Measuring social desirability amongst men with intellectual disabilities: The psychometric properties of the Self- and Other-Deception Questionnaire-Intellectual Disabilities

Background: Social desirability has been construed as either inaccurately attributing positive characteristics to oneself (self-deception), or inaccurately denying that one possesses undesirable characteristics to others (other-deception or impression management). These conceptualisations of social desirability have not been considered in relation to people with intellectual disabilities (IDs), but they are important constructs to consider when undertaking a psychological assessment of an individual, especially within forensic contexts. Therefore, we revised two existing measures of self- and other-deception and considered their psychometric properties. 

Methods: Thirty-two men with mild IDs and 28 men without IDs completed the Self- and Other-Deception Questionnaires-Intellectual Disabilities (SDQ-ID and ODQ-ID) on two occasions, two weeks apart. 

Results: Men with IDs scored significantly higher on the SDQ-ID and the ODQ-ID than men without IDs. However, these differences disappeared when Full Scale IQ, Verbal IQ and Performance IQ were controlled in relation to the SDQ-ID, and partially disappeared in relation to the ODQ-ID. The SDQ-ID and the ODQ-ID had substantial internal consistency in relation to men with IDs (k=0.82 and 0.84 respectively). The test-retest reliability of the SDQ-ID was good (r_i=0.68), while the test-retest reliability of the ODQ-ID was moderate (r_i=0.56), for men with IDs. The SDQ-ID had moderate (k=0.60) and the ODQ-ID had substantial (k=0.70) internal consistency in relation to men without IDs, while the test-retest reliability of the SDQ-ID was excellent (r_i=0.87) as was the case for the ODQ-ID (r_i=0.85). 

Conclusions: The SDQ-ID and the ODQ-ID have satisfactory psychometric properties in relation to men with and without IDs. Future research using these instruments is proposed.