Many of us are somewhat familiar with the physiological lie detector--a machine that records physical signs of anxiety (such as sweating or blood pressure) while people answer questions. More recently, research from psychologist Dr. James Pennebaker has demonstrated that psychologists can use natural language to distinguish liars from truth-tellers.
The research is discussed in this Huffington Post article. The article explains that the researchers analyzed a set of stories (from court transcripts or journalism) that were known to be either truthful or false. They submitted the text of the stories to a computerized system known as LIWC (Linguistic Inquiry and Word Count). The program can tally different types of speech (such as pronouns, verbs, positive or negative emotion words) in any type of text. There were four differences between the language used in true and false stories:
An analysis of the words used in these stories revealed a few reliable differences. Stories that were true had more words in them and more details than those that were fake.
The true stories had fewer emotion terms in them than the fakes.
The true stories had fewer verbs than the fakes.
Finally, the true stories had more first-person pronouns in them than the fakes.
For example, this last example was supported by court transcripts, where they found:
defendants who were found guilty at trial but were later exonerated based on DNA evidence often used first-person pronouns. The expressed their innocence by talking about themselves. Defendants who were guilty of perjury used third-person pronouns (like he and she) as they tried to shift blame to other people.
a) What are the variables in this pattern of results? What kind of study is this--correlational or experimental?
a) The variables here are the different qualities of speech (such as number of words, number of verbs, or number of first-person pronouns), and the known truthfulness of the text. Both of these variables are measured--they occurred more or less naturally. Therefore, this is a correlational study.
b) You could view qualities of speech (for example, the number of first-person pronouns) as an operational definition of "lying." That is, the LIWC system can be seen as a lie detector. To decide if this measure of lie detection is a valid one, the researchers used the known groups paradigm of recruiting examples of known liars and known truthtellers. The fact that the liars and truthtellers showed the predicted differences in language use provides evidence supporting that the language use measure may be a valid measure of lying. In this sense it is similar to the strategy that Beck and colleagues used when they confirmed that scores on the Beck Depression Inventory were higher for known groups of depressed people than for non-depressed people (as described in Chapter 5).