All Are Not Created Equal: The Design and Perception of Humanoid Heads

This paper presents design research conducted as part of Keywords -robot interaction, social robots, a larger project on human-robot interaction. The primary interaction design, design research goal of this study was to come to an initial understanding INTRODUCTION AND MOTIVATION of what features and dimensions of a 's Advances in computer engineering and arti- face most dramatically contribute to people's perception of ficial have led to breakthroughs in robotic technology. Today, autonomous its humanness. To answer this question we analyzed 48 mobile robots can track a person's location, robots and conducted surveys to measure people's provide contextually appropriate informa- tion, and act in response to spoken perception of each robot's humanness. Through our commands. In the future, robots will assist research we found that the presence of certain features, people with a variety of tasks that are phys- ically demanding, unsafe, unpleasant, or the dimensions of the head, and the total number of facial boring. features heavily influence the perception of humanness in Because they are designed for a social robot heads. This paper presents our findings and initial world, robotic assistants must carry out guidelines for the design of humanoid robot heads. functional and social tasks. Much of the research in has focused on improving the state of the current tech- nology. Our goal is to match the technology to the needs of users. Although the tech- i ! i"% nology exists to build a robust robotic i ~!~, • ~, ~. ~iiii~ assistant [26], we lack a principled under- • :'~" ii~~ =~..'i ~-"~...... standing of how to design robots that will accomplish social goals.

...... The goal of our project is to conduct applied research into the cognitive and social design of robots. If robots are going

Figure 1 : Elders interacting with a social robot (Pearl)

Permission to make digital or hard Carl F DiSalvo [email protected] copies of all or part of this work for Francine Gemperle [email protected] personal or classroom use is granted without fee provided that copies are Jodi Forlizzi [email protected] not made or distributed for profit or Sara Kiesler [email protected] commercialadvantage, and that copies bear this notice and the full Human Computer Interaction citation on the first page. To copy Institute and School of Design, otherwise, to republish,to post on Carnegie Mellon University, servers or to redistribute to lists, requires prior specific permission Pittsburgh, Pennsylvania 15213 and/or a fee. USA

DIS2002, London. © Copyright 2002. ACM-1-58113-515-7/02/0006...$5.00

DIS20021 321 to be intelligent social products that assist pragmatic design goal: the design of a new us in our day-to-day needs, then our inter- head for our robot, Pearl. actioh with them should be enjoyable as Pearl was developed as part of the well as efficient. We are interested in issues Nursebot project of product form, behavior, and interaction in (http://www.cs.cmu.edu/~nursebot). Pearl social robots as they relate to accessibility, is used in both laboratory experiments and desirability, and expressiveness. From our field settings as part of our research into research, we will develop models of human-robot interaction. We have re- human-robot interaction that support designed Pearl's head to have modular appropriate and pleasant experiences and features. Modular features will allow us to use these models to create guidelines for easily reconfigure Pearl's head and conduct the design of assistive robots. further experiments on the impact of facial Figure 2: Pearl,our Researchrobot This research is important for the fields of features and dimensions. interaction and product design, human- This initial study was used to inform that re- computer interaction, and robotics. design process. The findings were used to Human-robot interaction is a new area of identify what facial features and dimensions research and the impact of design on this will be most important for us to have field has yet to be understood. control over and direct the industrial design Most of the research efforts in human-robot team in the creation of a new head for interaction have not been focused on Pearl. design [11-13, 27]. Relevant work has been done in related areas such as anthropomor- METHOD phism [9, 20, 22], computers as social Humanoid robot design is in its infancy and actors [22, 23], facial interfaces [19, 28-30], much can be learned from a wide examina- and believable agents [7, 8, 25]. Although tion of . For the sake of Figure 3: ASIMO, an exampleof a Consumer basic and tacit knowledge from other areas this study however, we limited our scope to Product robot of research and design can be brought to existing humanoid robots. We began by inform human-robot interaction, core collecting images of 48 robots from design research is still needed to under- websites, books, and magazines. We stand and articulate challenges of inter- sorted theses images into 3 categories: acting with and designing social robots. Research, Consumer Products, and Fiction. The Research category consisted of robots Many robotics researchers are pursing a that have been created in educational and humanoid robot form as the most appro- industrial research laboratories (n=18). priate form for a social robot [11- 13, 27]. Pearl is an example of a research robot These researchers have assumed implicitly (Figure 2).The Consumer Products category that the head will be the primary place of consisted of robots that have been manu- human-robot interaction. While this factured to be for sale as actual functioning assumption has yet to be scientifically products (n=14). ASlMO is an example of a proven, we have chosen to pursue research Figure 4: The Transformer,an exampleof a Fictional Consumer Product robot (Figure 3). The in the area of humanoid robot heads for a robot Fictional category consisted of robots from television, film, and toys (n=16). The Transformer is an example of a fictional KEY TO PHYSICAL DIMENSIONS robot (Figure 4). A. Width of head Surveys B. Top of head to browline We used the images of the 48 robots to C. Features height construct two paper and pencil surveys. D. Bottom of lip to chin One survey contained an image of the head E. Diameter of eye and body of each robot. The other survey R Pupil distance contained an image of each robot head G. Eye spacing only. In both surveys, participants were H. Mouth width asked to rate each image on a 1 to 5 scale, from Not Very Human Like to Very Human Like. We solicited 20 participants for each Figure 5: Diagramof the comparativephysical measures-- robot posed here is WE-3RIV All robot heads werescaled to 10" height survey. Participants either did the robot

