# We Do Not Anthropomorphize a Robot Based Only on Its Cover: Context Matters too!
## 5 Limits
### Intrinsic Limit for Robotic Factors: The Uncanny Valley  
The uncanny valley is based on the following: When an object (here, a robot) reaches a very important degree of anthropomorphism, it triggers a feeling of uneasiness [212; 213]. To highlight this phenomenon, two types of studies are proposed, those that focus on the feeling of strangeness [214; 215; 216] and those that show a preference for machine-like [162; 217] or moderately human-like robots [73]. In human-robot interactions, two elements generate the feeling of strangeness: a humanoid face [214], and/or a similar size and body mass to the interacting person [216]. In consequence, humans can end up trusting and appreciating humanoid robots less than mechanical ones [73; 143; 218]. A meta-analysis (concerning 49 studies based on the Godspeed questionnaire) confirms the preference for robots with low to moderate human resemblance but fails to conclude on the negative effects induced by a strong resemblance to humans [219]. On the other hand, a study of 251 robots shows that a strong human appearance triggers a feeling of strangeness [215].  
The explanation of the uncanny valley phenomenon is based on the expectations induced by the appearance of robots [220]: The discrepancies between human expectations and robot behavior would, thus, be at the origin of this phenomenon [212; 213; 221]. The resemblance would cause individuals to judge the robot according to human normative expectations [222] and, from that point, deviations from the human norm make the robot seem scary [223]. Thus, the extent to which individuals assign to the robot an ability to feel and perceive sensations significantly predicts the feeling of strangeness they report [214]. For this reason, the authors argue that the uncanny valley is a consequence of individuals' attribution of feeling and sensing abilities to robots. Note that the uncanny valley also impacts the quality of moral judgment. Individuals evaluate moral choices made by a human-like robot (iCLOONEY and iROBOT) as less ethical than the same choices made by a human or by a non-human-like robot (ASIMO) [222].  
Repeated interactions decrease feelings of strangeness regardless of the robot (e.g., GEMINOID or ROBOVIE), with both robots being perceived as less strange on the third interaction compared to the first. This indicates that the uncanny valley phenomenon is reduced by increased exposure to the robot [36]. This result seems consistent with the theory presented in [214]. Once individuals know the actual capabilities of the robot, they would rate it as less uncanny and then report more positive feelings. This could explain the beneficial effect of repeated interactions with robots, discussed in Section 4.2.3.  
The uncanny valley phenomenon is present in children [84; 224]. The age of onset is discussed. For some authors, it would appear between 6 and 12 months [225]; 6 m.o. babies prefer to look at a strange avatar rather than a picture of a human; at 12 months, it is the opposite. Other authors suppose it begins between 4 and 8 y.o. [69], from 9 y.o. [226], or even between 8 and 14 y.o. [84]. The explanation for these differences lies in the methodology used, particularly with regard to the variables of interest/measures (fixation time for babies and image classification for children) or the choice of stimuli (robot video or robot image). The variability of the methodology used to measure anthropomorphism and perception of robots thus limits the interpretation of the results.  
Thus, although robot designers seek to maximize the resemblance of robots to humans in order to improve interactions, human-like robots can trigger a feeling of strangeness for the user [215], and can even lead to a reduction of the trust granted to the robot [218]. In conclusion, improving the robotic factors of anthropomorphism alone does not necessarily have beneficial effects on the perception of and attitudes toward robots.