PiRat: An autonomous framework for studying social behaviour in rats and robots Robotics lab: Scott Heath 1 , Carlos Andres Ramirez-Brinez 1 , Joshua Arnold 1 , Ola Olsson 1 , Jonathon Taufatofua 1 , Pauline Pounds 1 , Janet Wiles 1 Rat lab: Eric Leonardis 2 , Emanuel Gygi 2 , Estelita Leija 2 , Laleh K. Quinn 2 , Andrea A. Chiba 2 Abstract— The use of robots, as a social stimulus, provides several advantages over using another animal. In particular, for rat-robot studies, robots can produce social behaviour that is reproducible across trials. In the current work, we outline a framework for rat-robot interaction studies, that consists of a novel rat-sized robot (PiRat), models of robotic behavior, and a position tracking system for both robot and rat. We present the design of the framework, including constraints on autonomy, latency, and control. We pilot tested our framework by individually running the robot rat with eight different rats, first through a habituation stage, and then with PiRat performing two different types of behaviour — avoiding and frequently approaching. We evaluate the performance of the framework on latency and autonomy, and on the ability to influence the behaviour of individual rats. We find that the framework performs well on its constraints, engages some of the rats (according to the number of meetings), and features a control scheme that produces reproducible behaviour in rats. These features represent a first demonstration of a closed-loop rat-robot framework. I. INTRODUCTION There is an increasing use of robots in social interaction studies on rats (e.g., [1], [2]) as well as on other animals (e.g., fish [3], penguins [4]) [5]. Evoking and measuring neural and behavioural responses to a carefully controlled social stimulus is a powerful tool for studying and understanding the rodent brain. There are several advantages to using embodied robots in these contexts: i) running online models of behaviour, enables the implementation of what may be perceived as a social “other” while their behaviours can be well described over time, ii) interaction with well-described robotic partners can act as an important comparison case for the interaction between two mammals, iii) a social robot allows for the experimental manipulation of physical and sensory properties/characteristics, to assess the possible critical features that drive social behaviour, and iv) robots allow experimenters to create reproducible behaviours or adaptive models, allowing invesitgation of the importance of adaptability and responsiveness for social interaction. When creating a robot as a social stimulus for a rat, it is not feasible to implement the entire neural architecture of a rat; so part of the challenge is identifying which social This work was funded by [NSF BRAIN EAGER 1451221; NIMH R01 5R01MH110514-02; AOARD FA2386-16-1-4026] 1 Engineers are with the School of ITEE at the University of Queensland, St Lucia, Queensland, Australia scott.heath@uq.edu.au 2 Neuroscientists are with the Department of Cognitive Science, Univer- sity of California, San Diego, La Jolla, San Diego, CA Fig. 1. A rat interacts with a stationary PiRat. Rats were willing to approach and inspect PiRat. PiRat’s whiskers are new sensors that are currently under development, but are not used in the current study. features are important for a robot to implement and exhibit to the rat. Previous studies have approached this using wizard- of-oz (WoZ) control of the robot [1], or using autonomous robots [2]. The benefit of using a WoZ style of control is that the experimenter can create the behaviour for the robot using all of the sensory and cognitive apparatus of the human. However, WoZ requires expertise and different experimenters will not be able to reproduce exactly the same behaviour. The benefits of autonomy are that the control of a robot is consistent with their algorithms. The difficulties with autonomy are in the implementation: sensing and representing the environment with enough detail to be able to act socially. In practice, all studies with autonomous agents have some degree of human involvement. The aim of the PiRat project is to develop and iteratively improve a set of rat-sized robots and related software and hardware in order to study rat social interactions. The key challenge in achieving this goal is creating the capacity for the robot to adapt to the rat’s behaviour. The ability to adapt behaviour to the individual differences, encountered in the social world, is essential for successful social interactions. In this paper, we describe the development and evaluation of a rat-sized robot and tracking framework for closed- loop, rat-robot interaction studies. The components of this system are described in detail. The design of a new robot platform is described, along with a new tracking system that is capable of determining the location and orientation of the 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) Madrid, Spain, October 1-5, 2018 978-1-5386-8094-0/18/$31.00 ©2018 IEEE 7601