Semantic categories across languages appear to reflect both universal conceptual tendencies and linguistic convention. To accommodate this pattern of constrained variation, many theories assume the existence of a universal conceptual space and explain cross-language variation in category extension as language-specific partitions of that space. Three studies presented here evaluate this account of semantic variation and conceptual structure in the domain of spatial relations. Study 1 supports the idea of universal conceptual structure underlying semantic variation by demonstrating that predictive structural constraint can be inferred from cross-language variation. Study 2 takes a cognitively grounded approach, measuring presumptively universal conceptual similarity directly rather than inferring it from language, and finds that semantic categories correspond to coherent conceptual categories. These results provide indirect support for the assumption of universality. When this assumption is tested directly in study 3, we find evidence for both cross-culturally shared spatial concepts and conceptual variation in line with semantic variation. Taken together, this work contributes new evidence suggesting a view in which universal and language-specific forces interact to shape both language and cognition: Universal concepts constrain semantic variation, and the semantic categories of a particular language modulate the availability of those concepts to speakers of that language. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]