Essential Psychology: A Concise Introduction, (2010). Ed: Philip Banyard, Mark N.O. Davies, Christine Norman & Belinda Winder. SAGE Press, London

Perception is the apparently holistic experience of the external world. That is, perception seems to provide us with experience of a reality that is integrated and complete when , for example, we look around us, watch television, talk or eat. Yet, intriguingly, perception does not produce an exact copy of the physical world: rather, perception involves a mental re-creation. It is not an accurate representation of our environment but an adequate one.

Perception is in effect a best guess, derived from an endless stream of external information (such as light and sound), and influenced by our arousal states (for example, whether we are alert, distracted or sleepy) and past experience (for example, we may interpret situations differently according to whether they are novel or familiar to us). Sensing and perceiving the world around us is a monumentally complex task that we do not fully understand, and yet somehow we do it, for the most part, effortlessly.

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Vision – Seeing

Vision dominates the human experience and we rely heavily upon it in our day-to-day interactions. It is thought that vision evolved to support motor action (Milner & Goodale, 1995)and, for typically developing humans, vision is the most immediate and commanding sense. It is commonly reported that over 80 per cent of all information about our external world comes through vision and abou 50 per cent of the cortex is given over to visual processing alone – as compared with about 10 per cent for audition (Snowden et al., 2006).

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On top-Down Approaches to perception

Visual illusions illustrate that perception is an active interpretive process. They work because we are trying to make sense of the visual information, even though the specific cause is different from one illusion to another and there may be more than one mechanism at play.

The constructivist approach is important in showing that knowledge and memory can and do influence perception.

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Summary

At present there is no single general theory of perception. Matlin and Foley (1992) argue that perception works because (1) the sensory world is rich in information (there’s a lot of information out there), (2) human sensory systems are good at gathering information, and (3) high-level concepts shape (impose constraints on and determine) what we experience. Ultimately the brain and the rest of the nervous system have evolved to create a system that is best suited to extracting and filtering out what it needs to sense and perceive what is in the stimulus-rich world around us.

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It feels as though we experience and represent everything. In fact we do not do this. Instead we have evolved systems that extract what is necessary to interact with our world, and at best our representation of the world is adequate, even if it is not accurate. Human perception is not perfect and we do not fully understand it, but it works just fine…well, most of the time!