In the study about scent influencing painting ratings, what is the independent variable?

The independent variable in the study is the presence or absence of scent in the rooms. This is because the independent variable is the factor that is manipulated by the researchers to observe its effect on another variable, which, in this case, is the viewers' ratings of attractiveness. By changing the scent, or not having it at all, researchers can evaluate how it influences the viewers’ perceptions and ratings of the paintings.

This variable is crucial as it allows for the examination of causal relationships; specifically, how sensory experiences like scent can affect aesthetic judgments. The other factors listed, such as the viewers' ratings, the specific paintings displayed, and the time spent observing the paintings, serve as dependent variables or controlled elements in the study, rather than factors that are manipulated.