Mr. Seemy’s class was discussing the implications that different cultural images have for the way people see themselves. Jacky chimed in, “I read about a study where they found that the type of doll young girls are exposed to plays a role in how the girls see their own bodies.”

“Yes, I know which study you’re talking about,” said Mr. Seemy. “Experimenters read stories to a group of five- to eight-year-old girls, and had the girls follow along with books that had different sets of illustrations. One set of illustrations used the well-known, super-thin Barbie doll. Another set of illustrations featured the Emme doll, which looks more like a real woman. A third set of illustrations didn’t show any dolls, just images of objects and scenery relating to the story. After undergoing this process, girls in kindergarten and first grade who looked at the Barbie illustrations were less satisfied with their own bodies’ appearance than girls who looked at the Emme illustrations or the illustrations without any dolls.”

“That’s interesting,” said Aliyah. “I think it’s important to empower kids at an early age to resist unrealistic expectations of how they ought to look. Some girls feel so bad about their bodies that they end up denying themselves enough food.”

“How do they know the doll was the reason that some girls felt worse about their bodies after the experiment?” asked Manvi. “What if the stories were different?”

“Great question,” said Mr. Seemy. “The stories were exactly the same—a ‘controlled variable.’ A variable is anything that can change or differ in an experiment. Researchers distinguish between three basic kinds of variables: independent variables, dependent variables, and controlled variables.

“An independent variable,” continued Mr. Seemy, “is a variable that is changed by the scientists in an experiment. A dependent variable is something scientists observe that is caused by, or depends on, the influence of the independent variable. And a controlled variable remains constant in any experiment, regardless of changes to the independent variable.”

Mr. Seemy drew the first table below and helped his students check off which variables were independent, dependent, and controlled. Then, he drew a second table for another experiment, and challenged his students to identify the variables correctly.

Discussion Question:

Discuss the different variables in the doll experiment. Then, discuss why you identified each of the variables in the fertilizer experiment the way you did.