The Gudjonsson test, more formally called the Gudjonsson Suggestibility Scale (GSS), is a structured psychological measure of interrogative suggestibility. This refers to how likely a person is to accept misleading information during questioning and to change an answer after experiencing pressure or negative feedback from the interviewer.¹
The test was developed by Icelandic-British psychologist Gísli H. Gudjonsson for use in research and forensic psychological assessment. It is especially associated with questions about police interviews, eyewitness testimony, confessions, and a person’s vulnerability to suggestion.²
What does the Gudjonsson test measure?
The GSS measures two related responses:
Yield: accepting misleading or leading information.
Shift: changing an answer after the interviewer says that a previous answer was incorrect and asks the person to answer again.
These scores are combined to produce an overall Total Suggestibility score. The test is intended to measure responses to questioning under standardized conditions, not suggestibility in every area of a person’s life.¹
How is the test administered?
The participant hears a short story and is then asked a series of questions about it. Some questions contain misleading details—for example, information that was not included in the original story or that contradicts it.
The procedure generally involves:
Listening to a brief story.
Answering a series of questions about the story.
Receiving negative feedback, such as being told that several answers were incorrect.
Answering the critical questions again.
The examiner records whether the participant accepts misleading information and whether the participant changes answers after the negative feedback.²
The procedure is standardized, so administration and scoring should be conducted by someone with appropriate training and access to the relevant professional materials.
What are GSS1 and GSS2?
GSS1 and GSS2 are parallel forms of the Gudjonsson Suggestibility Scale. They use different stories and question sets while following the same general procedure. GSS2 was developed to provide a second form and to reduce the effects of repeated exposure to the same material.³
Both forms are designed to produce measures of:
Yield 1
Yield 2
Shift
Total Suggestibility
In the standard scoring approach, Total Suggestibility is generally calculated from Yield 1 and Shift. Yield 2 is used in evaluating the participant’s responses after feedback and helps show how answers changed, but it is not ordinarily added as a separate component of the total score.²
What is the difference between yield and shift?
Yield concerns the person’s response to misleading questions. A participant may accept a suggested detail even though it was not present in the story.
Shift concerns what happens after the examiner applies negative feedback. A person may change an answer because they have become uncertain, because they believe the examiner knows the correct answer, or because they want to comply with the examiner.
These processes may involve different psychological factors. Yield has been associated more closely with memory and cognitive variables, while Shift appears to be influenced more strongly by interpersonal pressure, emotional factors, and compliance.⁴
Is the Gudjonsson test a test of lying?
No. The GSS is not a lie detector.
It does not determine whether a person is telling the truth about a real event. Instead, it measures how the person responds to misleading questions and negative feedback in a controlled task.
A high score may indicate increased vulnerability to suggestion under the conditions of the test. It does not prove that a person has lied, that a confession is false, or that testimony is unreliable.
Does a high score mean that someone is easily manipulated?
Not necessarily. A high GSS score indicates that the person accepted misleading information, changed answers after feedback, or both during the assessment. That result may reflect several influences, including:
Memory limitations
Intellectual or cognitive difficulties
Anxiety
Low confidence
Desire to please the examiner
Compliance with perceived authority
Difficulty resisting social pressure
Problems understanding the questions
The result should therefore be interpreted as evidence of vulnerability under particular questioning conditions—not as a complete description of the person’s character or abilities.²
Does the test distinguish suggestibility from compliance?
Only imperfectly. This is one of the principal limitations of the GSS.
A person may accept a suggested answer because the misleading information has influenced their memory or belief. Alternatively, they may give the suggested answer simply to satisfy the interviewer, avoid conflict, or comply with perceived authority.
Both processes can produce the same observable response. Researchers have therefore questioned how clearly the GSS separates suggestibility, meaning acceptance or internalization of suggested information, from compliance, meaning outward agreement without necessarily changing one’s private belief.⁵
This limitation is especially relevant when interpreting Shift scores.
Is the Gudjonsson test reliable?
The reliability evidence is mixed.
Early research reported favorable internal-consistency findings for parts of the scale, and later studies have found evidence that the GSS can produce meaningful and repeatable results in some groups.⁶ However, other studies have found only modest test–retest stability or low internal consistency for particular scores, especially in some samples and language versions.⁵
This means that a score should not be treated as perfectly precise or permanently stable. A person’s performance may be affected by factors such as fatigue, anxiety, familiarity with testing, language comprehension, motivation, and the relationship with the examiner.
The most responsible interpretation considers the pattern of results and the broader assessment rather than relying on one number.
Is the Gudjonsson test valid?
Research provides some support for the test’s validity, but its interpretation requires care.
Studies have reported relationships between GSS performance and cognitive, emotional, and personality-related variables. Research involving forensic groups has also found patterns broadly consistent with the idea that some people are more vulnerable than others to misleading questions and interpersonal pressure.⁴
Cross-cultural studies have produced broadly comparable findings, although scores can be affected by translation, language, education, cultural expectations, and the characteristics of the sample being tested.⁷
The GSS therefore appears to measure a meaningful aspect of interrogative behavior, but it should not be treated as a complete or universally precise measure of suggestibility.
