What are 'perceptual constancies' and what part do they play in our perception of the world?
Guidance
For general guidance about what is expected in your essays for this module, see the general criteria.
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What Key Features Do I Look For?
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Please remember to avoid footnotes and to include an alphabetical list of 'References' which have been cited in the text (not a Bibliography of anything you have read for the essay). This list should include author's names, date, book titles (in italics), place of publication and publisher. Within the text always cite author's surname, date and page number. Double-space your text and number your pages. For more detailed notes on writing essays in this department, click here.
Advice for this particular assignment: To be sure that you understand the concept as well as you possibly can, consult several standard academic psychology textbooks (at least three) for this question - note both the similarities and the differences between the way different psychologists treat this concept. Note, however, that a good essay will involve consulting more specialist texts on the topic rather than just textbooks. Do not rely on standard dictionary definitions: 'perceptual constancy' is not 'perception' plus 'constancy'; it is not 'whatever is constant in perception'. Perceptual constancy is a psychological mechanism that stabilises relative shifts in the appearance of things (but find definitions for yourself from the psychology textbooks). Don't even begin to go from note-taking to essay-writing until you are sure that you understand what the concept is: if you don't understand it, no amount of waffle will help the reader to understand what you mean! Since this is a relatively technical topic, check with some friends that they understand what you have written - if they don't, your essay is not ready for submission. Remember that there are various kinds of perceptual constancy - for vision these include shape, size, speed, colour, light and position. You should write a little about several of these. You are not obliged to discuss 'object constancy' here (the persistence of objects, and parts of objects, when you can't currently see them). Focusing on particular examples will help you to make the concept clearer.
Perceptual constancy doesn't always work - sometimes it 'fails' or 'breaks down' - at such moments we become conscious that what might normally have seemed to be the same size, shape, brightness (etc.) is actually significantly different (because of distance, angle, lighting etc.). This gives rise to some striking illusions. Give some examples of instances when perceptual constancy fails. In such instances it is contextual factors that over-rule the usual constancies (e.g. where different surrounding colours make the surrounded colour seem different when it is in fact the same colour - the opposite effect of colour constancy). BEWARE: Do not offer - as examples of constancy - illusions which illustrate its breakdown! If you do, you clearly do not understand perceptual constancy and will lose marks heavily.
There are perceptual constancies for senses other than sight but it might be wise to indicate that, while you are aware of their existence, you will not explore this here because our focus is on the visual. Refer also to the role of familiarity - most often mentioned in the context of size as familiar size (we normally assume that familiar things are their usual size). Familiar shape comes into play in relation to the famous Ames Room, which you can discuss in relation to your main theme. You could argue, for instance, that in the Ames room, size constancy breaks down at the expense of shape constancy. Other than such closely-related issues, keep strictly to perceptual constancy - do not waste space on generalisations about perception or you will lose marks. I strongly suggest that you avoid philosophical books on perception at this stage - they are likely to confuse you.
Note also that this is an assignment for which the inclusion of relevant pictorial illustrations is likely to be an advantage. These should be inserted electronically into your Word document rather than cut-and-pasted in. You can scan such illustrations in from print sources, save them from disk-based sources, download them from online sources (such as my Powerpoint slides) or even create them from scratch in a graphics package. Use them to help you to make points more effectively. Label each one, 'Figure 1' etc. and add a caption.
Some suggested reading
See also chapters related to perception in general textbooks on psychology.
Note: Treat with extreme caution sources labelled with this symbol!
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