The Gudjonsson Suggestibility Scales (GSS 1 and GSS 2) are clinical instruments designed to assess levels of interrogative suggestibility. The scales provide a total score for suggestibility based on responses to leading questions and negative feedback. They also provide measures of memory recall and confabulation. The scales are used in forensic assessments and are also useful research tools, as they provide a quantifiable measure of levels of interrogative suggestibility and an extensive range of norms against which various hypotheses can be tested.
Gisli Gudjonsson developed two scales of interrogative suggestibility designed to be used as forensic tools to help assess the reliability of confessions that have been retracted. The scales also help identify those individuals who may be particularly vulnerable to the pressures associated with police interviews and who, as a result, may require extra care during interviewing. As well as their clinical applications, the scales are also used for research purposes to investigate the social psychological processes that influence the levels of interrogative suggestibility. The GSS 1 and the GSS 2 are identical in structure; each comprises a spoken narrative and 20 questions about that narrative. The content of the GSS 2 narrative is less complex than that of the GSS 1 narrative, and for this reason, the GSS 2 is more commonly used with children or adults with learning disabilities. The scales are therefore parallel in form and produce closely comparable norms.
The narratives each contain 40 distinct pieces of information. Of the 20 questions for both scales, 15 are misleading, suggesting details that are not part of the narrative, and 5 are “true” questions, containing no misleading information. These 5 true questions are interspersed with the misleading or suggestive questions. Administration of the scales initially involves presentation of the narrative to the interviewee; the test administrator, or interviewer, reads out the narrative at a steady pace. Following this, the interviewee is asked to provide immediate free recall of the narrative. There is then a 50-minute delay, followed by the interviewee’s providing delayed recall of the narrative. The 20 questions about the narrative are then asked. When all the questions have been answered, the interviewer gives the interviewee negative feedback. Regardless of level of accuracy, interviewees are told that they have made some mistakes and that it will be necessary to repeat the questions, and they are urged to try and be more accurate. This negative feedback is to be delivered both clearly and firmly so as to convey an appropriate level of interrogative pressure to the interviewee.
Immediate recall and delayed recall are scored according to how many discrete pieces of information are recalled correctly. Information is scored as correct if the meaning is the same as the original item in the narrative. Each correct item earns 1 point, with the maximum score being 40. There is also a score given for Total Confabulation, which comprises a count of the number of distortions and fabrications included when recalling the narrative. A distortion represents a major change to an existing piece of information from the narrative, whereas a fabrication is the introduction of new material. There are four suggestibility scores obtained from the scales: Yield 1 is a measure of all leading questions that are answered affirmatively in the first round of questioning, with the range of possible scores being 0 to 15; Yield 2 is the number of leading questions accepted following the administration of the negative feedback, and again the range of scores is 0 to 15; Shift is a measure of any distinct changes in response to all 20 questions in the second round of questioning, with a range of 0 to 20; and Total Suggestibility is the sum of Yield 1 and Shift, giving a range of 0 to 35.
GSS Reliability and Validity
Factor analysis of the GSS 1 and GSS 2 questions shows two clear factors, with items loading significantly on the appropriate Yield or Shift factors. The scoring of Yield and Shift are nondiscretionary in nature, and studies assessing interscorer reliability confirm that it is very high. Interscorer reliability for immediate and delayed recall is also very high. Scoring of confabulation is slightly less reliable, although correlations show that this is still relatively high. Owing to the nature of the scales, it is not possible to assess test-retest reliability within each scale, as any memory of the narrative and questions affects subsequent testing. However, comparison of the scores of individuals who have completed both the GSS 1 and the GSS 2 has shown high correlations. The scales can therefore be said to have temporal consistency.
There has been extensive research using the scales to test the hypotheses derived from the theoretical model of interrogative suggestibility. The model postulates that interrogative suggestibility is largely dependent on individuals’ cognitive appraisal of the interrogative situation. Research using the scales confirms that suggestible responding is related to cognitive abilities. For example, several studies have demonstrated that GSS scores are negatively related to intelligence and positively correlated with memory capacity. Studies have also shown that increases in the perception of psychological distance between the interviewer and the interviewee are related to increases in scores on the scales. Other research has demonstrated that there are intra-individual differences, such as self-esteem and self-monitoring, that also affect responses on the scales. The research using the scales demonstrates that interrogative suggestibility is a complex response mediated by a range of cognitive and social psychological processes.
- Bain, S. A., Baxter, J. S., & Ballantyne, K. (2007). Self-monitoring style and levels of interrogative suggestibility. Personality & Individual Differences, 42, 623-630.
- Bain, S. A., Baxter, J. S., & Fellowes, (2004). Interacting influences on interrogative suggestibility. Legal and Criminological Psychology, 9, 239-252.
- Gudjonsson, G. H. (2003). The psychology of interrogations and confessions. A handbook. Chichester, UK: Wiley.
- Woolston, R., Bain, S. A., & Baxter, J. S. (2006). Patterns of malingering and compliance in measures of interrogative suggestibility. Personality & Individual Differences, 40, 453-161.
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