322 I DIS2002 head or the whole robot survey, but not eyelids, and eyebrows, and the total that we surveyed, six did not have any both. number of features present on the head. facial features. SIG is an example of a The heads were scaled to a height of 10 humanoid robot without any facial features The results for each survey were correlated inches so that all of the measurements (Figure 6). However, the presence of facial to assess the validity of robot head scores. would be relative. The images of the face features is very important. The presence of The two surveys were highly correlated, were measured to record the height/width specific facial features account for 62% of suggesting that our scores of the percep-. ratio of each face; the percentage of the the variance in the perception of human- tion of humanness of robot heads are accu- forehead region, feature region, and chin ness in humanoid robot heads. The three rate and valid. region, the size of the eyes, the distance features that increase the perception of between the eyes, and the width of the humanness the most are the nose Robot Head Analysis mouth (Figure 5). (p < .01), the eyelids (p -- .01) and the Using images of the 48 robots we mouth (p < .05) (Figure 7). collected, the heads were coded for the Using the data from the head analysis and presence of eyes, ears, nose, mouth, the robot head survey (we did not include The Dimensions of The Head and the ratings from the whole robot surveys), Features and The Total Number of we constructed two statistical models Features relating to the perception of humanness in The shape of a human head, the dimen- robot heads: The Presence of Features and sions of facial features, and the distribution The Dimensions of The Head and The Total of those features on the head are fairly Number of Features and performed a uniform in , but this is not the case regression analysis on these models to in robots (Figure 8). We saw a similar vari- come to our findings. ance in the width of the head relative to the height. None of the dimensions of the facial FINDINGS features are individually significant in the The Presence of Features perception of humanness in robot heads. One would assume that all humanoid However, the total number of features on robots would have facial features but this is the robot's head is significant in the Figure 6: SIG, a robot without facial features not the case. Of the 48 humanoid robots perception of humanness (p < .01). The more features that a robot head has, the more human-like it will be perceived. The width of the head is also significant in the 100[ 81.25% perception of humanness (p < .03); the 80- wider the head compared with the height, 62.5% the less human-like it is perceived to be. 60- 43.75% Robot Heads In Comparison To 40 - 29.16% Human Heads 20 - 18.75% 16.67% We were curious to know how much the dimensions of a robot's head differed from _Jl the dimension of human heads. We 6[] Eyes Eyelids* Eyebrows Nose* Mouth* Ears combined the dimensions of the facial features of the Mona Lisa, Michelangelo's Figure 7: The presenceand influenceof featureson robot heads * The presenceof these features had a statisticallysignificant effect on the perceptionof humanness statue of David, George Bush, and Britney Spears to develop prototypical human head. We realize that this is not an average Minimum Median Maximum[] head (such as has been constructed by Langlois & Roggman [17-19]). We chose Eye DiameterD 0,25" [] 1.75" [] 4.75" these faces to make a composite from Pupil to PupilO 1.375" [] 4" [] 11.75" because they provide a general represew, a- Mouth Widthr-I 0.875" FI 3,75" [] 9.25" tion of the idealized human face.

