Video games frequently feature 'open world' environments, designed to motivate exploration. Level design patterns are implemented to invoke curiosity and to guide player behavior. However, evidence of the efficacy of such patterns has remained theoretical. This study presents an empirical study of how level design patterns impact curiosity-driven exploration in a 3D open-world video game. 254 participants played a game in an empirical study using a between-subjects factorial design, testing 4 variables: presence or absence of patterns, goal or open-ended, nature and alien aesthetic, and assured or unassured compensation. Data collection consisted of in-game metrics and emotion word prompts as well as post-game questionnaires. Results show that design patterns invoke heightened exploration, but this effect is influenced by the presence of an explicit goal or monetary compensation. There appear to be many motivations behind exploratory behavior in games, with patterns raising expectations in players. A disposition for curiosity (i.e. 'trait curiosity') was not found to influence exploration. We interpret and discuss the impact of the conditions, individual patterns, and player motivations.