In this paper, we present a novel dual-robot testbed called DualKeepon for carrying out pairwise comparisons of linguistic features of speech in human–robot interactions. Our solution, using a modified version of the MyKeepon robotic toy developed by Beatbots, is a portable open-source system for researchers to set up experiments quickly, and in an intuitive way. We provide an online tutorial with all required materials to replicate the system. We present two human–robot interaction studies to demonstrate the testbed. The first study investigates the perception of robots using filled pauses. The second study investigates how social roles, realized by different prosodic and lexical speaking profiles, affect trust. Results show that the proposed testbed is a helpful tool for linguistic studies. In addition to the basic setup, advanced users of the system have the ability to connect the system to different robot platforms, i.e., NAO, Pepper.