A 3-5Jean Piaget was a Swiss developmental psychologist and was the first scientist to undertake experiments based on the theory that children go through four stages of development, and that only when they have reached the necessary stage of development can they perform the most advanced forms of cognitive operation. One of his famous experiments involved children comparing the amounts of liquid held by containers of different shapes, but of the same volume. Even when shown that the same amount of liquid could be poured into both containers, many of the young subjects would still insist that one container was larger than the other. 6Piaget's interpretation of this was that the children were unable to perform the logical task involved in recognizing that the two containers, while different in shape, were the same in capacity. This is because their cognitive development had not reached the necessary stage. Other scientists, however disputed his conclusion. 1-7For instance, developmental psychologist Margaret Donaldson raised the possibility that the children were simply unwilling to participate in the experimenter's game. 8Some critics also point out that these experiments involve social situations in which personal interactions take place, and more could be involved than what Piaget had in mind. Piaget's experiments may not only be measuring the children's capacity for logical thinking-their understanding of the requirements and the abilities of the experimenters to communicate, and the children's willingness to comply with the requirements could make a significant difference to the outcomes.
B Comparable criticisms have been made in relation to other psychological and educational tests. 2For example, Ed Meehan, a child psychologist, points out how test questions may be interpreted in ways different from those intended by the researcher. In a language development test, children were presented with a picture of a medieval fortress, along with moat, drawbridge, and parapets. Below the picture were three consonants: D, C and G. The children were asked to circle the correct initial consonant for the name of the item in the picture. To select C below the picture of the castle would have been considered correct by the researchers, but many children unexpectedly chose D. When questioned afterwards as to what they thought the picture was of, many children said “Disneyland”. These children used the reasoning which the researchers expected, and yet arrived at the wrong substantive answer. The score sheet showing a wrong answer does not document a child's lack of reasoning ability; it only documents that the child indicated an answer different from the one the tester expected.
C This is an example of the questionable validity of the measurements on which the findings of quantitative research are based. 4Some, including for example Donaldson, regard these as technical problems that can be overcome by more experimentation. Other，however，including Meehan，believe them to be more than simply problems of particular experiments or tests, but rather serious threats to the validity of this kind of research on a broader level.
D At the same time questions have also been raised about the assumption built into the ‘logic’ of quantitative educational research where causes can be identified by physical and statistical manipulation of variables. Critics suggest that this fails to take account of the very nature of human social life, assuming it to consist of fixed, mechanical causal relationships, whereas in reality life involves complicated processes of interpretation and negotiation that do not necessarily have determinate outcomes. From this point of view, it is not clear that we can understand why people do what they do in terms of the simple sorts of causal relationships on which quantitative research focuses. Our actual social lives, critics suggest, are much more contextually complex and variable.
E 12These sorts of criticisms of quantitative educational research have motivated an increasing number of educational researchers to adopt more qualitative approaches in the last thirty or forty years. This group of researchers has generally rejected efforts to measure and control variables either experimentally or statistically. Quantitative research can take various forms which can be loosely termed 'case study', 'participant observation', 'unstructured interview'，'life history', 'discourse analysis' or 'ethnography' etc.
F 10-11Qualitative research has a strong emphasis on exploring the nature of particular educational phenomena, rather than setting out to test hypotheses about them. Qualitative researchers have a tendency to work with 'unstructured data': data that have not been coded at the point of collection in terms of a closed set of analytical categories. When engaging in observation，qualitative researchers therefore audio-or video-record what happens or write detailed open-ended field-notes, rather than coding behaviour in terms of a predefined set of categories，as would a quantitative researcher employing 'systematic observation'. Similarly, when interviewing, open-ended questions will be asked rather than questions requiring predefined answers of the kind typical, for example, of postal questionnaires. Qualitative interviews are often deliberately designed to be similar to a casual conversation.
G 9Typically, a small number of cases will be investigated in detail, rather than any attempt being made to cover a large number, as would be the case in most quantitative research, such as systematic observational studies or social surveys. The analysis of the data relies less on quantification and statistical analysis. It actually involves highly accurate interpretations of the meanings and functions of human actions, and mainly in the form of verbal descriptions and explanations.
