Background Psychologists are often asked to prepare reports on suspects, complainants and witnesses with intellectual disabilities for court. Increasingly, the Gudjonsson Suggestibility Scales are being used as part of the assessment process. This paper critically examines the use of the Gudjonsson Suggestibility Scales with adults with intellectual disabilities and considers alternative explanations for test data.
Argument It is argued that the scales have been developed in a way that significantly disadvantages people with intellectual disabilities compared with those of average ability. The scales are more likely to elicit acquiescent responses from people with intellectual disabilities as participants are questioned on information they can barely recall. Drawing on models of memory developed in the field of cognitive neuroscience, it is argued that this is a consequence of examining unimodal input into semantic memory, which is impaired in people with intellectual disabilities. Police interviews are rarely concerned with semantic memory alone but with autobiographical event memory of multimodal input. Research on people with intellectual disabilities' event memory shows higher levels of accuracy, less of a tendency to acquiesce and greater resistance to suggestion.
Conclusions Currently, the Gudjonsson Suggestibility Scales are the only tests available for the assessment of interrogative suggestibility. However, psychologists using these scales with adults with intellectual disabilities should do so with caution as their validity is questionable. Studies of intellectually disabled adults' autobiographical event memory show that they can provide reasonably accurate accounts of events and resist questions designed to alter their account.