In this group work exercise, we will discuss the research of a high school student named David Merrell. Merrell was interested in whether music affects the ability of rats to run a maze. Studies on rats are fairly common in psychology, because the rat brain, while different in many ways from the human brain, has a number of structures that operate similarly to those of humans, including some of the structures involved in learning. Thus, researchers who are interested in how people learn will sometimes begin their study by looking at whether a particular factor is associated with improved learning in rats.

In the study we’ll be talking about in this assignment, David Merrell explored the relationship between music and the speed with which rats finish a maze (speed, in this case, is a measure of how well the rats had learned the maze). The experiment lasted for a month, and during that time, Merrell studied three groups of rats.

The three groups were treated identically EXCEPT for the sound in their living environments:

• The first group of rats (the “Anthrax” group) listed to 10 hours per day of heavy metal music by a band called Anthrax.

• The second group of rats (the “Mozart” group) listened to 10 hours per day of classical music by Mozart.

• The third group of rats (the “Control” group) had no music played at all.

At the very beginning of the study, and once a week until the end of the study, Merrell measured how quickly each rat could run a certain maze. He used the same maze for all the rats and the rats had all had similar training in how to complete the maze, prior to the study. Merrell recorded the average of the three times as each rat’s score for that week of the study. In the questions below, we will be comparing the speed of rats in the different music groups at the start of the study (before any music was played) and in the 4th week of the study.

Please use this background to complete the questions below: 

1. What was the explanatory variable for this study and how do you know?

2. What were the treatment groups and how were they treated differently?

3. What was the response variable for this study and how do you know?

4. Suppose you knew that some rats are naturally faster at the maze, regardless of music. Explain why the use of random assignment would be important in this study—what would it help accomplish or what would it help avoid?