Читать книгу Introduction to Experimental Linguistics - Sandrine Zufferey - Страница 21

Whether for the purpose of studying production or comprehension, research can be categorized according to the general framework in which data collection takes place or, in other words, the experimental design. On the one hand, there are longitudinal designs, in which the same subjects are observed on several occasions, following varying time intervals. This type of design is generally used in studies where a variable cannot be manipulated, but its effect can be observed through time. For example, to study the influence of age on the ability to distinguish sounds between the different languages spoken in the environment of babies growing up in bilingual homes, one possibility would be to test the same bilingual babies at 2 months, 4 months, then 8 months old. Another example of longitudinal design would be the study of the relationship between language development and the development of theory of mind. In this case, language skills and individual differences in theory of mind could be measured in children aged 3 and a half, 4, and 4 and a half, for example.

The major interest of longitudinal studies is that they make it possible to observe changes in real time. However, they also have two significant disadvantages. First, such studies imply that participants must be tested on several occasions in relatively short periods of time. It is thus inevitable to lose participants during the study, due to motivation and availability reasons. Secondly, these studies generate significant costs, since it is necessary to find and then test people repeatedly, and above all, keep in touch with them and convince them to return to the following test sessions.

In order to work around these problems, cross-sectional designs observe different people, who are subjected to different conditions. To use the example of bilingual babies, instead of testing the same babies at different ages, we could simultaneously test groups of babies of different ages. This method would imply making a sort of picture of a situation at a given moment, which would offer indications on the relationship between age and sound perception in bilingual babies. Cross-sectional designs are typically used in quasi-experiments, where the independent variable is not manipulated.

When the independent variable can be manipulated, it is possible to allocate the participants to different conditions, in which manipulation can either be present or absent. Two types of experimental designs can be constructed in this case. In the first, the between-subject design, the participants only take part in one condition or the other. For example, to study the influence of reading goals on reading comprehension, one option would be to carry out an experiment in which a group of people reads a text in order to briefly summarize it, while another group reads the same text in order to answer questions about it. The performance of the two groups can then be compared during a recall task after reading the text. The results of such a task would certainly show that the second group performs better than the first group (as in Schmalhofer and Glavanov (1986), for example).

In the second type of experimental design, the within-subject design, also called repeated-measures design, the participants take part in all the conditions of the experiment. For example, such a design can be used in an experiment on the influence of word frequency on their processing time. In this case, each participant would see frequent words and infrequent words in order to cover all the modalities of the variable frequency. Among other things, this type of design makes it possible to control the external variables associated with the participants, given the fact that everyone falls under all conditions. Between-subject and within-subject designs each have advantages and disadvantages, which will be developed in Chapters 2 and 6. For the moment, the main thing is to remember that there are many ways to organize research and that experimental research may adopt different designs, depending on the conditions under which the participants are tested.