Head WidthD 5.25" D 9.63" [] 20" We compared this prototypical human head TopD 8.75%D 35%O 62.5% to a somewhat human-like robot head and a very human-like robot head. For the very MiddleD 28.75%D 60%B 100% human-like robot head we chose the rolt,;t BottomD 6.25%D 11.88%D 27.5% from Metropolis who was ranked the second most human-like of our 48 robots. Figure 8: The dimensionsof featureson robot heads For the somewhat human-like head we Note: All dimensionsare relativeto the head at 10" height

DIS2002 I 323 chose Lazlo, a research robot from MIT, human qualities only through the sugges- pleasant way. Next we need to understand who fell within our median range of human- tion of features. However, designed the aspects of the robot that need to ness and was ranked 19th most human-like features do have a significant effect on the remain robotic enough to clearly display the robot (Figure 9). perception of humanness (p < .01). robot's non-human capabilities and Whether or not the features had been emotional limitations. How Human-Like is Humanoid? designed accounts for 23% of the variance Mashiro Mori developed a theory of The Although all of the robots included in this in the perception of humanness in (Figure 12), which states survey were classified as humanoid, the humanoid robot heads. Kismet (Figure 10) that as a robot increases in humanness majority of them were not rated as being is an example of a robot with highly there is a point where the robot is not very human-like. The mean score on the designed features, DB (Figure 11) is an 100% similar to humans but the balance scale of humanness for the robot heads example of a robot whose features are between humanness and machine-like is was 2.74 (sd 0.68). This does not conflict merely suggested. uncomfortable. Mori provides and example: with their classification as humanoid This finding suggests that in situations 'If you shake an artificial hand [that you robots, for that simply means that their where it is not possible or feasible to perceive to be real] you may not be able to form resembles a human more than it design the actual facial features providing help jumping up with a scream, having resembles any other form. This does, suggestions of those features, in effect received a horrible, cold, spongy, grasp.' however, raise the issue of how human-like affordances for those features, may suffice According to Mori there is a reasonable a robot can be perceived by form alone. in creating an overall perception of human- degree of familiarity that should be Humanness will be defined not only by ness in the robot head. achieved and maintained in humanoid form but interactions through expression, robots [24]. communication, and behavior. IMPLICATIONS FOR DESIGN Between the three categories of Research, The Importance of Design How Human Should a Head Be? Consumer Product, and Fictional robots, As designers we would like to believe that There is a dual challenge in our design Fictional robots are on average the most the design of facial features is important in problem. First, we must understand what human-like and Consumer Products are on the perception of humanness. Not all aspects of robot form lend themselves to average the least human-like. Although the robots have 'designed' facial features. being sufficiently human-like to carry on difference between the categories is not Many humanoid robots express their social interaction in an appropriate and large, it is enough to suggest a trend in

8 8O 7 70 : i~' 6 60 5 50 ~very human-like head []median human-likehead 4 .~ 3

,0 2 1o i 1 B sources of our comparison head 0 0 top features bottom width at 10" height

Figure 9: Contrastof measuresbetween our comparisonhuman head, a very human-likerobot head, and a medianhuman-like robot head

