Revisiting the uncanny valley theory: Developing and validating an alternative to the Godspeed indices

Mori (1970) proposed a hypothetical graph describing a nonlinear relation between a character’s degree of human likeness and the emotional response of the human perceiver. However, the index construction of these variables could result in their strong correlation, thus preventing rated characters from being plotted accurately. Phase 1 of this study tested the indices of the Godspeed questionnaire as measures of humanlike characters. The results indicate significant and strong correlations among the relevant indices (Bartneck, Kulić, Croft, & Zoghbi, 2009). Phase 2 of this study developed alternative indices with nonsignificant correlations (p > .05) between the proposed y-axis eeriness and x-axis perceived humanness (r = .02). The new humanness and eeriness indices facilitate plotting relations among rated characters of varying human likeness. 2010 Elsevier Ltd. All rights reserved. 1. Plotting emotional responses to humanlike characters Mori (1970) proposed a hypothetical graph describing a nonlinear relation between a character’s degree of human likeness and the emotional response of the human perceiver (Fig. 1). The graph predicts that more human-looking characters will be perceived as more agreeable up to a point at which they become so human people find their nonhuman imperfections unsettling (MacDorman, Green, Ho, & Koch, 2009; MacDorman & Ishiguro, 2006; Mori, 1970). This dip in appraisal marks the start of the uncanny valley (bukimi no tani in Japanese). As characters near complete human likeness, they rise out of the valley, and people once again feel at ease with them. In essence, a character’s imperfections expose a mismatch between the human qualities that are expected and the nonhuman qualities that instead follow, or vice versa. As an example of things that lie in the uncanny valley, Mori (1970) cites corpses, zombies, mannequins coming to life, and lifelike prosthetic hands. Assuming the uncanny valley exists, what dependent variable is appropriate to represent Mori’s graph? Mori referred to the y-axis as shinwakan, a neologism even in Japanese, which has been variously translated as familiarity, rapport, and comfort level. Bartneck, Kanda, Ishiguro, and Hagita (2009) have proposed using likeability to represent shinwakan, and they applied a likeability index to the evaluation of interactions with Ishiguro’s android double, the Geminoid HI-1. Likeability is virtually synonymous with interpersonal warmth (Asch, 1946; Fiske, Cuddy, & Glick, 2007; Rosenberg, Nelson, & Vivekananthan, 1968), which is also strongly correlated with other important measures, such as comfortability, communality, sociability, and positive (vs. negative) affect (Abele & Wojciszke, 2007; MacDorman, Ough, & Ho, 2007; Mehrabian & Russell, 1974; Sproull, Subramani, Kiesler, Walker, & Waters, 1996; Wojciszke, Abele, & Baryla, 2009). Warmth is the primary dimension of human social perception, accounting for 53% of the variance in perceptions of everyday social behaviors (Fiske, Cuddy, Glick, & Xu, 2002; Fiske et al., 2007; Wojciszke, Bazinska, & Jaworski, 1998). Despite the importance of warmth, this concept misses the essence of the uncanny valley. Mori (1970) refers to negative shinwakan as bukimi, which translates as eeriness. However, eeriness is not the negative anchor of warmth. A person can be cold and disagreeable without being eerie—at least not eerie in the way that an artificial human being is eerie. In addition, the set of negative emotions that predict eeriness (e.g., fear, anxiety, and disgust) are more specific than coldness (Ho, MacDorman, & Pramono, 2008). Thus, shinwakan and bukimi appear to constitute distinct dimensions. Although much has been written on potential benchmarks for anthropomorphic robots (for reviews see Kahn et al., 2007; MacDorman & Cowley, 2006; MacDorman & Kahn, 2007), no indices have been developed and empirically validated for measuring shinwakan or related concepts across a range of humanlike stimuli, such as computer-animated human characters and humanoid robots. The Godspeed questionnaire, compiled by Bartneck, Kulić, Croft, and Zoghbi (2009), includes at least two concepts, anthropomorphism and likeability, that could potentially serve as the xand y-axes of Mori’s graph (Bartneck, Kanda, et al., 2009). Although the 0747-5632/$ see front matter 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.chb.2010.05.015 * Corresponding author. Tel.: +1 317 215 7040. E-mail address: kmacdorm@indiana.edu (K.F. MacDorman). URL: http://www.macdorman.com (K.F. MacDorman). Computers in Human Behavior 26 (2010) 1508–1518