1 Experiments

The experimental method is often preferred in research on behavior because a properly designed experiment can allow cause and effect conclusions to be made. Many studies in social psychology are experiments. These types of studies can be done in a laboratory setting or in a natural setting.

The major components of an experiment are the following. First, one or more variables will be manipulated by the experimenters. Any variable that we manipulate is called an independent variable. A variable (or factor) has at least two different conditions. To be a true experiment, participants must be randomly assigned to the conditions.

Second, there is at least one response or outcome that we are measuring. The response we measure is called the dependent variable.

For example, if we wanted to test whether or not noise makes people behave aggressively, we need at least two levels of noise. One level of the noise variable could be the absence of the noise, or could be a presumably pleasant noise, such as quiet music. Another level would be a loud or annoying noise.

These are the elements of a basic experiment. Use the noise study example to complete the diagram of a basic experiment. Drag the elements of the study to their correct location in the diagram.

This example also introduces an issue that applies to all types of methods. We have to define or operationalize the variables we use in any study. Noise can be defined in many different ways. The researcher needs to show why the particular definition of noise is appropriate. Try the next scenario offering some options for determining how to operationalize noise.

Examples from research

Research by Sheena Iyengar has explored choice and its consequences. In Iyengar and Lepper (2000) several studies tested what happens when there are more or fewer choices available.

Iyengar & Lepper (2000) Study 1

Iyengar and Lepper found a brand of jam (Wilkin and Sons) that had 28 varieties at the time the study was being conducted.  They were also able to get a store to agree to allow them to set up a table in which samples were being offered.

The procedure was as follows:

Shoppers encountered one of two displays. On the table were either 6 (limited-choice condition) or 24 (extensive-choice condition) different jams. On each of two Saturdays, the displays were rotated hourly…(Iyengar & Lepper, 2000, p. 997).

Anyone who came to the sample table was given a coupon for $1 off on a jar of the jam. The coupons were coded to indicate the condition to which the shopper was exposed and the perceived gender of the shopper. Supporting the idea that more choices are not necessarily better, the shoppers who saw the 6-choice table were more likely to buy a jar of jam than were the shoppers who saw the 24-choice table.

Iyengar & Lepper (2000) Study 2

The next study in this article may be of special interest to students, as it compared the impact of choice on whether students completed an extra credit assignment. Students were assigned to an assignment condition by course section in which either 6 or 30 choices of topics for the assignment were given. ^[1] The number of students who turned in the assignment was compared, and a higher percentage of students in the 6-choice condition turned in the paper (74%) than did those in the 30-choice condition (60%).

A note on ethics in this study. All the students received the promised 2 points of extra credit if they turned in the assignment. Although the assignments were also rated for quality,  performance on the assignment was irrelevant for the extra credit — it was only used as one of the dependent variables in the experiment.

Iyengar & Lepper (1999) Study 1

In a TED talk on her choice research, Iyengar described a study with children. (Play the first 20 minutes of the video.)

This study not only provides another example of an experiment with a manipulated (independent) variable, but also it includes a nonmanipulated variable, a method we will discuss in the next chapter.

Iyengar and Lepper (1999) summarized the results as follows:

…the performance and intrinsic motivation of both groups of children were significantly higher in the personal choice condition than in the traditional experimenter choice condition…. the results also indicated that the Asian American children actually performed best and appeared to enjoy the
task most in the mom choice condition (pp. 354-355).