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0% similarity v 100%

Figure 10: Kismet, a robot with designedfacial Figure 11 : DB, a robot whosefacial featuresare Figure 12: Mori'sThe UncannyValley, adapted from features merelysuggested Reichard 1978

3241 DIS2002 Consumer Product robots to appear more engaging the robot; and the need to convey humanness. To project a high level of robotic than human. Whether this trend is an amount of product-ness so that the user humanness in a robot these features should due to the technical constraints of creating will feel comfortable using the robot. be included on the head. a robot for everyday use or reflects the Together, these suggestions create a actual preferences of users has yet to be balance between what we expect of a 5. Skin determined and is an important topic for human, a robot, and a product for an effec- For a robot to appear as a consumer future research. tive design. We have executed these guide- product it must appear finished. As skin, or lines in the design of a new head for our some form of casing is necessary to The relationship of the body to the head robot Pearl (Figure 13). achieve this sense of finish. The head and the importance of the body in the should include a skin or covering of overall perception of humanness is another DESIGN SUGGESTIONS FOR A mechanical substructure and electrical important topic of inquiry. Although this HUMANOID ROBOTIC HEAD components. The skin may be made of soft study focused on the form of the head the or hard materials. body clearly plays a role in the perception 1. Wide head, wide eyes of humanness. To retain a certain amount of robot-ness, by 6. Humanistic form language making the robot look less human, the head We are working toward identifying the The stylized appearance of any product should be slightly wider than it is tall and threshold of humanness that is most appro- form is important in directing our interaction the eye space should be slightly wider than priate for social robots. We know from with it. To support the goal of a humanoid the diameter of the eye. existing literature that the face is extremely robot the head shape should be organic in important in scenarios of human-to-human form with complex curves in the forehead, 2. Features that dominate the face interaction and we know how the human back head and cheek areas. The feature set, from brow line to bottom of face functions in those scenarios [10, 14, mouth, should dominate the face. 30]. However, a robot is not a human and FUTURE RESEARCH Proportionally, less space should be given its form will always be different from that of The effect of interaction on the perception to forehead, hair, jaw or chin. This distribu- a human. A need exists for a set of heuris- of humanness should not be underesti- tion is in contrast to a human's and tics to define the appropriate design of a mated. While this study was conducted combined with the size of the head, will humanoid robot that interacts with humans. with static images of robots isolated from clearly state the form of the head as being any context and devoid of animation or Our research has led us to create a set of robot-like. interaction, our future research will conduct suggestions for the physical design of a similar measures of humanness with physi- new head for Pearl. It is important to note 3. Complexity and detail in the eyes cally present, animated, and contextually that this set of suggestions does not Human eyes are complex and intricate situated robots. We believe that interaction include the design of movement. These objects. To project humanness a robot through speech and movement will greatly design suggestions for a robot head take must have eyes, and the eyes should effect the perception of humanness in into account three considerations: the need include some complexity in surface detail, robots. to retain an amount of robot-ness so that shape of the eye, eyeball, iris, and pupil. the user does not develop false expecta- Our future research will also address robot tions of the robots emotional abilities but 4. Four or more features forms that are not humanoid. We acknowl- realizes its machine capabilities; the need The findings from our study show that the edge that the importance of using a to project an amount of humanness so that presence of a nose, a mouth, and eyelids, humanoid form is still an assumption that the user will feel comfortable socially greatly contribute to the perception of has yet to be proven. We plan to explore other robotic forms and their effect on facil- itating social human-robot interaction. Finally, we plan on examining anthropomor- phic forms and behaviors that exist in prod- ucts other than robots.

CONCLUSION This study showed that the presence of certain features, the dimensions of the head, and the number of facial features greatly influence the perception of human- ness in robot heads. Some robots are much more successful in the portrayal of human- ness than others. This success is due, at least in part, to the design of the robot's head. From these findings we have created Figure 13: Our new reconfigurablerobot head and initial set of guidelines for the design of

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