Abstract: We investigate the causal effect of social interaction on individual cognitive functions for elders in China, using the availability of community facilities accommodating social gatherings as an instrumental variable for social interaction, as well as lagged social interaction as an alternative instrument. We find that attending social activities, attending more types of social activities, and attending social activities more frequently tend to improve individual episodic memory and mental intactness. The policy priority is likely on types of activities and participation frequency rather than participation rates. Keywords: Social Interactions, Cognitive Functions, Elder, China JEL Classification Number: J14. I12. O53