This study investigates the role of mental simulation in message formulation and grammatical encoding in two typologically distinct languages, English and Japanese. It examines relationships among physical motion, mental simulation, and sentence production, following the claims of Perceptual Symbol Systems (Barsalou, 1999) that people understand language by mentally simulating multimodal experiential knowledge, and that such simulation involves activation of our sensorimotor systems (Barsalou, 2007; Gallese, 2007). Specifically, it assesses whether speakers' embodied status, manipulated by motor activities, can influence message choice and word order. The relationship between motion and language production mechanisms was examined with four factors: language (English vs. Japanese), direction of prime action (toward-, away-, or neutral-motion), timing between motion and message formulation (motion before vs. after the onset of message formulation), and message status ("unconstrained message" vs. "constrained message"). An unconstrained message was one for which the relational meanings of two objects were under-determined: participants saw pictures of two objects and described an action involving those two objects. In contrast, in a constrained message, participants described a fixed event depicted by a sequence of pictures. The results reveal that regardless of language and message status, motion has an impact on the message planning process. In unconstrained utterances, motion drives people to produce sentences with a corresponding directional orientation: participants produced more "toward sentences" that implied movement toward the speaker's body after toward motions, while they produced more "away sentences" that implied movement away from their bodies after away motions, compared to those after neutral motions. Furthermore, the results in Japanese show that participants favor the word order that presents referents in an order consistent with the corresponding situation described in the sentence. Crucially, motion boosts the relationship between event language and word order. These results indicate that speakers are fundamentally responsive to embodied information that is activated through physical motion, regardless of presence or absence of relational meanings in the intended message, and regardless of the timing. Moreover, on-line, causal effects of simulation on event language and word order determination suggest that simulation is a critical part of our language that is cognitively grounded in embodied experiences. [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.]