General Recognition Theory (GRT)
Perceptual input from the environment is often complex and multidimensional. Let's take the example of faces. The combination of attributes and features that make up a face is already multidimensional, including such qualities as color, size and shape of components such as noses, eyes, mouth, cheeks, etc. But on top of that, our goals in looking at faces vary and can include identifying many factors, such as the age, gender, familiarity, emotion, etc. How do all of these factors interact? For example, when trying to determine the gender of a face, does the particular emotion bias our gender decision, or are gender and emotion perception independent? Such questions can be empirically tested using GRT analyses.