How do we understand metaphors?

This article is a review of the experimental research on metaphor. We describe briefly the concept of metaphor and present two main theories about metaphor: the comparison theory (or similarity theory) and the interaction theory. According to the comparison theory, a comparison of features between the two concepts involved in the metaphor is the fundamental process underlying the interpretation of metaphor. According to the interaction theory, a metaphor induces the emergence of features that are associated neither with the topic nor with the vehicle of the metaphor. In order to find arguments in favour of one or the other theory, we present the experimental results which were obtained using two kinds of methods : macroscopic methods including sentence completion, tasks, judgment tasks, and memory tasks; and microscopic methods which include lexical decision tasks, reading time, and functional imaging techniques. Macroscopic methods aim at describing what the characteristics of metaphors and apprehending the result of metaphor interpretation. Microscopic methods try to follow the comprehension of a metaphor. While examining data, a synthesis of main factors which have been investigated (similarity, comprehensibility, context) is presented. We conclude on the difficulty to favor one or the other theory, and the necessity to develop interdisciplinary research.