What Is Parallel Processing in Psychology?

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In cognitive psychology, parallel processing refers to our ability to deal with multiple stimuli simultaneously. One example is driving. When we drive a car, we don't focus on driving exclusively; we also listen to music, carry on a conversation with our passengers, and look for the name of the street where our destination is located.

Our ability to process different kinds of stimuli at once enables our brain to carry out all these tasks at once.

This article discusses the discovery of parallel processing, how it works, and the limitations of this brain function.


The concept of parallel processing originated around the same time as the concept of information processing, which came about with the invention of computers in the mid-twentieth century.

Psychologists used computers as a metaphor for the way the human mind works. This lead to the ascendance of cognitive psychology in the psychology field.

Information Processing

Information processing was a central tenet of classical cognitive science when it became popular in the 1950s and remains important to this school of thought today.

A cornerstone of information processing is serial processing, which is the idea that the brain can process only one stimulus at a time. From this perspective, information is processed through a series of stages. First, a stimulus is encoded, then it is processed by the brain, and finally, the individual settles on a response to the stimulus and generates it.

One of the criticisms of serial processing is that if we only dealt with one stimulus at a time, we would process information too slowly. And in fact, evidence suggests that parallel processing is possible.

Today most cognitive psychologists are still exploring the domains in which we rely on serial or parallel processing. Because the inner workings of the cognitive system are challenging to study directly, this work is ongoing.

How Parallel Processing Works

In parallel processing, we take in multiple different forms of information at the same time. This is especially important in vision. For example, when you see a bus coming towards you, you see its color, shape, depth, and motion all at once.

If you had to assess those things one at a time, it would take far too long. So instead, seeing them together enables you to quickly determine what you're seeing and make a decision about how to respond.

In this instance, parallel processing will enable you to recognize you need to get out of the way of the bus before it gets too close. So we're engaging in this process constantly, even though we're not conscious of it.

Parallel processing also relies on a combination of top-down and bottom-up processing.

  • Top-down processing involves using your experiences, expectations, and knowledge to make sense of your perceptions. So if you see an animal running toward you, top-down processing will enable you to interpret whether you're seeing your dog running to greet you or another animal running to attack you.
  • Bottom-up processing is the opposite. It doesn't use any previous knowledge to assess information. Instead, it begins when our senses take in the most basic aspects of a stimulus, then our brain uses that data to form a complete picture of the information.

While top-down and bottom-up processing may seem incompatible with one another, parallel processing relies on both at the same time to understand stimuli.

For instance, if you see a person jump off a pier and then hear a splashing sound, our senses may build a picture of the incoming data through bottom-up processing. In contrast, top-down processing of sight and sound enables us to use our knowledge to understand that we saw the person jump into a body of water. Thus, with parallel processing, we can efficiently process and understand the stimuli we take in.


While we use parallel processing all the time in our daily lives, many people are able to increase their ability to parallel process in specialized areas of their lives through practice.

For instance, people who type on a daily basis will soon become experts, and this will reduce the number of cognitive resources the individual must dedicate to typing to the point where this task may require minimal or no thought. This is called automaticity.

There are degrees of automaticity. For example, more experienced drivers will likely have an easier time performing other tasks like attending to the directions of a navigation system while driving than less experienced drivers.

Automaticity enables people to perform impressive feats of parallel processing. For instance, in one study, researchers had students practice reading for comprehension while at the same time writing down dictated words that they categorized for meaning.

The average person wouldn't be able to do this right away, but the participants learned to perform these tasks without difficulty over several weeks of practice. That's because writing down the dictated words became automatic and no longer drew participants' attention away from what they were reading.

Limits to Parallel Processing

While parallel processing has many advantages, it also has some important limitations. As a result, psychologists have long tried to determine how much information people can process in parallel.

Research has arrived at different answers, but in general, the takeaway is that there is likely a limit to how much information we can process simultaneously before we have to rely on other strategies such as processing information serially, which may be less efficient.

Parallel processing is also limited by what psychologists call serial bottlenecks in information processing. As a general rule, we only pay attention to the most salient information in our environment because if we paid attention to every single piece of information, we'd be overwhelmed.

However, without practice or great concentration, we can typically use a single cognitive system to process more than one piece of information at the same time.

For example, think about how difficult it is to rub your belly and pat your head simultaneously; a single cognitive motor system controls our hands. This makes it challenging to give processes that work in opposition to one another—like rubbing one part of your body and patting another—equal attention, and as a result, do them equally well.

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Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Cynthia Vinney, PhD
Cynthia Vinney, PhD is an expert in media psychology and a published scholar whose work has been published in peer-reviewed psychology journals.