# We Do Not Anthropomorphize a Robot Based Only on Its Cover: Context Matters too!
## 5 Limits
### General Methodological Limitations
Similarly, studies that do not involve the physical presence of a robot often represent robots as photos rather than videos (e.g., [26; 65; 69; 84; 141; 228]. However, it seems that children appreciate them more when they are presented in video form rather than in pictures [84], as observing the robot's behavior would help them understand its intentions. Thus, data collection through online studies (e.g., [65; 69; 141]) also does not allow for conclusions about in vivo interactions conducted in the real world. Other studies do not necessarily use a robot to study anthropomorphism (for example, avatars and conversational agents, e.g. [9; 12; 37; 44; 46; 110; 179]). Overall, experimental conditions are rarely ecological, as most studies are carried out online or in the laboratory rather than in vivo (e.g., [9; 39; 49; 65; 69; 70; 94; 136; 141; 153; 228]). Studying anthropomorphism without actually placing the participant in a situation of interaction with a robot can distort the results obtained. Furthermore, the duration of interaction with the robots varies considerably across studies: the most common duration is 30 min per session (15-30 min on average, and few studies exceed 60 min) but the longest lasts over 120 min [229]. Overall, interactions with the robot are spread over a short period of time (often a single interaction, the duration of which is not always specified) and few studies are conducted over the long term [229]. We recommend referring to the ABOT database to systematically specify the human-like score of the robots used. The variability of the robot used should also be reduced, so that the results obtained can be generalized. As we have seen in this review, a moderately human-like appearance is preferable, due to the uncanny valley phenomenon. We also recommend privileging in vivo interactions with robots that are physically embodied--and over the long term--in order to approach, as much as possible, the real conditions of human-robot interactions. In addition to the heterogeneity of the studies, there are methodological limitations, which make the generalization of results questionable. A meta-analysis [219] noted that most studies use small sample sizes (the median of the 49 studies included in their meta-analysis was 21 participants) composed of predominantly young participants and students (the median age was 25 y.o.). As a consequence, it is not easy to draw any conclusion about non-student adults, as age affects the way adults perceive robots [94; 158]. The authors also point to the lack of methodological rigor in a substantial number of studies, which omit crucial information about participants (for example, their age or nationality, factors known to influence anthropomorphism). In future studies, it would be appropriate to use a rigorous and standardized methodology. A recent paper advised selecting large sample sizes and reiterating the importance of greater transparency about the detailed characteristics of the sample [219]. This lack of methodological consensus leads to divergent results, which do not allow conclusions to be drawn on certain factors. For example, the effect of the robot's voice on anthropomorphism or the effect of the robot's autonomy on acceptance cannot be determined from the literature. The results are contradictory. Concerning the robot's voice, one study showed no differences in children [37] but a preference for a human voice over a robotic voice in adults [110]. The discrepancy in these results may be due to the age of the participants. Children who anthropomorphize robots more than adults are less likely to perceive the difference than adults. Concerning the robot's autonomy, it is more difficult to interpret the mixed results. Two studies showed no effect of robot autonomy on acceptance [149; 151] and another study showed that robot autonomy had a positive effect on the trust attributed to the robot, but a negative effect on perceived social presence [150]. Is Anthropomorphizing a Robot Even a Good Thing?