Human Emotion and the Uncanny Valley: A GLM, MDS, and Isomap Analysis of Robot Video Ratings Chin-Chang Ho Karl F. MacDorman Z. A. Dwi Pramono Indiana University Indiana University National Neuroscience School of Informatics School of Informatics Institute, Singapore 535 West Michigan St. 535 West Michigan St. 11 Jalan Tan Tock Seng Indianapolis, IN 46202 USA Indianapolis, IN 46202 USA Singapore 308433 kfm@androıdscıence¢com ABSTRACT The eerie feeling attributed to human-looking robots and animated characters may be a key factor in our perceptual 1 2 3 4 5 6 and cognitive discrimination of the human and humanlike. This study applies regression, the generalized linear model (GLM), factor analysis, multidimensional scaling (MDS), and kernel isometric mapping (Isomap) to analyze ratings of 7 8 9 10 11 12 27 emotions of 18 moving ¯gures whose appearance varies along a human likeness continuum. The results indicate (1) Attributions of eerie and creepy better capture our visceral reaction to an uncanny robot than strange. (2) Eerie and 13 14 15 16 17 18 creepy are mainly associated with fear but also shocked, dis- gusted, and nervous. Strange is less strongly associated with Figure 1: Participants rated video clips of 17 robots emotion. (3) Thus, strange may be more cognitive, while of varying human likeness and 1 human by show- eerie and creepy are more perceptual/emotional. (4) Human ing their level of agreement with 27 emotion-related features increase ratings of human likeness. (5) Women are statements and 4 statements related to eeriness, slightly more sensitive to eerie and creepy than men; and creepiness, strangeness, and human likeness. older people may be more willing to attribute human like- ness to a robot despite its eeriness. ment in performing rehabilitation exercises to companion- Categories and Subject Descriptors ship and social mediation [2] [3] [6] [20] [21]. Meanwhile, J.4 [Computer Applications]: Social and Behavioral Sci- android robots are simulating human form, motion qual- ences|psychology; H.1.2 [Information Systems]: User/ ity, and contingent interaction with increasing realism [7] Machine Systems|human information processing [9] [8] [10]. Given the human desire for companionship and for nurturing others [20], which is linked to our biological imperative, it is not hard to foresee the widespread use of General Terms humanlike robots once certain issues are resolved. Human Factors One of these issues is the uncanny valley (bukimi no tani in Japanese). In 1970 Masahiro Mori, a Japanese robotics Keywords pioneer, proposed a hypothetical graph that predicted that the more human a robot looks, the more familiar it is, until Android science, emotion, data visualization, uncanny valley a point is reached at which subtle imperfections make the robot seem eerie [11] [9]. This `dip' appears just before total 1. INTRODUCTION human likeness. Dead bodies are an example Mori gives of In recent years socially-assistive robots have demonstrated something that inhabits the uncanny valley. their ability to help people in everyday life, from encourage- Mori proposed that the eeriness of human-looking robots has to do with self-preservation. In this vein Christian Key- sers has proceeded to explain the uncanny valley from an evolutionary perspective [9]. Drawing on Rozin's theory Permission to make digital or hard copies of all or part of this work for [16], Keysers proposed the phenomenon could be associated personal or classroom use is granted without fee provided that copies are with disgust|an evolved cognitive mechanism for pathogen not made or distributed for profit or commercial advantage and that copies avoidance. The idea is that the more closely another organ- bear this notice and the full citation on the first page. To copy otherwise, to ism is related to us genetically, the higher the probability republish, to post on servers or to redistribute to lists, requires prior specific it will be carrying transmissible bacteria, viruses, and other permission and/or a fee. HRI’08, March 12–15, 2008, Amsterdam, The Netherlands. parasites. Thus, we are most sensitive to signs of disease Copyright 2008 ACM 978-1-60558-017-3/08/03 ...$5.00. in our own species and least sensitive in species that are 169 only distantly related. Others have also proposed a relation ing participant ratings of video clips of robots that vary in between the uncanny valley and evolutionary aesthetics [9]: form and motion quality from mechanical to almost human. given the selective pressures on our ancestors to mix their Although the use of videos precludes the study of contin- genes with the genes of those who could maximize the num- gent interaction, it does enable us to work with participants ber and ¯tness of their progeny, perceptual sensitivity to in Indonesia who had little or no prior exposure to robots. indicators of low fertility or a weak immune system could This was valuable