A new two-dimensional question format in web survey design: assimilation and contrast effects

Computer- and web-based survey technology has enabled the use of question formats and layouts that would be difficult
or even impossible to implement with traditional paper questionnaires. The present article investigates context effects—
specifically assimilation versus contrast effects—in connection with four web survey question designs. Three traditional
types of matrix questions are experimentally tested against a new two-dimensional question format referred to as ZEF. This
new question format allows survey practitioners to present two questions at the same time, the responses to which are
entered on the x- and y-axes of a two-dimensional chart. The chart also displays a respondent’s answers to the preceding
two-dimensional questions. This approach accentuates the simultaneous application of two dimensions of a question and
encourages the comparison of pairwise items across the dimensions. The two-dimensional format generates a higher number
of assimilation effects as compared with the three traditional matrix question formats. This suggests that instead of conceptual
interconnection of items, context effect formation in ZEF is dominated by the visual proximity of the item scales and the
common region of the two-dimensional chart.