People segment their continuous stream of experience into events, or temporal segments that have a beginning and an endpoint. But how are such event boundaries defined? Linguistic theories of event encoding draw a distinction between bounded events that are non-homogeneous, structured temporal developments leading to an inherent endpoint (e.g., "dress a teddy bear") and "unbounded" events that are homogeneous temporal entities with no inherent endpoint (e.g., "pat a teddy bear"). Previous studies have illustrated the importance of endpoints for event perception and memory. However, this work has only discussed events with a self-evident endpoint, and the internal temporal structure of events has not received much attention. In this dissertation, we fill this gap. We hypothesize that event cognition tracks boundedness, and the sensitivity to boundedness affects how individual temporal slices of events (such as midpoints or endpoints) are processed and integrated into a coherent event representation. In Chapter 2, we show that viewers are sensitive to event boundedness in a category identification task and distinguish it from event completion; furthermore, viewers identify bounded events more easily than unbounded events. The sensitivity to boundedness emerges even when viewers are prevented from encoding the events linguistically and thus does not depend on the online use of linguistic distinctions. In Chapter 3, we find that viewers react differently to interruptions at the end compared to interruptions in the middle of an event -- but only when perceiving events with a bounded structure; moreover, viewers are more disturbed by temporal disruptions of a bounded event compared to an unbounded event. Chapter 4 tests our hypotheses from a developmental perspective and shows continuity in mechanisms of event cognition. We demonstrate that 4-to-5-year-old children compute boundedness during event categorization and treat it as different from event completion. Furthermore, 4-to-5-year-olds evaluate interruptions at event endpoints vs. midpoints differently when exposed to bounded but not unbounded events. We conclude that event viewers are sensitive to foundational and abstract properties of event temporal structure. This sensitivity can emerge from an early age, support the acquisition of linguistic-aspectual distinctions, and scaffold the way children conceptualize and process their dynamic experience. [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.]