Scientific Content Analysis: Lie Detection or Wishful Thinking?

Whether you know it or not, law enforcement agencies all over the world are using a method called Scientific Content Analysis (SCAN) to determine whether or not those they interview are being truthful or deceptive.  According to the Collins Dictionary, SCAN is “the close analysis of the content of statements made to the police by suspects in an attempt to identify innocence or guilt.”

Certainly, we can agree that statements made to police should be closely scrutinized and analyzed, since their truth or falsehood is critical to achieving the ends of justice.  It is alleged that studying the content and structure of a person’s written statements via SCAN will enable a detective or polygraph examiner to accurately judge whether or not the person is being truthful.  Obviously, if that is true, it is a small wonder that law enforcement personnel worldwide are being trained in this process.

The basis for this tool is the idea that certain factors are more likely to be present when a statement is accurate, as opposed to being completely or partially fabricated.  One such factor is that a greater quantity of details are mentioned (e.g., “I saw a yellow and red sunburst pin on the attacker’s left lapel” or “It happened in the rain in the alley next to the Blue Lion convenience store at 8:15 p.m.”) in accurate reports.

As scholarly and scientific as all this sounds, however, SCAN has not shown itself to be effective in revealing deception.  In fact, in an article published in Frontiers in Psychology, the headline conclusion is that “Scientific Content Analysis (SCAN) Cannot Distinguish Between Truthful and Fabricated Accounts of a Negative Event.”  Noting that research on the accuracy of SCAN is scarce, the article states that 117 participants were asked to write down one true and one fabricated statement about a recent negative event in their lives.  Statements were analyzed using 11 criteria derived from SCAN.  The results “indicated that SCAN was not able to correctly classify true and fabricated statements.”  In the researchers’ opinion, “the application of SCAN in its current form should be discouraged.”

Despite these findings (and no support elsewhere) regarding SCAN, it continues to be taught and utilized by law enforcement.  Why should this be?  The simple answer is that we wish it could be as effective as we want it to be.  Unfortunately, like much of what comes out of psychological research, we find that even if SCAN is effective somewhere, it is clearly not effective everywhere.  We want so much to uncover deception–not only in law enforcement, but in critical areas like government and politics–that we childishly cling to methods that sound promising, even in the absence of any credible proof.

To be sure, we as mental health practitioners look for and often find deception in the statements of those we see.  But deception is a deceptively broad term.  It could refer to an outright lie, or it could be a result of wanting to make oneself look better, or it could be to make someone else look worse.  Then there is that long-recognized bugaboo–social desirability.  Especially when it comes to embarrassing details, patients are likely to change the narrative in order that they appear to be the heroes of the story, or at least the innocent victims.

There may well come a time when things like SCAN are clinically verified, and their use justified.  As things stand, however, we are better off trusting the therapist’s instincts over an unproven system of wishful ideas.