Can the test predict false confessions?
The GSS may provide information about a person’s vulnerability to certain pressures, but it cannot predict a false confession on its own.
False confessions can arise through multiple pathways, including:
Threats or promises
Lengthy questioning
Sleep deprivation or exhaustion
Fear of consequences
Desire to protect another person
Confusion or misunderstanding
Mental-health difficulties
Developmental immaturity
Belief that confessing will bring an immediate benefit
Internalization of information supplied by investigators
A GSS score may be relevant to a broader forensic evaluation, but it cannot establish that a particular confession was false or involuntary. The actual interview must also be examined, including its duration, language, pressure, promises, threats, repetition, and the evidence presented to the suspect.⁸
Is the test used with children and adolescents?
The principles measured by the GSS may be relevant when assessing children and adolescents, but age, language ability, intellectual development, memory, and understanding of authority must be considered carefully.
Children and adolescents are not simply smaller versions of adults. Their responses to questioning can be affected by developmental differences in memory, suggestibility, social understanding, and the ability to resist pressure.
A properly qualified professional should select and interpret any assessment tool with the person’s developmental level and the legal question in mind.
Can someone take the test online?
An online quiz cannot be treated as a valid administration of the Gudjonsson Suggestibility Scale.
The GSS is a controlled psychological instrument. Its administration, instructions, materials, timing, scoring, and interpretation all matter. An informal online exercise may illustrate the general idea of suggestibility, but it cannot provide a forensic score or replace an assessment by a qualified professional.
Who should administer and interpret it?
The GSS should be administered and interpreted by a suitably trained professional who understands psychological assessment and the forensic context in which the results may be used.
Interpretation should include:
The person’s age and developmental history
Language and educational background
Intellectual and memory functioning
Emotional state
Mental-health history
The exact testing conditions
The interview or interrogation being evaluated
Other available evidence
The GSS should normally be one part of a broader assessment rather than the sole basis for an opinion.²
What are the main strengths of the test?
The GSS has several strengths:
It uses a standardized procedure.
It separates responses to misleading questions from responses to later pressure.
It provides a structured way to discuss interrogative vulnerability.
It has been studied in forensic and nonforensic groups.
It has encouraged research on suggestibility, compliance, memory, and confessions.
Its greatest value is that it gives professionals a common framework for examining how a person responds to misleading questions and interviewer feedback.
What are its main limitations?
The principal limitations are:
Reliability varies across samples and scores.
Test performance may be affected by language, culture, anxiety, and cognitive ability.
The test does not perfectly separate suggestibility from compliance.
A laboratory-style task is not identical to a real police interrogation.
A high score does not prove that a person is unreliable in all settings.
The test cannot determine whether a particular statement is true or false.
It should not be used as a stand-alone basis for legal conclusions.
Bottom line
The Gudjonsson Suggestibility Scale is a structured measure of how a person responds to misleading questions and interpersonal pressure. It can contribute useful information to research and forensic assessment, especially when interpreted alongside cognitive, developmental, emotional, and interview evidence.
It is not a lie detector, a general personality test, or a stand-alone method for deciding whether a confession or testimony is true. The most careful interpretation treats the GSS as one source of information about possible vulnerability under particular questioning conditions.
Notes
Gísli H. Gudjonsson, “A New Scale of Interrogative Suggestibility,” Personality and Individual Differences 5, no. 3 (1984): 303–314.
Gísli H. Gudjonsson, The Psychology of Interrogations, Confessions and Testimony (Chichester, UK: Wiley, 1992).
Gísli H. Gudjonsson, The Psychology of Interrogations and Confessions: A Handbook (Chichester, UK: Wiley, 2003).
Gísli H. Gudjonsson, “Interrogative Suggestibility: Historical and Theoretical Aspects,” in The Handbook of Eyewitness Psychology: Memory for Events, edited by Michael P. Toglia, J. Don Read, David F. Ross, and R. C. L. Lindsay (Mahwah, NJ: Lawrence Erlbaum Associates, 2007).
Harald Merckelbach, Peter Muris, Ineke Wessel, and Peter J. van Koppen, “The Gudjonsson Suggestibility Scale (GSS): Further Data on Its Reliability, Validity, and Metamemory Correlates,” Social Behavior and Personality: An International Journal 26, no. 3 (1998): 203–210.
Gísli H. Gudjonsson and John Clare, “The Development of the Gudjonsson Suggestibility Scale,” in The Psychology of Interrogations, Confessions and Testimony, by Gísli H. Gudjonsson (Chichester, UK: Wiley, 1992).
Carla M. P. N. Baptista, Rui A. B. F. R. Gonçalves, and Gísli H. Gudjonsson, “The Gudjonsson Suggestibility Scale: A Study of Its Validity in a Portuguese Sample,” Psychology, Crime & Law 19, no. 9 (2013): 787–798.
Gísli H. Gudjonsson, The Psychology of False Confessions: Forty Years of Science and Practice (Chichester, UK: Wiley, 2018).