What is the core difference between bottom-up and top-down processing?

The core difference highlighted in the response is that top-down processing involves the use of prior knowledge and experiences to interpret and understand sensory information, while bottom-up processing relies purely on the sensory input itself without the influence of existing knowledge or expectations.

In top-down processing, the brain applies what it already knows to make sense of incoming stimuli. For example, when reading a text with missing letters, one's familiarity with the language allows one to fill in the gaps, demonstrating how contextual knowledge shapes perception.

On the other hand, bottom-up processing starts with the raw sensory data—like lights, sounds, or textures—and builds up to a complete perception without assuming prior knowledge. An example of this would be recognizing a new object that you have never seen before, where your perception is formed solely based on the characteristics of the object itself.

This distinction is fundamental in understanding how perception operates: top-down processing uses a framework shaped by personal experiences, whereas bottom-up processing constructs perception from the ground up, starting with the sensory information itself.