There is an increase in the number of functional-service robots in a domestic environment. Although most of functional-service robots are lack expressive faces, research that supports social interaction between users and facial-constrained robots are limited. This study investigated what interaction modalities can be effectively used for naturalistic social interaction between users and facial-constrained robots in a domestic environment. We applied non-facial and non-verbal interaction methods for representing robots’ state. We conducted a 3 (modalities: motion vs. light vs. sound) within-participants experiment (N=25). Using motion was the most familiar way of interaction between a user and a non-facial robot. Also, robots’ perceived sociality was associated with people’s preference for robots. This study shows evidence that robots’ motion would be helpful for users to understand the robots’ mind in a social manner; furthermore, it would enhance users’ acceptance of robots.