How Interface Design Changes Consumer Behavior

There is no neutral way to present a set of options. Something has to be first, something has to be visually dominant, and something has to happen if the person does nothing. Each of those decisions makes certain choices easier, and easier choices get made more often. Thaler and Sunstein called the person making those decisions a choice architect, and noted that the role cannot be declined — only performed well or badly.

Position and prominence

Order effects in choice sets are well documented and are not explained by search cost alone. Items presented first receive disproportionate attention and disproportionate selection, and the effect persists when all options are simultaneously visible. Visual salience operates similarly: an option rendered with greater contrast, size or whitespace is more likely to be considered and therefore more likely to be chosen.

The commercial reading is that ranking is a recommendation whether or not it is labelled as one. Sorting a list by margin and presenting it as a neutral catalogue is a recommendation the person cannot evaluate, because they have not been told a recommendation was made.

Effort as a lever

Small effort costs suppress behavior disproportionately. This is the operative finding behind one-click purchasing, saved payment details and single-field forms, and it is robust across contexts.

What is less appreciated is that the relationship runs in both directions, and effort can be added deliberately. A confirmation step before an irreversible action, a mandatory pause before a high-value transaction, or a requirement to type a reason before closing an account all reduce the frequency of the behavior. Whether that is protection or obstruction depends entirely on whose interest the friction serves — the distinction examined in friction and effort.

The reference frame the interface constructs

Interfaces establish comparison sets, and comparison sets determine evaluations. Adding an expensive third option changes how the middle option is perceived without changing anything about the middle option. Huber, Payne and Puto (1982) demonstrated the asymmetrically dominated decoy, where an option that is clearly inferior to one alternative but not to another shifts share toward the option that dominates it.

Simonson and Tversky (1992) established the broader principle of context dependence: preferences are constructed relative to the available set, not read off from stable internal values. This is why "what do customers prefer" is an incomplete question. Preference is partly a property of the presentation.

Feedback and perceived progress

Interfaces also shape behavior through what they report back. Progress indicators increase completion, and the effect is sensitive to how progress is framed — a task shown as partly complete at the outset is pursued more persistently than an identical task shown as beginning at zero (Nunes and Drèze, 2006, on endowed progress).

This is a legitimate design tool when the progress is real. It becomes deceptive when the endowed progress is fictional, which is a good illustration of how a mechanism is neither ethical nor unethical in itself.

What this means in practice

Audit the interface for decisions that were made by default rather than by intent: what is first, what is largest, what is preselected, what requires the most effort to reach. Each of those is currently influencing behavior. The only choice available is whether that influence is deliberate and defensible.

References

1. Thaler, R. H., & Sunstein, C. R. (2008). Nudge: Improving Decisions About Health, Wealth, and Happiness. Yale University Press.
2. Huber, J., Payne, J. W., & Puto, C. (1982). Adding asymmetrically dominated alternatives: Violations of regularity and the similarity hypothesis. Journal of Consumer Research, 9(1), 90–98.
3. Simonson, I., & Tversky, A. (1992). Choice in context: Tradeoff contrast and extremeness aversion. Journal of Marketing Research, 29(3), 281–295.
4. Nunes, J. C., & Drèze, X. (2006). The endowed progress effect: How artificial advancement increases effort. Journal of Consumer Research, 32(4), 504–512.
5. Johnson, E. J., Shu, S. B., Dellaert, B. G. C., et al. (2012). Beyond nudges: Tools of a choice architecture. Marketing Letters, 23(2), 487–504.