Metaphorical expressions appear once every twenty words in everyday language, and play a central role in communication. Some cognitive linguistic theories propose that understanding metaphorical expressions requires mappings from one conceptual domain to the other. My research uses Event-Related Potentials to examine the processing, the representation, and the cognitive processes used in the comprehension of conventional and novel metaphor mappings. The first study investigated whether metaphorical language was processed differently from literal language. It was found that conventional metaphors needed an initial burst of processing effort but such effort was quickly resolved, whereas novel metaphors took longer to integrate. The second study examined whether the processing effort required for understanding conventional metaphors was related to retrieving mappings between the involving concepts. It was found that such effort was reduced when readers were first exposed to another instance using the same mappings. The third study explored whether metaphors were understood via the basic mechanisms used in the process of comparison. It was found that both novel and conventional metaphors were processed more easily when readers first saw similes that overtly encouraged them to compare the two concepts. These findings have several implications. Understanding conventional metaphorical sentences requires some cognitive effort to retrieve the mapping representation between the involving concepts, and such retrieval can be facilitated by comparison thinking. Understanding novel metaphorical sentences requires cognitive effort much greater than the conventional ones in order to generate the mappings, and such meaning generation stems from a comparison process. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]