Writing a ‘describe and evaluate a theory’ essay Probably the commonest sort of essay question asks you to describe and evaluate one or more psychological theories/explanations of something. Evaluation is a difficult skill because it is multifaceted, so you’ll need to practise a lot before getting it right. You certainly need to get beyond the idea, held by many students, that evaluation amounts simply to listing pros and cons of something. The essay question you are attempting is this: Describe and evaluate one theory of perception (10 marks). Recall that before you start answering a question you need to ask yourself: 1. What topic am I writing about? 2. What do I have to do with my knowledge of this topic? This part should be easy by now. The topic is clear: Describe and evaluate one theory of perception. And so are the requirements. There are two: Describe and evaluate one theory of perception. Those are the question’s requirements then. What we must do now is work out how the marks are going to be awarded by the examiner. Recall that an essay is assessed on two main objectives: knowledge and understanding (AO1) and commentary, analysis, criticism and evaluation (AO2). On PSYB2 a ten mark essay can earn 5 AO1 and 5 AO2 marks. So we can work out that you need to: • Describe...one theory of perception. ‘Describe’ is an AO1 term meaning ‘give an account of’. You’ll be earning AO1 marks every time you show knowledge and understanding of a theory of perception by showing how it explains the process by which we perceive the world around us. • Evaluate...one theory of perception. ‘Evaluate’ is an AO2 term which means ‘arrive at a conclusion about the value of something through a consideration of its strengths and weaknesses’. So you will get AO2 marks for identifying positive and negative criticisms of a theory of perception, justifying them using either some evidence or an argument and then drawing an overall conclusion about the theory’s value to psychology. What should go into this answer then? The specification mentions two theories by name: Gibson’s theory of direct perception and Gregory’s constructivist theory of perception. However, there are others you are likely to come across.

So the material we could include here would be: • Theories of perception e.g. Gibson, Gregory, Gestalt theory, Cyclical theory (Neisser) You need to select a theory that you can describe in detail and about which you can identify plenty of strengths and weaknesses by examining: • Evidence that supports the theory; • Evidence that challenges the theory. What else is important? What about the question specifying ‘one theory’? This is obviously significant. If you described and evaluated two theories then you wouldn’t be answering the question the examiner set. In this case, both theories would be marked and you would get the higher of the two marks. But it still isn’t a good idea because (1) you’d waste lots of time describing another theory for no extra marks; and (2) your essay would contain irrelevant material, which would restrict your mark. There are many approaches to this question, but we’re going to write this essay about Gibson’s theory of direct perception. There are many different ways of evaluating but we’ll stick to the most important in science: using evidence to evaluate theory. The AO1 skill we’re practicing here is the skill of describing theories accurately and in detail. You’ll be doing this well when you can present, in your own words, an account of how J.J.Gibson explained the process by which we perceive the world. Here’s an example of how this might be done if we were writing about Richard Gregory instead: Gregory (1966) put forward a constructivist theory of perception. His main idea is that we don’t perceive the world as it really is; what we perceive is a mental model of the world constructed from the clues our senses give us. The senses convey limited information about what there is in the world. Our mind uses knowledge from our past experiences and other psychological processes to make sense of this limited information. Consequently our perceptions of the environment vary depending on what we have encountered before and our mental states of emotion, motivation and expectation. Our perception will change according to how we feel (e.g. happy or sad) what we want (e.g. food, drink) and what we expect to encounter. In Gregory’s theory what seems to be ‘really there’ is in fact only a hypothesis about what might be present in the world. The AO2 skill we’re practicing here is evaluating theories using research evidence. You’ll be doing this well when you can state a strength or weakness of Gibson’s theory and then justify it by using some evidence to show that the criticism is valid. For a good evaluation you’ll subsequently need to consider all the evidence you have discussed and draw an overall conclusion about the value of the theory. Here’s how it could be done for Gregory’s theory. Gregory’s theory is supported by evidence from perceptual set studies. For example, Gilchrist & Nesburg (1952) found that PPs who were hungry judged pictures of food to be larger and brighter than non-hungry PPs. This shows that how people’s internal state (motivation) influences their perception of the external environment, as Gregory’s theory suggests. It’s important that the examiner knows that you are evaluating and can follow your reasoning. This means you have to keep to the point. In the example above, only the key features of the evidence are described – not the whole aim, method, results etc. This allows the writer to keep the focus on evaluating the theory. You can also see several ‘AO2 phrases’ that key the examiner in to the fact that this is evaluation. Some useful ones are: • ‘This theory is supported by...’ • ‘A finding that challenges this theory is...’ • ‘Further support comes from...’ • ‘This shows that/suggests/implies...’ Note also how the writer brings the paragraph back to Gregory’s theory, making a clear judgement about why the theory is good in this respect. Many students neglect to do this, and their evaluation suffers as a result. So what should you put in your essay? This time we’re looking for you to apply three skills to an essay about Gibson’s theory: (1) describing the theory accurately and in detail; (2) describing studies in only their essential details; and (3) evaluating the theory using evidence. Your essay will be assessed using the criteria below. The first three are compulsory. If you’re confident with them you can have a go at the last. In order to do this you will need to do some additional thinking about the validity of the research studies you are using.

You will need to organise the essay to first explain the theory and then to consider evidence for and evidence against before drawing an overall conclusion, so the above grid isn’t an essay plan – it’s there to help you plan more effectively by ensuring you include all the material you need to address. IMPORTANT You must write a plan and submit it with your essay. If there is no plan your work is incomplete and will receive a mark of zero. The other way to get a mark of zero is to plagiarise. You are plagiarising if you copy from or paraphrase straight from a textbook, web site or other source without attribution. If you are using ideas from textbooks and research studies you must cite the name(s) of the author(s) and the date of publication. Plagiarism is a serious academic offence and if you do it at university you get thrown out. Essays that simply paraphrase the textbook, Wikipedia or whatever will be rejected and a mark of zero recorded.