Metaphor is a fundamental mechanism of human cognition, and metaphorical linguistic expressions are pervasive in everyday conversations and written texts. The specificity and imageability of metaphors make them a perfect vehicle for conveying abstract or complex meanings in terms of more salient ones, and the lexicon of languages is rich in single words and multi-word expressions based on metaphor, such as idioms, phrasal verbs, idiomatic phrases, and collocations. Most speakers of a first language (L1) learn to understand metaphors and to make proper use of metaphorical expressions within their given linguistic community effortlessly, simply by being exposed to language in terms of real use, without engaging in conscious or intentional learning activities. For second language (L2) learners, conversely, metaphors represent a great challenge. On the one hand they are considered by some scholars as a sign of near-native mastery of a second language and an important learning goal. On the other hand, they hardly ever find a place in the language lesson where explicit teaching prioritises more frequent and rule-driven forms. One consequence of this is that these expressions are for the most part learned incidentally, and the second-language learner is faced with the difficult and exacting task of having to learn to use an enormous number of expressions. In this study, in order to investigate the mechanisms of comprehension and learning of metaphorical expressions in L2, a controlled experiment was carried out examining the influence of the L1 and of syntactic properties of L2 expressions on understanding and learning of metaphoric expressions.
