Bottom-up processing starts with sensory information retrieval from the external environment to develop perceptions depending on the current sensory information input. Top-down processing involves interpreting incoming data based on past experiences, knowledge, and expectations.
In bottom-up processing, you don’t need any learning, and perceptions rely solely on new stimuli from the present environment. This means a perception’s driving force is the stimulus you’re currently experiencing in your external environment.
In top-down processing, past experience, expectations, and knowledge are crucial in building perceptions regarding new stimuli, so a perception’s driving force is your previous experience, knowledge, and expectations. This article explains the differences between bottom-up and top-down processing.
How bottom-up vs. top-down processing works
In bottom-up, the processing is done in one direction, starting from the retina to the striate cortex. Every visual pathway’s subsequent stage carries out more of the input’s complex analysis. Bottom-up processing works as follows:
- It begins with a sensory input analysis, such as light patterns
- This data is sent to the retina. Then, transduction converts the information into transmittable electrical impulses
- The electrical impulses are transmitted to the brain through visual pathways, entering the visual cortex and getting processed to create a visual experience
In top-down processing, the brain uses what it already knows to bridge the gaps and predict what’s next.
Examples of bottom-up processing
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Road sign interpretation
Road signs use various affordances to show direction and speed requirements. When driving, you aren’t operating from the top down; you’re sensing the markings on the road and roadside to ascertain where you’re going and your speed.
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Prosopagnosia
A patient with prosopagnosia doesn’t apply top-down processing to recognize people. They can handle what they see when looking at someone’s face. The patient can determine whether a person has a crooked nose, blue eyes, or freckles. However, they can’t decide whether or not they’ve seen the face before or who it is.
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Blind taste test
A blind taste test can be used in a game show or cook-offs to guess what you’re eating. While you might have clues regarding what you’re about to taste, bottom-up processing comes in handy to help you determine what’s in your mouth. Your taste buds transmit sensory details to the brain to help it figure out what you’ve just eaten.
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Sensing a far-away fire
When nothing seems unusual in the forest, you might suddenly hear popping sounds. You could even perceive a faint smoke smell and later start feeling parts of your body exposed to heat. These signs can help you know that there’s a fire close by, giving you time to run away, especially if you’re thermophobia, or confirm if all is well.
Examples of top-down processing
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Stroop effect
You might be shown different colored words to identify the ink color, not the word. According to top-down processing, this task might be difficult because individuals automatically recognize the words before thinking of their features.
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Typos
Since writing is a high-level activity, the brain can trick you into seeing what you feel or think should be in the message. It can fill in missing information and correct mistakes without you noticing. When writing a message to someone, you might proofread and hit the send button only to realize once it’s gone that it has errors.
Endnote
Bottom-up processing is crucial when trying to understand how specific perception elements occur. However, top-down processing factors like motivation and expectation can impact how you perceive things around you.