Think about the last time you went on vacation. What do you remember?
Perhaps you remembered a particularly beautiful view from the top of a mountain after a long hike. Maybe you thought about an interesting exhibit you saw at a museum or a perfect morning on the beach with your family. You might also have pictured the moment when your last trip took a turn for the worse: maybe you thought of losing your passport or falling ill far from home. Whether the memories were happy or miserable, your overall impression of your last vacation likely featured a few particularly strong moments.
We remember experiences in our lives as a series of snapshots rather than a complete catalogue of events. Our minds quickly average the moments that most stand out in our memories to form our opinion of the past. The most emotionally intense points of an experience and the end of that experience are heavily weighted in how we remember an event.
Definition: The peak–end rule is a cognitive bias that impacts how people remember past events. Intense positive or negative moments (the “peaks”) and the final moments of an experience (the “end”) are heavily weighted in our mental calculus.
Understanding the rules of thumb that our minds use when storing information allows us to design more memorable products and to improve customers’ subjective opinions about a user interface.
The peak–end rule is grounded in research conducted by Daniel Kahneman and Barbara Frederickson. Their 1993 study found that the human memory is rarely a perfectly accurate record of events. The research team asked study participants to endure an uncomfortable but not dangerous experimental condition — study participants held their hands in a tub of cold water. (Maybe equivalent to using many an awkward website.) A series of short trials were conducted; participants changed which hand was submerged between trials and alternated the starting condition. The experiment consisted of three rounds:
- Round 1: 60 seconds at 14 degrees Celsius (57 degrees Fahrenheit)
- Round 2: 60 seconds at 14 degrees Celsius followed by 30 seconds at 15 degrees Celsius (59 degrees Fahrenheit)
- Round 3: Option to choose between repeating Round 1 or Round 2
The most logical choice would have been to repeat Round 1. Water is still unpleasantly chilly at 15 degrees Celsius, so it would be rational to choose 60 seconds of discomfort instead of 90 seconds. As it turns out, the slightly less uncomfortable final 30 seconds of the experiment changed how people perceived the entirety of Round 2. 80% of the study participants preferred Round 2 and chose to repeat that condition in the final trial.
A small improvement near the end of an experience radically shifted people’s perception of that event.
The Peak–End Rule in UX
In psychological studies and in product design, small changes have a large impact on people’s recollections. When designing interfaces and experiences, pay attention to the most intense points of a typical user journey (the “peaks”) and the final moments (the “end”).
Creating Positive Peaks
Conversations about UX often focus on the frustrating aspects of digital products, but there are many ways in which well-designed experiences make our lives easier. Elements that highlight moments of convenience, comfort, and even delight can transform a pleasant experience into a truly memorable one.
A bright color, an icon, or a lively illustration at the end of a successful interaction can solidify a good experience in your users’ memories. For example, Duolingo is an educational app that gamifies the process of learning a language. Its playful and conversational interface encourages users throughout its interactive lessons, enhancing an already positive impression.
Learning a new language is rewarding in and of itself, but Duolingo reinforces the intrinsic pleasure of the activity. The app affirms those successes, enhancing the feeling of accomplishment that comes with answering questions correctly.
Consider the most rewarding points in a typical journey for your users. What emotional payoffs already exist in an average session? Does your site offer answers to difficult questions? Does your app make a time-consuming process more convenient? Does your company offer a service that is substantially more affordable than its competitors? Identify the moments when your product is most helpful, valuable, or entertaining and design to make those moments even better.
The Impact of Negative Peaks
People remember negative experiences more vividly than positive ones. Moments of confusion and frustration also act as “peaks” in the peak–end rule — they are emotionally charged and have a substantial effect on the impression that users will later recall.
In a recent usability testing session we observed how people interacted with the website of a popular household-appliance company. The site had a primary-navigation interface that one study participant found particularly difficult. She clicked carefully through a menu with three levels of categories. Moving the cursor away from a specific target area caused the menu to close or to show a different section. Her comments quickly became more and more negative: at first she said “oops!” and then noted that “every time I [move the mouse] it erases the previous dropdown.” She then commented that the menu “disappears too quickly” and said “see, this is frustrating.”
