Abstract
The purpose of this study was to inspect the psychometric properties of a newly developed measure, the General Inventory of Behaviours, Symptoms, and Opinions (GIBSO), and its efficacy in capturing underreporting. Students (N = 169) were randomly allocated to five conditions, (1) honest control (n = 35), and four groups of concealers: (2) psychological symptoms (n = 36), (3) antisocial behaviour (n = 33), (4) somatic complaints (n = 29), and (5) sexual deviance (n = 36). All participants received instructions corresponding to their group allocation and then received symptom inventories of all tested domains, the Supernormality Scale (SS), and GIBSO. Overall, honest participants obtained significantly higher scores on all symptom inventories and exhibited significantly lower underreporting measured by SS and GIBSO than the concealing groups. Further, using GIBSO’s cut-off point of > 20, the classification accuracy was satisfactory, with both sensitivity and specificity at .80 (AUC = .86). Our findings suggest that the GIBSO is a promising measure of symptom and behaviour concealment. However, further investigation involving both general and forensic samples is essential to confirm its efficacy.