UX Basics: 5 Design Principles That Affect Shopper Behavior

Great user experience (UX) design keeps customers coming back. Poor UX pushes them straight toward competitors.

According to research from PwC, 53% of consumers now say that a seamless customer experience is the bare minimum they expect from brands. What’s more, 29% of survey respondents say they stopped buying from a brand because of poor customer service online or in person.

For brands and retailers, this begs the question: What makes a “good” UX? Here’s a breakdown of five design principles that affect shopper experiences, and what brands can do to ensure experiences align with customer expectations.

Principle 1: The Aesthetic Usability Effect

First identified by researchers Masaaki Kurosu and Kaori Kashimura in their 1995 paper, “Apparent usability vs. inherent usability,” the aesthetic usability effect is simple: If UX designs are aesthetically appealing, users believe they work better than those that are visually unappealing.

The aesthetic usability effect is tied to humans’ preference for pretty things. One common example is the Halo Effect.

As discussed in a research paper from the Encyclopedia of Tourism Management and Marketing, the Halo Effect is “the tendency of individuals to extrapolate their impressions of an aspect of an object to other aspects of that same object.” In other words, a physically attractive person is often deemed to have other positive qualities based solely on the fact that they’re attractive.

The aesthetic usability effect applies this same reasoning to UX. Websites and apps that are easy on the eyes are assumed to be more functional than their less-pretty counterparts.

What’s more, minor usability issues are often chalked up as outliers rather than inherent characteristics.

What This Means for Brands: Prioritize Function and Form

Sites that look great won’t cover up usability shortcomings, but aesthetics do play a key role in how users perceive the digital purchasing experience.

While function should be the foundation, it’s worth taking the time to ensure ecommerce sites and mobile apps look great to users.

Principle 2: Choice Overload

Also known as the Paradox of Choice, choice overload is the inverse relationship between more choices and the ability to decide.

Consider a customer selecting among three products that perform similar functions but offer different feature sets and have different price points. In this case, the comparison process is relatively simple: Which single choice offers the best mix of value and performance?

Now expand the pool of potential products to 10, 50, or 100. More options mean fewer differentiating factors, in turn making it harder for customers to decide. From a UX perspective, providing prospective buyers with too many options simultaneously can lead to decision paralysis, in turn causing them to abandon purchases before they’re complete.

What This Means for Brands: Keep It Simple

Simplify the decision-making process by providing ways for customers to narrow their search. These include comparison charts for similar items, the ability to filter product results by price point, features, or shipping time, and intelligent on-site search tools that return curated results.

Consider data from Salsify’s “2026 Consumer Research” report, which found that 39% of customers are now comparing prices more carefully before making a purchase.

While more choices provide more context for cost, too many choices can create frustration that negatively impacts the user experience and damages their overall perception of price vs. value.

Principle 3: Jakob’s Law

Developed by Jakob Nielsen of the Nielsen/Norman Group, Jakob’s Law states that customers want your site or app to work the same as the sites they already know.

This is because humans are creatures of habit. As noted by the Psychology of Habit, published in the Annual Review of Psychology, “People tend to repeat the same behaviors in recurring contexts.”

These contexts can be identical — for example, a person who gets up and brushes their teeth at the same time every morning — or they can be similar, such as a prospective customer who compares products across multiple apps.

This similar context leads to transferable expectations. If most sites contain quick search functions and high-quality product videos, customers expect these same features on all sites. Failure to deliver on familiar experiences can lead to a negative user experience and the loss of a prospective customer.

What This Means for Brands: Don’t Reinvent the Wheel — Improve It

Here, market research makes the difference. The more brands know about what other companies are doing, and how they’re doing it, the better positioned they are to build familiar experiences.

Consider the rise of second-generation chatbots capable of parsing consumer context. As these solutions become the norm, customers will expect these interactions as part of any user experience.

According to Salsify’s upcoming “2026 Holiday Pulse Report,” 16% of shoppers plan to use AI chatbots and shopping assistants to find gift ideas this year, up from just 9% in 2025.

By offering a similar experience on-site, brands can make it easier for customers to narrow down their search and find the perfect present.

Principle 4: Peak-End Rule

The Peak-End Rule was explored in a 1993 research report published in Psychological Science, “When More Pain is Preferred to Less: Adding a Better End.”

It argues that individuals don’t remember entire experiences. Instead, they most clearly recall how they felt at the event’s most intense moment — the “peak” — and how they felt at the end. In the original experiment, participants were asked to submerge their hands in 57 ºF water for 60 seconds.

They were then asked to do the same, and then keep their hand in the water for an additional 30 seconds as the temperature was raised from 57 to 59 degrees. When asked which experience they would repeat, participants chose the second, despite the longer exposure.

Researchers theorized that this was because the end of the second trial was less uncomfortable, creating a more positive association. In the first trial, both the peak and the end were the same — unpleasant.

What This Means for Brands: Reduce Friction and Stick the Landing

Users are more prone to remember negative experiences than their positive counterparts. For example, a company that sells great products but has a terrible website may see reviews for its awful online experience, but find very few reports of its high-quality goods.

To counteract this, brands must focus on two key areas.

First, create experiences that offer minimal friction. This could be as simple as a link on a social media page advertising a new product release.

Instead of taking customers to a generic landing page, this link should go directly to the product detail page (PDP) of the specific items. Given that 73% of Gen Z and 67% of millennials now use social media as their top product discovery channel, these streamlined experiences are essential.

Second, ensure customers leave on a high note. This could take the form of a special offer or discount, or a post-purchase follow-up containing detailed tracking information that keeps customers in the loop.

Principle 5: Serial Position Effect

The Serial Position Effect was proposed by German psychologist Hermann Ebbinghaus in 1913. It states that the first and last items in a series are the most easily remembered, while those in the middle are often forgotten.

Ebbinghaus used a series of words shown to participants every two seconds. After the series was complete, participants were asked to immediately recall the list. Results show that words at the end of the series were best remembered, those at the beginning were well remembered, and those in the middle were remembered the least.

What This Means for Brands: Start Strong and Finish Stronger

Lists are common on ecommerce sites and mobile apps, including lists of products, services, or prices. All are relevant to brand success, but some are more important than others.

Important items need to come first and last. Consider a product list that contains a company’s best-selling item, the newest version of the item, and items in the category that sell steadily but never sell out.

In this case, the new item should go at the front of the list, while the most popular item goes at the end. Because these items are the most remembered, they’re the most likely to be purchased, allowing brands to subtly influence the customer decision-making process.

UX Basics: The Only Constant Is Change

Consumer expectations are evolving — 70% of executives asked by PwC say that customer expectations are outpacing their ability to adapt. This is the reality of digital experiences. As personal mobile technology becomes faster, simpler, and more reliable, customers have less patience for poor UX that leaves them confused or frustrated.

The impact of UX becomes even more pronounced when brands consider the three-shelf model. While 69% of shoppers still prefer in-store shelves, 68% now prioritize digital shelf shopping.

Interestingly, 67% now start their journey online but finish purchases in store, a phenomenon known as “webrooming.” The result is a new reality where the digital user experience can impact both online and in-store purchases.

Bottom line? UX design can make the difference between consistent conversions and customer churn. By applying the principles above, brands are better positioned to deliver positive experiences and drive product purchases.