In forensic psychology, dissimulation refers to a person's deliberate attempt to misrepresent their psychological symptoms— either by exaggerating (commonly called "faking bad")  or minimizing ("faking good").  This often happens in legal situations.

For example, someone may fake bad to avoid punishment or get financial compensation, or fake good to win child custody.

To catch such misleading responses, psychologists use personality tests like the MMPI (Minnesota Multiphasic Personality Inventory). This test has special validity scales that help check if the answers are truthful. The most common ones are:

  • F Scale
  • L Scale
  • Inconsistency Scale

 

F Scale (Infrequency Scale / Detecting “Fake Bad”):

The F Scale is designed to catch people who are faking bad, meaning they are exaggerating their symptoms to look more mentally ill than they actually are. This scale includes items that most people, even those with real mental disorders, rarely agree with.

Purpose: Its main role is to detect malingering (faking or exaggerating illness).

Forensic relevance: It is very important in criminal cases.  For example, a defendant might try to appear mentally incompetent so they cannot be put on trial, or claim serious illness to avoid legal punishment.

Example items: “I hear voices that others do not.” “Sometimes I feel that my thoughts are being controlled by another force.” If a person answers “True” to many of these unusual statements, it raises suspicion that they are pretending to be more disturbed than they really are.


L Scale (Lie Scale / Detecting “Fake Good”):

The L Scale is designed to catch people who are faking good, meaning they are trying to hide flaws and appear morally perfect. This scale contains questions about very small weaknesses or everyday flaws that almost everyone has.

Purpose: Its main role is to find people who want to look unrealistically positive or “too good to be true.”

Forensic relevance: It is especially useful in child custody cases, job screenings, or parole evaluations, where someone may want to look perfect so they get a favorable outcome.

Example items: “I have never told a lie.” “I never feel angry at anyone.” Most honest people will admit to telling a lie or feeling angry sometimes. If someone answers “True” to these items, it suggests dishonesty or a social desirability bias—they are trying too hard to look good.

 

Inconsistency Scale (Detecting Contradictory Responses):

The Inconsistency Scale is designed to check whether a person gives contradictory answers to questions that measure the same idea. When someone answers in a way that does not logically make sense, it can mean they are answering randomly, carelessly, or even trying to deceive.

Purpose: Its main role is to identify contradictory or careless patterns in responses.

Forensic relevance: If the Inconsistency Scale shows many contradictions, it means the person’s test answers are not reliable or valid. In such cases, the results may be rejected in court or other legal decisions because they cannot be trusted.

Example item pairs:

Item A: “I enjoy socializing with large groups.” Item B: “I prefer to avoid social situations.” If someone answers “True” to both, it is a contradiction. This may suggest the person is confused, not paying attention, or deliberately misleading.

Item A: “I feel tired most of the time.” Item B: “I am full of energy.” Since both cannot be true at the same time, choosing “True” for both is flagged by the Inconsistency Scale.