GERNSBACHER, M.A., KEYSAR, B., ROBERTSON, R. R. W.,& WERNER, N.K. (2001). The role of suppression and enhancement in understanding metaphors. Journal of Memory and Language, 45, 433-450.

Participants read either a metaphorical prime sentence, such as That defense lawyer is a shark, or they read a baseline-prime sentence. The baseline-prime sentence was literally meaningful in Experiment 1 (e.g., That large hammerhead is a shark), and nonsensical in Experiment 2 (e.g., His English notebook is a shark). After reading the prime sentence, participants verified a target property statement. Verification latencies for property statements relevant to the superordinate category (e.g., Sharks are tenacious) were faster after participants read the metaphor-prime sentence than after they read the baseline-prime sentence, producing an enhancement effect. In contrast, verification latencies for property statements relevant to only the basic-level meaning of the vehicle and not the superordinate (e.g., Sharks are good swimmers), were slower following the metaphor- versus the baseline-prime sentence, producing a suppression effect. As Glucksberg and Keysar’s (1990) class inclusion theory of metaphor predicts, the enhancement effect demonstrates that the vehicle of a metaphor stands for the superordinate category of the vehicle, and the suppression effect demonstrates that the metaphorical vehicle does not stand for its basic-level meaning.