthal, 1966, 1967, 1969).

Expectancy effects may occur whenever the experimenter knows which condition the participants are in. There are two potential sources of experimenter bias. First, the experimenter might unintentionally treat participants differently in the various conditions of the study. For example, certain words might be emphasized when reading instructions to one group but not the other, or the experimenter might smile more when interacting with people in one of the conditions. The second source of bias can occur when experimenters record the behaviors of the participants; there may be subtle differences in the way the experimenter interprets and records the behaviors.

Research on expectancy effects Expectancy effects have been studied in a variety of ways. Perhaps the earliest demonstration of the problem is the case of Clever Hans, a horse with alleged mathematical and other abilities that attracted the attention of Europeans in the early 20th century (Rosenthal, 1967). The owner of the horse posed questions to Hans who in turn would provide answers by tapping his hoof (e.g., a question of “what is two times five” would be followed by ten taps). Pfungst (1911) later showed that Hans was actually responding to barely detectable cues provided by the person asking the question. The person would look at the hoof as Hans started to tap and then changed to look at Hans as the correct answer was about to be given. Hans was responding to these head and eye movements that went undetected by observers.

If a clever horse can respond to subtle cues, it is reasonable to suppose that clever humans can too. In fact, research has shown that experimenter expectancies can be communicated to humans by both verbal and nonverbal means (Duncan, Rosenberg, & Finklestein, 1969; Jones & Cooper, 1971). An example of more systematic research on expectancy effects is a study by Rosenthal (1966). In this experiment, graduate students trained rats that were described as coming from either “maze bright” or “maze dull” genetic strains. The animals actually came from the same strain and had been randomly assigned to the bright and dull categories; however, the “bright” rats did perform better than the “dull” rats. Subtle differences in the ways the students treated the rats Page 193or recorded their behavior must have caused this result. A generalization of this particular finding is called “teacher expectancy.” Research has shown that telling a teacher that a pupil will bloom intellectually over the next year results in an increase in the pupil’s IQ score (Rosenthal & Jacobson, 1968). In short, teachers’ expectations can influence students’ performance.

The problem of expectations influencing ratings of behavior is nicely illustrated in an experiment by Langer and Abelson (1974). Clinical psychologists were shown a videotape of an interview in which the person interviewed was described as either an applicant for a job or a patient; in reality, all saw the same tape. The psychologists later rated the person as more “disturbed” when they thought the person was a patient than when the person was described as a job applicant.

Solutions to the expectancy problem Clearly, experimenter expectations can influence the outcomes of research investigations. How can this problem be solved? Fortunately, there are a number of ways to minimize expectancy effects. First, experimenters should be well trained and should practice behaving consistently with all participants. The benefit of training was illustrated in the Langer and Abelson study with clinical psychologists. The bias of rating the “patient” as disturbed was much less among behavior-oriented therapists than among traditional ones. Presumably, the training of the behavior-oriented therapists led them to focus more on the actual behavior of the person, so they were less influenced by expectations stemming from the label of “patient.”

Another solution is to run all conditions simultaneously so that the experimenter’s behavior is the same for all participants. This solution is feasible only under certain circumstances, however, such as when the study can be carried out with the use of printed materials or the experimenter’s instructions to participants are the same for everyone.

Expectancy effects are also minimized when the procedures are automated. As noted previously, it may be possible to manipulate independent variables and record responses using computers; with automated procedures, the experimenter’s expectations are less likely to influence the results.

A final solution is to use experimenters who are unaware of the hypothesis being investigated. In these cases, the person conducting the study or making observations is blind regarding what is being studied or which condition the participant is in. This procedure originated in drug research using placebo groups. In a single-blind experiment, the participant is unaware of whether a placebo or the actual drug is being administered; in a double-blind experiment, neither the participant nor the experimenter knows whether the placebo or actual treatment is being given. To use a procedure in which the experimenter or observer is unaware of either the hypothesis or the group the participant is in, you must hire other people to conduct the experiment and make observations.

Because researchers are aware of the problem of expectancy effects, solutions such as the ones just described are usually incorporated into the procedures of the study. The procedures used in scientific research must be precisely Page 194defined so they can be replicated by others. This allows other researchers to build on previous research. If a study does have a potential problem of expectancy effects, researchers are bound to notice and will attempt to replicate the experiment with procedures that control for them. It is also a self-correcting mechanism that ensures that methodological flaws will be discovered. The importance of replication will be discussed further in Chapter 14.

