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The psychology behind user behavior

When it comes to improving any experience for users it’s important to understand how individuals form decisions. While we’d all like to think we’re rational decision-makers, the reality is very different. By understanding common biases and what influences human behavior we can help users understand what your site is offering and make the decision-making process quick and easy. 

What are heuristics?

A heuristic is a psychological term for a type of mental shortcut the brain uses to make decisions quickly, with low cognitive load. These psychological strategies allow people to move through the decision-making process without having to stop to process the “why” behind every action. Often, these shortcuts can lead to biases that influence behavior. 

And we can’t talk about heuristics without mentioning Jakob Nielsen. Nielsen developed a list of 10 heuristics that relate to the usability of digital interfaces; 

  1. Visibility of system status
  2. Match between system and the real world
  3. User control and freedom
  4. Consistency and standards
  5. Error prevention
  6. Recognition rather than recall
  7. Flexibility and efficiency of use
  8. Aesthetic and minimalist design
  9. Help users recognize, diagnose, and recover from errors
  10. Help and documentation

Though Nielsen compiled a list of heuristics to use as a rule-of-thumb for interactive design, there are many more heuristics based on psychology that inform decision-making. From social proof and pattern recognition to feedback loops and visual cues, there are heuristics that explain how people make decisions in every situation. 

For this article, I’ll focus on five common heuristics and explain ways you might form hypotheses around such principles to test their effect on your users. Many were postulated by Amos Tversky and Daniel Kahneman in the 1960-70s. Their work focused on the biases and failures in rationality when humans make decisions. Their first joint paper, "Belief in the Law of Small Numbers" covered eleven "cognitive illusions" that affect human judgment.

Five common heuristics

1. Affect 

When people make decisions they are heavily influenced by their emotions. Researchers Finucane, Alhakami, Slovic, and Johnson found that when users are in a positive emotional state, they are more likely to perceive an activity as having high benefits and low risks. This was found to be true even when “it was logically not warranted for that situation.” 

The implication of this heuristic is that if we can influence a positive emotional response via the experience, design, or copy of a website, that may alter that person’s judgment with respect to the perceived benefits and risk. 

One great way to incorporate this heuristic into web design is by using social proof. For example, using testimonials creates a positive emotion for the user based on the experience of another. Furthermore, the social proof includes an image of the user, which validates the testimonial and creates a humanistic connection. 

Example of social proof from Procore

2. Anchoring 

Not only do we make decisions based on past experiences, we make decisions based on the first information we learn in a given situation. This first piece of information is then used as an “anchor” to compare additional information, especially when it comes to price. For example, if you are in the supermarket looking to buy a bottle of wine and the first bottle you see costs $50 and the next two bottles are $35 and $30, then the latter two seem more reasonable, even if they are above the usual cost of a bottle of wine. 

If your team have used the affect heuristic from above, they’ve created a positive emotional experience when a user lands on your website. Now the user is ready to buy, they need to make a decision based on price comparison.

Typically most businesses order pricing tiers from lowest to highest. This can lead to bias if anchoring occurs; users may be heavily influenced by the first information they receive and go on to view the higher price options less favorably. Using this anchoring decision shortcut, you can experiment by switching the order to highest to lowest, with the middle option pre-selected. In this situation, the lower prices look like a saving compared to the first, more expensive option. The hypothesis being that this pricing order would lead to more users selecting the middle price point due to the higher initial anchor price.  

Example from Codecademy

3. Representative 

The representative heuristic is a mental shortcut, where we make a decision or judgment based on our most representative mental prototype or schema - formed by previous experience or learning. It’s this heuristic that leads us to make stereotypes. 

In our context, users may be presented with a product they aren’t familiar with, and thus call on their own mental examples of a similar product or situation to represent that product. For example, Bully Max dog food. 


By conducting a heuristic analysis of the site it was apparent that the dog depicted on the original product packaging evokes a specific representation - this is food for beefy, mean dogs. This representation from potential customers wasn’t one the business wanted. It led to testing different images of dogs to show customers that Bully Max is for all dog breeds who want to be healthy, not just dogs who look like bodybuilders.

4. Availability

The availability heuristic allows people to quickly arrive at a conclusion based on a recently related, or easily recalled example of the situation. Since these are more readily available in your memory, you will likely judge their outcomes as being more common or frequently occurring. 

For example, when deciding to travel by airplane, people may recall how difficult it was to get through airport security or how their last flight was canceled 3 times before they could get home. If these are the available memories related to flying, it may lead people to overestimate the likelihood of this experience happening again and they may decide not to fly. Availability can lead to false judgments because they’re based on such subconscious biases. 

Delta uses an understanding of this heuristic to its advantage. They allay these fears by addressing them transparently on their homepage, thus challenging the available memory users might have.

Delta webiste

5. Scarcity 

The idea behind scarcity is that the more difficult it is to obtain an item, or if urgency is required to obtain it, the more people desire that item. Users assign more value to the item once it seems exclusive. Because so many people have already bought the product, it must be good, right? This is how limited edition or low stock items work for ecommerce websites: 

Nordstorm website

Though the item is not on sale, the fact that there is only one left is more intriguing than a product that is readily available and thus leads users to want to make a purchase with urgency. 

How should you apply heuristics?

With as many distractions as people encounter these days and the short attention span that occurs when browsing the internet, it’s important to help people make decisions quickly before they lose focus. It’s imperative for businesses to have their value understood immediately to maximize their conversions. After all, if you can’t prove value quickly then users are just a google search away from purchasing from someone else. 

The heuristics highlighted in this article only scratch the surface of the cognitive biases that occur in decision-making. But it's important not to simply apply a list of heuristics. It’s only by conducting research you can begin to identify the types of heuristics that apply to your specific audience. Once you’ve identified what areas of your site need improvement and what biases might be at play can you begin to hypothesize how to combat them and then experiment to observe if your solution has the desired effect.  

It’s also important to understand that emotion is a huge motivating factor for making decisions. Though there are plenty of marketing and design-savvy people scrolling through the internet, heuristics are always at play in their subconscious. Tapping into these heuristics to help users make decisions quickly will improve usability and conversion on your site.

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