Compare and contrast theories of perception which emphasize top-down processing against those which emphasize bottom-up processing. How useful is this distinction in the study of perception?

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Compare and contrast theories of perception which emphasize ‘top-down’ processing against those which emphasize ‘bottom-up’ processing. How useful is this distinction in the study of perception?

As we look around us it is unlikely that we spend time consciously working out how we use our senses to discover and understand the world around us. We tend to understand the world holistically. Whilst sensation is the ability of our senses to distinguish and use certain energy sources, it generally agreed that perception involves the analysis of information received from our senses and its subsequent cognitive interpretation (Pike & Edgar, 2005). However, it is how this analysis occurs that has led to much debate. This essay will focus on some predominate theories of perception, that of JJ Gibson, Marr and the constructionist approach. Gibson’s theory is embedded in a bottom-up approach, in that perception is achieved from the stimuli received via the senses. Whereas the constructionist view is that perception does not occur from stimulus alone, top-down processing from prior knowledge is also required. Another view to understanding perception is to look at its goal, is it for action or object recognition (Pike & Edgar, 2005).  .

Whilst these theories appear polarized, I will argue that to take either a top-down or bottom-up approach is not necessarily a useful distinction and that current research to support a dual process approach.

A bottom-up strategy suggests that perception is achieved from information received from the senses (Pike & Edgar, 2005). Gibson argued that everything that is needed for perception can be found directly from the stimuli. He went so far as to postulate that no cognitive process or memory was required for a person act within the environment (Pike & Edgar, 2005). For Gibson the goal of perception was action as opposed to the constructionist view that concentrated on perception for object recognition. He suggested that we perceive the world around not as a visual picture but in terms of what use objects afforded us. His approach was that to really study perception it has to be ecologically valid (Pike & Edgar, 2005). For Gibson, it is the relationship between the observer and the environment that became the focus for perception. He termed the reflection of light from textured surfaces the ambient optic array and it is this combined with the position of the observer that was crucial to how we perceive and act in the environment (Pike & Edgar, 2005). Invariants are “picked up” in a changing environment from the optic flow. It is these invariants that Gibson uses to support his claim that everything that we need to perceive the world is found in the information from the stimuli.

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Fig 1 – Necker’s Cube (Pike & Edgar, 2005).

A criticism of Gibson and indeed bottom-up processing is that it fails to explain certain illusions such as the Necker’s cube (fig 1) where the cube can be seen from two perspectives. This, as proponents of top-down processing would suggest indicate that the stimulus is insufficient to perceive what is being observed. They would argue that there are cognitive processes at work that allow to perceive the two perspectives, with a hypothesis being formed and then changing when another presents itself. Gibsonian theory would suggest that the cube lacks any ...

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