ADDITIONAL CONSIDERATIONS

So far, we have discussed several of the factors that a researcher considers when planning a study. Actually conducting the study and analyzing the results is a time-consuming process. Before beginning the research, the investigator wants to be as sure as possible that everything will be done right. And once the study has been designed, there are some additional procedures that will improve it.

Research Proposals

After putting considerable thought into planning the study, the researcher writes a research proposal. The proposal will include a literature review that provides a background for the study. The intent is to clearly explain why the research is being done—what questions the research is designed to answer. The details of the procedures that will be used to test the idea are then given. The plans for analysis of the data are also provided. A research proposal is very similar to the introduction and method sections of a journal article. Such proposals must be included in applications for research grants; ethics review committees require some type of proposal as well (see Chapter 3 for more information on Institutional Review Boards).

Preparing a proposal is a good idea in planning any research project because simply putting your thoughts on paper helps organize and systematize ideas. In addition, you can show the proposal to friends, colleagues, professors, and other interested parties who can provide useful feedback about the adequacy of your procedures. They may see problems that you did not recognize, or they may offer ways of improving the study.

Pilot Studies

When the researcher has finally decided on all the specific aspects of the procedure, it is possible to conduct a pilot study in which the researcher does a trial run with a small number of participants. The pilot study will reveal whether participants understand the instructions, whether the total experimental setting seems plausible, whether any confusing questions are being asked, and so on.

Sometimes participants in the pilot study are questioned in detail about the experience following the experiment. Another method is to use the think aloud protocol (described in Chapter 7) in which the participants in the pilot study Page 195are instructed to verbalize their thoughts about everything that is happening during the study. Such procedures provide the researcher with an opportunity to make any necessary changes in the procedure before doing the entire study. Also, a pilot study allows the experimenters who are collecting the data to become comfortable with their roles and to standardize their procedures.

Manipulation Checks

A manipulation check is an attempt to directly measure whether the independent variable manipulation has the intended effect on the participants. Manipulation checks provide evidence for the construct validity of the manipulation (construct validity was discussed in Chapter 4). If you are manipulating anxiety, for example, a manipulation check will tell you whether participants in the high-anxiety group really were more anxious than those in the low-anxiety condition. The manipulation check might involve a self-report of anxiety, a behavioral measure (such as number of arm and hand movements), or a physiological measure. All manipulation checks, then, ask whether the independent variable manipulation was in fact a successful operationalization of the conceptual variable being studied. Consider, for example, a manipulation of physical attractiveness as an independent variable. In an experiment, participants respond to someone who is supposed to be perceived as attractive or unattractive. The manipulation check in this case would determine whether participants do rate the highly attractive person as more physically attractive.

Manipulation checks are particularly useful in the pilot study to decide whether the independent variable manipulation is in fact having the intended effect. If the independent variable is not effective, the procedures can be changed. However, it is also important to conduct a manipulation check in the actual experiment. Because a manipulation check in the actual experiment might distract participants or inform them about the purpose of the experiment, it is usually wise to position the administration of the manipulation check measure near the end of the experiment; in most cases, this would be after measuring the dependent variables and prior to the debriefing session.

A manipulation check has two advantages. First, if the check shows that your manipulation was not effective, you have saved the expense of running the actual experiment. You can turn your attention to changing the manipulation to make it more effective. For instance, if the manipulation check shows that neither the low- nor the high-anxiety group was very anxious, you could change your procedures to increase the anxiety in the high-anxiety condition.

Second, a manipulation check is advantageous if you get nonsignificant results—that is, if the results indicate that no relationship exists between the independent and dependent variables. A manipulation check can identify whether the nonsignificant results are due to a problem in manipulating the independent variable. If your manipulation is not successful, it is only reasonable that you will obtain nonsignificant results. If both groups are equally anxious after you manipulate anxiety, anxiety cannot have any effect on the dependent measure. Page 196What if the check shows that the manipulation was successful, but you still get nonsignificant results? Then you know at least that the results were not due to a problem with the manipulation; the reason for not finding a relationship lies elsewhere. Perhaps you had a poor dependent measure, or perhaps there really is no relationship between the variables.

