Extremity in horizontal and vertical Likert scale format responses. Some evidence on how visual distance between response categories influences extreme responding

In four survey experiments we show that people generally answer more extremely to survey items presented in vertical versus horizontal Likert formats. Our findings suggest that this effect may be at least partly driven by differences in the visual range spanned by the response scale (i.e. the visual distance between endpoint response categories is larger in horizontal than in a vertical format). In addition, compared to traditional horizontal Likert data, vertical Likert data contain more variance, which is mainly non-substantive. As a result, data obtained with scale formats that have different distances between response categories (as is typically the case for vertical vs. horizontal formats) may lead to differences in measurement model parameter estimates like residual terms, and in some cases factor loadings and construct correlations. Based on these results, we provide recommendations on the use of response scale formats in online surveys, bearing in mind that several online survey tool providers promote the use of vertical Likert formats and even automatically change traditional horizontal formats of Likert-type items to vertical Likert formats when viewed on small screens (e.g., on mobile phones).