The participant continued to interact with the site, later using a map to find a retailer that sold the company’s appliances. Her earlier negative experience with the menu had a strong effect on how she described the site at the end of the session. She again mentioned how frustrating she found the navigation and said that she would be inclined to investigate products offered by other companies because “I’m not really a brand-compliant person.”
Remember that online your users have many options available to them. A search engine and the websites of your competitors are always seconds away. Finicky menus, illegible text, and intrusive advertising make your users’ goals hard to complete. This difficulty creates a powerful emotional impression that is just as memorable as the positive “peaks” which foster goodwill among your users.
The Last Impressions
Last impressions are lasting impressions. When we remember an episode in the past, the most recent events are activated quickly in our memories. Ensure that your users’ experience of your product concludes on a high note.
The power of the last impressions in UI design is well illustrated by progress indicators: the HCI literature shows that, if a progress indicator speeds up towards the end, the process is judged to have been faster than if the speed of the progress indicator was constant.
But it’s not just microinteractions that can benefit from great last impressions. In TurboTax, the arguably complex flow of filing income taxes ends with a screen that celebrates the end of the process, acknowledging and enhancing most users’ sense of relief.
The application embraces the natural end point of the experience. It does not attempt to overstay its welcome in users’ lives through content hooks or attempts to upsell other products. This human and humorous design ends the user journey on a positive note.
When it comes to bidding users a gracious goodbye, TurboTax is the exception rather than the rule. Many sites prioritize clicks and conversions over long-term customer loyalty. We caution designers against using “please-don’t-go” pop-ups that that beg users not to leave a site. These interface elements irritate users and contribute to a negative impression of the site later on.
Consider Edge Cases
The emotional peaks of an online experience often occur in places where designers least expect them. Consider unlikely events that will negatively impact the usability of your product. Technical difficulties, server outages, and unavailable content will abruptly end an interaction with your site. Reaching a sudden dead end is so unpleasant and so unexpected that it will make a strong impression.
Your design can guide your users through disconnections or can add to the frustration of an already confusing event. Spotify, a popular music-streaming service, recently encountered difficulties with its servers. During that time some features were unavailable. Some users were unable to reset their passwords, and when they tried to do so, they were presented with an unusual error message.
The interface text did not explain the problem. It only said This feature is currently unavailable — leaving the user with no way to solve the problem and no idea when service will resume. The red box signals a need for urgent action by the user, when there is in fact no such action available. Users had no choice but to leave the site and “try again later.”
Instead of the satisfying conclusion seen in the examples from TurboTax and Duolingo, this example features a frustrating sudden stop in the online experience. The visually jarring design combined with the unexpected disruption of service creates an unpleasant and memorable “end.” Errors, downtime, and disconnections are currently an inevitable part of the internet as we know it. Designers can’t solve every problem and certainly should not be blamed for every bug that appears. However, we are responsible for minimizing the disruption to our users’ lives when technical difficulties arise. Explain what the problem is and offer a reasonable estimate for when that problem will be resolved. Ensure that your interface does not blame the user when the source of the problem is a disruption in service.
Our minds are efficient and economical with how they store information. We remember our past in snapshots that focus on points of intensity and on the last impression of an event. Designing with attention to detail around the important moments of the customer journey, with particular emphasis on the last step, allows you to build digital products that are worth remembering.
Harrison, Chris; Amento, Brian; Kuznetsov, Stacey; Bell, Robert. (2007). "Rethinking the Progress Bar”. Proceedings of the 20th Annual ACM Symposium on User Interface Software and Technology. (pp. 115-118).
Kahneman, Daniel; Fredrickson, Barbara L.; Schreiber, Charles A.; Redelmeier, Donald A. (1993). "When More Pain Is Preferred to Less: Adding a Better End". Psychological Science. (pp. 401-405).