Personality characteristics attributed to people with intellectual disability

Background: This paper describes a conceptual replication of a study of the personality characteristics that Zigler’s theory of personality attributes to people with intellectual disability. Our study is the first attempt in over twenty years to assess specific personality traits considered in this theory using experimental tasks. Participants and procedure: We studied 25 students of special vocational schools diagnosed with mild intellectual disability, 25 controls from mainstream vocational schools, and 25 primary school students with a similar level of general cognitive ability as that of the students with intellectual disability. We hypothesized that the levels of specific personality traits of people with intellectual disability would differ from those of controls from the general population; we also hypothesized that the direction of differences in regard to these specific personality traits would be the same as assumed in Zigler’s theory. We assessed specific personality traits with seven experimental tasks which we based on descriptions of tasks used by Zigler and his colleagues. Results: We did not observe any statistically significant differences between the scores of participants with intellectual disability and those of the control groups. Conclusions: We explain the results in relation to changes in contextual factors and diagnostic practices over the years. The results indicate the need to conduct replicational studies in the field of clinical psychology.