Exploring the vividness of mental imagery and eidetic imagery in people with intellectual disability (ID) in comparison with typically developing (TD) individuals

Background: Mental imagery (MI) has been described as the "ability to simulate in the mind information that is not currently being perceived by the sense organs" (Moran, 2012, p. 166). The vividness of mental imagery has been defined as the clarity, brightness, or intensity of an image as reported by the individual (Marks, 1973). There are many studies conducted on vividness in typically developing (TD) individuals, however, no attempt has been made either to assess the vividness of mental imagery in people with intellectual disability (ID) or compare it with that of typically developing (TD) adults.

Metods: A vividness of imagery test (comprising a modified version of the Vividness of Visual Imagery Questionnaire 2, (VVIQ-2; Marks, 1995), and two items of the Age Projection Test, (APT; Ahsen, 1988) were administered to participants with mild, moderate, and severe ID. Their performance on the vividness scale was compared with typically developing individuals. Measures for cognitive and adaptive functioning were administered to ascertain the ID level of participants.

Results: The results of this study reveal a non-significant group difference between people with mild ID, moderate ID, and TD on the vividness of mental imagery and eidetic imagery. People with severe ID performed significantly lower than the other three groups.

Conclusion: Despite their cognitive impairment, a non-significant difference between the performance of people with mild and moderate ID and typically developing individuals on imagery vividness scale is noteworthy.