Speakers' assumptions about the lexical flexibility of idioms

In three experiments, we examined why some idioms can be lexically altered and still retain their figurative meanings (e.g., John buttoned his lips about Mary can be changed into John fastened his lips about Mary and still mean "John didn't say anything about Mary"), whereas other idioms cannot be lexically altered without losing their figurative meanings (e.g., John kicked the bucket, meaning "John died," loses its idiomatic meaning when changed into John kicked the pail). Our hypothesis was that the lexical flexibility of idioms is determined by speakers' assumptions about the ways in which parts of idioms contribute to their figurative interpretations as a whole. The results of the three experiments indicated that idioms whose individual semantic components contribute to their overall figurative meanings (e.g., go out on a limb) were judged as less disrupted by changes in their lexical items (e.g., go out on a branch) than were nondecomposable idioms (e.g., kick the bucket) when their individual words were altered (e.g., punt the pail). These findings lend support to the idea that both the syntactic productivity and the lexical makeup of idioms are matters of degree, depending on the idioms' compositional properties. This conclusion suggests that idioms do not form a unique class of linguistic items, but share many of the properties of more literal language.