Li, MengyingIn this thesis, I examine sedentary and screen-based activities among older adults, aim- ing to offer insights for designing effective behavior displacement interventions. While displacement represents a potentially effective intervention in reducing sedentary behavior, research in this area has largely overlooked older adults. Through a 7-day diary study and debriefing interviews, I examine reasons and factors that influence older adults’ decisions to displace sedentary and screen-based activities. I find that attention demand and overall productivity and quality of activities are key factors that influence older adults’ decisions to engage in displacement. I identify internal and external catalysts for displacement and preferred displacement strategies by older adults in various conditions. These findings emphasize the importance of designing personalized and adaptive interventions to reduce sedentary time, considering the diverse preferences and agency of older adults.enThesisInformation scienceDisplacementIntervention StrategiesOlder AdultsSedentary Behavior