Suggestibility and salience in people with intellectual disabilities: An experimental critique of the Gudjonsson Suggestibility Scale

Abstract

Aim: The Gudjonsson Suggestibility Scale (GSS) assesses suggestibility by asking respondents to recall a short story, using leading questions and pressure to change their responses. Suggestibility, as assessed by the GSS, is elevated in people with intellectual disabilities. Unlike real life incidents, the information presented is of no personal significance to the respondent. The aim of the present study was to investigate whether this factor influences suggestibility in people with intellectual disabilities. Method: We created two alternative suggestibility scales (ASS and ASS2), based on real events in a learning disabilities day service. In Experiment 1, two groups of service users (n = 20) were administered both the GSS and the ASS, presented in a counterbalanced order. The experimental group had witnessed the events described in the ASS, which took place 18 months earlier. The control group attended a different day service; therefore, for this group, the information presented in the GSS and the ASS tasks was equally unfamiliar. In Experiment 2, both groups of participants were administered the ASS2, which described events that took place one month earlier. Results: In the control group, the GSS, ASS, and ASS2 did not differ either in recall of the information presented, or in suggestibility. In the experimental group suggestibility was decreased by a third for the ASS, relative to the GSS, and by two thirds for the ASS2. Therefore, suggestibility is decreased by familiarity and the decrease is greater for more recent events. Recall was higher for the ASS than for the GSS, but there was no difference in recall between the ASS and ASS2. Therefore, decreases in suggestibility for familiar material cannot be explained simply in terms of increased recall. Implications: We believe that this study is the first to report that suggestibility for events that have been witnessed is less than for arbitrary events. A crime that has been witnessed is likely to be better recalled than an impersonal story. The results suggest that the GSS is likely to over-estimate how suggestible a person is likely to be when the event in question is personally significant. This may lead to people with learning disabilities being prevented from testifying in court because it is mistakenly inferred from the GSS that their testimony would be unreliable.