Principle of least effort
Our brains are sophisticated machines. They're can process complex patterns, and they regulate every aspect of our bodily functions. But even though we have complex minds, we don't want to think too hard or too much if we don't have to. If there are several ways to do something, we choose the one that's the least demanding. And this is often done without conscious thought. The experiences that we perceive as seamless. UI designs that are easy to use and don't require unnecessary thought are often considered great user experiences.
In the book "Thinking Fast and Slow," by Nobel Prize winner Daniel Kahneman, he discusses two systems that determine how our brains work. One that we control and one we don't. The first system allows us to make decisions with little or no mental effort. Most of these decisions are completely unconscious and automatic. For example, quick decisions you make by following your gut or your intuition. The second system, on the other hand, represents conscious, deliberate thought. This is what we use to analyze data, make big decisions, and solve problems. This system requires more effort, and is much slower than first.
Humans naturally prefer to use the first system because it's quicker and takes less effort. And we don't want to engage second system unless we really have to, because it's so cognitively demanding. This is what is called the principle of least effort. We like it when a product or service helps us find what we're looking for, easily accomplish our task, and achieve our desired result without making us think too hard.
As user experiences have improved, our expectations have also gotten higher. When tasks that should be easy and straightforward, like skimming a news article or finding the price on a product page, it becomes more demanding than we expect them to be. This causes users to look for another source that doesn't use the second system as much.
So what can we consider when designing UX? Simple, allow people to do as little as they have to, including thinking to achieve their goals. Make your website more scannable by using less text and adding more pictures. Show examples or explanations through pictures rather than text. Create clear and visible navigation with wording that is familiar like home, back, etc. Provide defaults and short cuts that cater to common work flows such as home screen. Make things that are clickable, look clickable and things that aren't, not. For example, make links have different visual states when hovered over. Give people a little bit of information and then offer the opportunity to learn more by clicking through. Most importantly, find out your users' needs so you don't overload your app or website with unnecessary functions, content and clutter. Design for their desired needs and work flows only.