Body dysmorphic disorder (BDD) is a mental illness in which people focus critically and negatively on the fine details of their bodies. The disorder is linked to eating disorders and to behaviors such as repeated checking in the mirror or embarassment about one's body.

Science News Daily reports a study that used fMRI techniques to study brain activity in visual processing regions for 14 people with BDD and 14 healthy controls. They showed all the participants a series of photos of houses that were highly detailed, normal, or less detailed.

According to the news story,

The researchers found that the BDD patients had abnormal brain activation patterns when viewing pictures of the less-detailed houses: The regions of their brains that process these visual elements showed less activation than the healthy controls.

This study is an example of a factorial design.

a) What are the independent variables in this study? How many levels are there for each IV?

b) What is the dependent variable in this study?

c) Sketch a graph of the results of the study, according to the description quoted above. You may not know the exact results for each cell, but you can estimate what the pattern looks like.

d) According to the results described (and the graph you drew), do you detect an interaction in these results? How about main effects?