Discriminant validity where there should be none: Positioning same-scale items in separated blocks of a questionnaire

In questionnaires, items can be presented in a grouped format (same-scale items are presented in the same block) or in a randomized format (items from one scale are mixed with items from other scales). Some researchers have advocated the grouped format because it enhances discriminant validity. The current study demonstrates that positioning items in separate blocks of a questionnaire may indeed lead to increased discriminant validity, but this can happen even in instances where discriminant validity should not be present. In particular, the authors show that splitting an established unidimensional scale into two arbitrary blocks of items separated by unrelated buffer items results in the emergence of two clearly identifiable but artificial factors that show discriminant validity.