Fundamentals of human perception: Short-term memory

We develop applications for people. Therefore, the basis of every good design is human perception. Various findings from psychology make it easier for us to process information in a way that it is easily understood, and to arrange elements so that they are easily grasped. To better understand human perception, we have launched a multi-part series. We start with short-term memory:


The 7 plus/minus 2 Rule of Short-Term Memory:

The human memory can be divided into 3 parts: the sensory memory, the short-term memory, and the long-term memory. These 3 parts of memory have different characteristics that have led to their classification as different instances of our memory. We will not go into long-term memory here, as it is not relevant to usability.

Our sensory memory stores elements for about 1 second before they move to short-term or working memory, or are discarded. Short-term memory stores content with a variable storage duration. The duration is variable because attention constantly turns to new information that needs to be stored in short-term memory. Unlike sensory memory or long-term memory, the storage capacity in short-term memory is significantly lower.

“There is a clear and definite limit to the accuracy with which we can identify absolutely the magnitude of a unidimensional stimulus variable. I would propose to call this limit the span of absolute judgment, and I maintain that for unidimensional judgments this span is usually somewhere in the neighborhood of seven. We are not completely at the mercy of this limited span, however, because we have a variety of techniques for getting around it and increasing the accuracy of our judgments” (Source: )




In 1956, American psychologist George Armitage Miller described the fact that a person can only process 7 plus/minus 2 information units (chunks) in short-term memory at the same time. The size of short-term memory is genetically determined and cannot be increased through training.

What does this mean for me as a UX/UI designer?

The human short-term memory cannot process more than 7 information units. For this reason, we keep the number of information on a page as low as possible and combine related information units into chunks. This keeps the cognitive workload low. In an online store, we provide a maximum of 5 different price options. And the navigation structure also does not include more than 5-7 elements.


Paradox of Choice:

The phenomenon known as the “Paradox of Choice” was first described by American psychologist Barry Schwartz in his book of the same name. B. Schwartz argues that too much information can be overwhelming. If we have 24 different types of jam in front of us, then it is extremely difficult to decide on one. However, if there are only 3 different types of jam in the store, the decision is much easier. We can adapt this principle to human-machine interaction: On the one hand, we want as much choice as possible, but on the other hand, we are more likely to make a decision when the choice is smaller and we can more easily work out what the best option is. Remember: Short-term memory processes only 7 plus/minus 2 elements at the same time. If our choice is larger, we have an increased cognitive workload. The user must quickly find a solution to achieve their desired goal. However, if they first have to work through various variations that occupy their short-term memory for a long time, it becomes more challenging.


Outlook on the Future:

This was the first part of the series “Fundamentals of Human Perception”. We have looked at short-term memory, as well as the “Paradox of choice”.