By Manoj Thomas (Cornell) and Ellie J. Kyung (Dartmouth College)
Managers and researchers increasingly use textboxes and slider scales interchangeably to collect price, donations, or willingness-to-pay information from people. For example, Priceline collects Name Your Own Price bid information through a textbox on its website, but through a slider scale through its mobile app. Many times, these format choices are made for interface considerations. However, this research suggests that these response formats should not be used interchangeably because numeric responses elicited on slider scales can be systematically different from those elicited through textboxes.
When people use textboxes to submit numeric responses, they evaluate numeric magnitudes relative to the starting point of the response range. In contrast, when people use slider scales, they evaluate numeric magnitudes by considering the visual distances from the starting point as well as the endpoint of the response range. Because of this, numeric responses on slider scales are more likely to be assimilated towards the endpoint of the scale. This slider scale endpoint assimilation effect is demonstrated through 11 experiments (7 in the paper, 4 in the appendix), showing that it varies for ascending and descending payment formats and that its strength depends on factors related to visualization of the slider scale itself.
For ascending payment formats, where consumers offer payment values higher than a starting price (e.g., eBay), slider scales elicit higher values than textboxes. For descending payment formats, where consumers offer payment values lower than a starting price (e.g., Priceline), slider scales elicit lower values than textboxes. Across the studies, in ascending payment formats where slider scales started at a zero value, values solicited through slider scales were on average 66% higher than those solicited through textbox values. For ascending payment formats where slider scales started at non-zero values (i.e. $239, $259, $279), values solicited through slider scales were on average 5% higher than those solicited through textboxes (taking into account the starting value, the relative difference between these values in terms of distance from starting point is 52%). For descending payment formats, values solicited through textboxes were on average 10% higher than those solicited through slider scales.
Thomas and Kyung believe that consumers bid shift when using slider scales because of our mental perception of numbers. We typically picture a mental number line with values from left to right, but our mental number line tends to be logarithmic rather than linear in nature and the distance between numbers is not consistent. “The psychological impact of increasing a price from $10 to $20 will be greater than that of increasing it from $30 to $40,” Thomas and Kyung write. When using a textbox, we rely on this logarithmic number line in our mind. But when using a slider scale, we rely on a more linearized number line that is stretched towards a visual ending point, resulting in higher bids for ascending payment formats.
This research demonstrates that seemingly simple interface changes can have a material effect on consumer payments because slider scales can change how consumer mentally visualize prices and shift whether they perceive them as low, medium, or high. Furthermore, this work suggests that this effect extends not only to slider scales, but any format that creates a visual line. Thus managers should exercise caution when making format choices involving any kind of numeric payment, bidding, or donation information. Thomas and Kyung write, “If you’re thinking about using a slider scale versus a text box on your interface, remember: response format does matter.