Debriefing

The importance of debriefing was discussed in Chapter 3 in the context of ethical considerations. After all the data are collected, a debriefing session is usually held. This is an opportunity for the researcher to interact with the participants to discuss the ethical and educational implications of the study.

The debriefing session can also provide an opportunity to learn more about what participants were thinking during the experiment. Researchers can ask participants what they believed to be the purpose of the experiment, how they interpreted the independent variable manipulation, and what they were thinking when they responded to the dependent measures. Such information can prove useful in interpreting the results and planning future studies.

Finally, researchers may ask the participants to refrain from discussing the study with others. Such requests are typically made when more people will be participating and they may talk with one another in classes or residence halls. People who have already participated are aware of the general purposes and procedures; it is important that these individuals not provide expectancies about the study to potential future participants.

ANALYZING AND INTERPRETING RESULTS

After the data have been collected, the next step is to analyze them. Statistical analyses of the data are carried out to allow the researcher to examine and interpret the pattern of results obtained in the study. The statistical analysis helps the researcher decide whether there really is a relationship between the independent and dependent variables; the logic underlying the use of statistical tests is discussed in Chapter 13. It is not the purpose of this book to teach statistical methods; however, the calculations involved in several statistical tests are provided in Appendix C.

COMMUNICATING RESEARCH TO OTHERS

The final step is to write a report that details why you conducted the research, how you obtained the participants, what procedures you used, and what you found. A description of how to write such reports is included in Appendix A. After you have written the report, what do you do with it? How do you communicate the findings to others? Research findings are most often submitted as journal articles or as papers to be read at scientific meetings. In either case, Page 197the submitted paper is evaluated by two or more knowledgeable reviewers who decide whether the paper is acceptable for publication or presentation at the meeting. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Professional Meetings

Meetings sponsored by professional associations are important opportunities for researchers to present their findings to other researchers and the public. National and regional professional associations such as the American Psychological Association (APA) and the Association for Psychological Science (APS) hold annual meetings at which psychologists and students present their own research and learn about the latest research being done by their colleagues. Sometimes, verbal presentations are delivered to an audience. However, poster sessions are more common; here, researchers display posters that summarize the research and are available to discuss the research with others.

Journal Articles

As we noted in Chapter 2, many journals publish research papers. Nevertheless, the number of journals is small compared to the number of reports written; thus, it is not easy to publish research. When a researcher submits a paper to a journal, two or more reviewers read the paper and recommend acceptance (often with the stipulation that revisions be made) or rejection. This process is called peer review and it is very important in making sure that research has careful external review before it is published. As many as 90% of papers submitted to the more prestigious journals are rejected. Many rejected papers are submitted to other journals and eventually accepted for publication, but much research is never published. This is not necessarily bad; it simply means that selection processes separate high-quality research from that of lesser quality. SELECTING RESEARCH PARTICIPANTS ASSIGNMENT.

Many of the decisions that must be made when planning an experiment were described in this chapter. The discussion focused on experiments that use the simplest experimental design with a single independent variable. In the next chapter, more complex experimental designs are described.

ILLUSTRATIVE ARTICLE: CONDUCTING EXPERIMENTS

Many people behave superstitiously. That is, they may believe that their lucky shirt helps them with an exam, or that washing a uniform after a game removes the “luck,” or that winning the lottery is dependent on playing one’s lucky numbers. Many of us believe that, indeed, these superstitions do not really affect outcomes. Superstition has been studied in psychology for some time. B. F. Skinner (1947) demonstrated that superstitious Page 198behavior could be seen in a pigeon! More recently, Damisch, Stoberock, and Mussweiler (2010) decided to see if they could observe any effect that superstitious behaviors had on several different performance measures, including putting in golf, motor dexterity, memory, and performance on a word jumble puzzle.

Over four different experiments, the researchers varied participants’ perceptions of “luck” and then measured performance. In the first experiment, university students were randomly assigned to conditions wherein they were asked to putt using either a “lucky ball” (condition 1) or a “neutral ball” (condition 2). Participants in the “lucky ball” condition were statistically better putters than those in the “neutral ball” condition.

First, acquire and read the article:

Damisch, L., Stoberock, B., & Mussweiler, T. (2010). Keep your fingers crossed! How superstition improves performance. Psychological Science, 21, 1014–1020. doi:10.1177/0956797610372631

Then, after reading the article, consider the following:

1. For each of the four experiments, describe how the manipulation of the independent variable was straightforward or staged.