because anecdotal evidence indicates that be responsible for the evolution of mechanisms underlying the eeriness of a human-looking robot habituates with ex- feelings of eeriness toward human forms that are su±ciently posure: People can become accustomed to a robot (or other far from biological ideals. entity) that at ¯rst gave them chills. Studies on the uncanny In a previous experiment, a photograph of an android valley not only bene¯t the ¯eld of human-robot interaction, made disturbing by pulling the eyes back from the face o®ering design principles for building robots to which peo- elicited the subconscious activation of death-related asso- ple can better relate, but also deepen the understanding of ciations [9] (Robot 15 in Fig. 1). In addition, it elicited psy- perceptual mechanisms in cognitive psychology. chological defenses toward those who threatened the par- ticipants' worldview, which manifested in a less favorable 1.1 Research Questions attitude toward foreign students who criticized the partici- RQ1. When observing active robots, what emotion terms pants' home country in the group exposed to the android as are related to attributions of eerie, creepy, and strange? compared with the control group. This experiment suggests RQ2. To what extent are these terms rooted in earlier that an uncanny robot may elicit an innate fear of dying (`perceptual') or later (`cognitive') processing and how does and psychological defenses for coping with the inevitability this involve emotion? of death [4], an idea ¯rst proposed by Sara Kiesler [9]. How- RQ3. Does eerie, creepy, or strange better describe un- ever, as these terror management defenses can operate in canny robots, and how are these terms di®erent? the absence of emotion [18], their relation to eeriness needs RQ4. Do age, sex, and speci¯c features of a robot's ap- to be clari¯ed. pearance a®ect perception? Androids have the potential to trigger other repressed RQ5. What features of a robot's appearance are associ- fears. Having an android Doppelganger may elicit a fear of ated with human likeness? being replaced. Human-looking robots|especially if they could one day rival human intelligence|raise the question 2. METHODS of whether we might not all just be soulless machines. The jerkiness of a robot's movements could lead to a fear of losing 2.1 Participants body control. The cognitive dissonance caused by an entity There were 143 Indonesian participants, 103 male and 40 that lies between familiar categories|electromechanical in female, of whom 35 were 17 to 20 years old (17 being the nature but human in appearance|could also be a factor in age of majority), 85 were 21 to 25, 16 were 26 to 30, 4 the uncanny valley, especially when one of those categories were 31 to 35, and 3 were 36 to 40. The participants were is our own personal and human identity [14]. mainly university students, young professionals, and govern- However, there have not been any empirical studies that ment workers. Compared with industrialized societies like have determined to what extent the eeriness of humanlike Japan, the participants' prior exposure to robots was mini- robots is rooted in emotion and which emotions are impli- mal. Participants were recruited from university clubs and cated in this kind of eeriness. In addition, past studies have Internet cafes in Jatinangor and Bandung, West Java. tended to use still images for stimuli, neglecting the relation between eeriness and motion quality (e.g., jerkiness), timing, 2.2 Materials and Procedures and other aspects of contingent interaction. An experimenter assisted with the computer-conducted There is also some concern about what the appropriate survey. Each participant viewed each of 18 silent video clips dependent variable is in Mori's graph of the uncanny val- presented one at a time in random order (Fig. 1). There ley. The familiarity axis he originally proposed has not been were 17 video clips of robots and one of the woman after widely accepted, perhaps partly because it is di±cult to de- whom one of the robots had been modeled. The 200-by-200 ¯ne negative familiarity, because it implausibly lies beyond pixel clips were displayed on a 14 in. CRT in XVGA mode. total novelty. So the question remains whether strangeness Most of the clips were 6 to 12 seconds in length. They were or eeriness is the most appropriate counterpoint to familiar- played in a continuous loop while the participant answered ity. (Strange is a typical term for describing the unfamiliar.) a survey on the ¯gure featured in that clip. There is no consensus on what emotions are|for exam- The survey consisted of 31 statements and a seven-point ple, psychological kinds, physiological states, dispositions to Likert scale, ranging from strongly disagree to strongly agree. behave, evolutionary adaptations, social constructs, or some For emotion terms, the statements were of the form\The ¯g- combination of these [5].