The memory confusion protocol is a technique used by social psychologists

Social psychology

Social psychology is the scientific study of how people's thoughts, feelings, and behaviors are influenced by the actual, imagined, or implied presence of others. By this definition, scientific refers to the empirical method of investigation. The terms thoughts, feelings, and behaviors include all...

 to discover whether subjects are categorizing

Categorization

Categorization is the process in which ideas and objects are recognized, differentiated and understood. Categorization implies that objects are grouped into categories, usually for some specific purpose. Ideally, a category illuminates a relationship between the subjects and objects of knowledge...

 individual

Individual

An individual is a person or any specific object or thing in a collection. Individuality is the state or quality of being an individual; a person separate from other persons and possessing his or her own needs, goals, and desires. Being self expressive...

s into groups and, if so, what characteristics they are using to do so - without the knowledge of the subjects, in order to reduce the risk that subjects will try to conceal their reasons. The technique has three main steps:

1. Subjects are shown photograph
   Photograph
   A photograph is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a CCD or a CMOS chip. Most photographs are created using a camera, which uses a lens to focus the scene's visible wavelengths of light into a reproduction of...
   
   s of the individuals and are asked to form impressions of them.
2. The subjects then see a set of sentences
   Sentence (linguistics)
   In the field of linguistics, a sentence is an expression in natural language, and often defined to indicate a grammatical unit consisting of one or more words that generally bear minimal syntactic relation to the words that precede or follow it...
   
   , each of which is paired with a photograph of the individual who said it.
3. Subjects are not forewarned of the final step, a surprise recall
   Recollection
   Recall in memory refers to the retrieval of events or information from the past. Along with encoding and storage, it is one of the three core processes of memory. There are three main types of recall: free recall, cued recall and serial recall...
   
   task: the sentences are presented in random order, and the subjects must attribute each to the correct individual.

The subjects' mistakes in the recall task reveal how they categorize the individuals: the subjects are more likely to misattribute A's statement to B if they grouped A and B as members of the same category than if they considered them members of different categories.