Processing Approaches in Perception

How exactly do we identify an object? Do we recognise a dog, for instance, because we have first recognised its individual features -- its furry coat, its four legs, its eyes, its ears -- and then built up to the recognition of the whole animal? Or do we instead first recognise these individual parts because we have already identified the whole animal as "a dog"? Psychologists describe these as two contrasting processing approaches.

The idea that the recognition process begins from the individual parts, which then serve as the basis for recognising the whole, is known as bottom-up processing. The idea that the recognition process instead begins from the whole, which then leads to the identification of its various individual components, is known as top-down processing. The bottom-up approach places its emphasis squarely on the features of the stimulus itself, and treats perception essentially as a process of mental construction built up from those features. The top-down approach, by contrast, places its emphasis on the perceiver, and treats perception as a process of recognition or identification of stimuli, guided by the perceiver's existing knowledge a …