2. In this chapter, we discuss three types of dependent measures: self-report, behavioral, and physiological. In the experiments presented in this paper, what types of dependent measures were used? Could other types of dependent measures have been used? How so?

3. Was the dependent measure used in Experiment 1 sensitive? How so?

4. Did these researchers use any manipulation checks in their experiments? Design a manipulation check for Experiment 2.

5. This paper includes four experiments. Given that these researchers were interested in superstition, why was using multiple studies a good thing for the internal validity of the study?

6. How good was the internal validity of this series of studies?

7. How would you extend the study?

Study Terms

Behavioral measure (p. 187)

Ceiling effect (p. 189)

Confederate (p. 183)

Demand characteristics (p. 190)

Double-blind experiment (p. 193)

Electroencephalogram (p. 187)

Electromyogram (p. 187)

Expectancy effects (experimenter bias) (p. 192)

Filler items (p. 190)

Page 199Floor effect (p. 189)

Functional MRI (p. 188)

Galvanic skin response (p. 187)

Manipulation check (p. 195)

Manipulation strength (p. 185)

MRI (p. 188)

Physiological measure (p. 187)

Pilot study (p. 194)

Placebo group (p. 191)

Self-report (p. 186)

Sensitivity (p. 189)

Single-blind experiment (p. 193)

Staged manipulation (p. 183)

Straightforward manipulation (p. 181)

Review Questions

1. What is the difference between staged and straightforward manipulations of an independent variable?

2. What are the general types of dependent variables?

3. What is meant by the sensitivity of a dependent measure? What are ceiling and floor effects?

4. What are demand characteristics? Describe ways to minimize demand characteristics.

5. What is the reason for a placebo group?

6. What are experimenter expectancy effects? What are some solutions to the experimenter bias problem?

7. What is a pilot study?

8. What is a manipulation check? How does it help the researcher interpret the results of an experiment?

9. Describe the value of a debriefing following the study.

10. What does a researcher do with the findings after completing a research project?

Activities

1. Dr. Turk studied the relationship between age and reading comprehension, specifically predicting that older people will show lower comprehension than younger ones. Turk was particularly interested in comprehension of material that is available in the general press. Groups of participants who were 20, 30, 40, and 50 years of age read a chapter from a book by theoretical physicist Stephen W. Hawking (1988) entitled A Brief History of Time: From the Big Bang to Black Holes. After reading the chapter, participants were given a comprehension measure. The results showed that there was no relationship between age and comprehension scores; all age groups had equally low comprehension scores. Page 200Why do you think no relationship was found? Identify at least two possible reasons.

2. Recall the experiment on facilitated communication by children with autism that was described on p. 27 in Chapter 2 (Montee, Miltenberger, & Wittrock, 1995). Interpret the findings of that study in terms of experimenter expectancy effects.

3. Your lab group has been assigned the task of designing an experiment to investigate the effect of time spent studying on a recall task. Thus far, your group has come up with the following plan: “Participants will be randomly assigned to two groups. Individuals in one group will study a list of 5 words for 5 minutes, and those in the other group will study the same list for 7 minutes. Immediately after studying, the participants will a list of 10 words and circle those that appeared on the original study list.” Improve this experiment, giving specific reasons for any changes.

4. If you were investigating variables that affect helping behavior, would you be more likely to use a straightforward or staged manipulation? Why?

5. Design an experiment using a staged manipulation to test the hypothesis that when people are in a good mood, they are more likely to contribute to a charitable cause. Include a manipulation check in your design.

6. In a pilot study, Professor Mori conducted a manipulation check and found no significant difference between the experimental conditions. Should she continue with the experiment? What should she do next? Explain your recommendations for Professor Mori.

7. Write a debriefing statement that you would read to participants in the Asch line judgment study (p. 184).

8. Test yourself: Read each statement and then circle the appropriate letter: T (true) or F (false).

a. Most manipulations are straightforward. T F

b. Staged manipulations are designed to get participants involved in the situation and to make them think that it is a real experience. T F

c. A staged experiment may be difficult to replicate by other researchers. T F

d. Straightforward manipulations are often difficult to interpret. T F