Top-down and bottom-up processing

Bottom-up processing is an explanation for perceptions that start with an incoming stimulus and working upwards until a representation of the object is formed in our minds. This process suggests that our perceptual experience is based entirely on the sensory stimuli that we piece together using only data that is available from our senses.

In order to make sense of the world, we must take in energy from the environment and convert it to neural signals, a process known as sensation. It is in the next step of the process, known as perception, that our brains interpret these sensory signals.

Bottom-Up vs. Top-Down Processing

How exactly do people process perceptual information from the world around them? There are two basic approaches to understanding how this sensation and perception takes place. One of these is known as bottom-up processing and the other is known as top-down processing.

Bottom-up processing can be defined as sensory analysis that begins at the entry-levelwith what our senses can detect. This form of processing begins with sensory data and goes up to the brain's integration of this sensory information. Information is carried in one direction starting with the retina and proceeding to the visual cortex.

This process suggests that processing begins with a perception of the stimuli and is fueled by basic mechanisms developed through evolution. Unlike top-down processing, bottom-up processing is purely data-driven and requires no previous knowledge or learning. Bottom-up processing takes place as it happens.

For example, if you see animage of an individual letteron your screen, your eyes transmit the information to your brain, and your brain puts all of this information together.

How Bottom-Up Processing Works

The theory of bottom-up processing was introduced by psychologist E. J. Gibson, who took a direct approach to the understanding of perception. Rather than being dependent upon learning and context, Gibson felt that perception was a what you see is what you get process. He argued that sensation and perception are the same things.

Because Gibsons theory suggests that processing can be understood solely in terms of environmental stimuli, it is something referred to as the ecological theory of perception.

Bottom-up processing works like this:

1. We experience sensory information about the world around us, such as light levels from our environment.
2. These signals are brought to the retina. Transduction transforms these signals into electrical impulses that can then be transmitted.
3. Electrical impulses travel along visual pathways to the brain, where they enter the visual cortex and are processed to form our visual experience.

This approach to understanding perception is an example of reductionism. Rather than looking at perception more holistically, including how sensory information, visual processes, and expectations contribute to how we see the world, bottom-up processing breaks the process down into its most basic elements.

Real-Life Applications

You can compare how bottom-up processing works to how top-down processing works by considering examples of how each process works. Imagine that you see a somewhat obscure shape. If you saw the shape on its own, using bottom-up processing, you might immediately perceive it as a capital letter B.

Now if someone were to place that image next to other context clues, such as next to the numbers 12 and 14, you might them perceive it as the number 13 rather than a capital B. In this case, you use top-down processing to interpret the visual information in light of surrounding visual cues.

Visual Illusions

While the two processes are often presented as competing theories, both play an important role in perception. The experience of visual illusions, for example, can illustrate how bottom-up and top-down processes influence how we experience the world.

You have probably seen a number of visual illusions where random ink blobs initially just look like ambiguous shapes, but after a moment begin to look like a face. If we used only bottom-up processing, these ink blobs would continue to look just like random shapes on paper.

However, because our brains are predisposed to perceive faces and because of top-down processes, we are likely to begin to see a human face in these ambiguous shapes.

Brain Disorders and Damage

Prosopagnosia, also known as face blindness, is a neurological disorder in which people are unable to recognize familiar faces, including their own. While other aspects of visual processing and cognitive functioning remain unaffected, people experience functional sensation but incomplete perception. Patients are able to perceive familiar faces, but not able to recognize them.

In this case, bottom-up processing remains functional, but a lack of top-down processing makes them unable to relate what they are seeing to stored knowledge. This demonstrates how important both processes are in shaping our perceptual experiences.

A Word From Verywell

Bottom-up processing can be extremely useful for understanding certain elements of how perception occurs. However, research has also shown that other factors including expectation and motivation (elements of top-down processing) can have an impact on how we perceive things around us.