4. Eye-Tracking and Survey Results
The face and the body attracted most of the overall attention. In particular, the face was the most watched feature regardless of the age group. Moreover, eye-tracking results revealed that the participants’ gaze behavior significantly differed by age group (Table 2
), which partially supports H1
. Older adults looked at the areas around the eyes and the noses very often with little attention paid to the rest of the AOIs. They focused significantly more times and for a longer duration on the face (p
< 0.01) but significantly less on most of the other AOIs than younger adults. There were no statistically significant differences in some AOIs, but such data were consistent with the overall trend and did not limit the interpretation of the results.
Older adults’ high interest in the bear’s face is also supported by the heatmap images in Figure 4
. They gazed at the eyes and the noses very often. Indeed, 20 out of 31 older adults never looked at other AOIs but only focused on the face. This is evidenced by the eye-tracking data of the older adults on arms and legs. They focused little attention on the right arm and the left leg (Table 2
, Figure 4
Younger adults also looked at the face for the longest of the entire body, but they looked at the other AOIs more compared to older adults (Figure 5
and Figure 6
, and Table 2
). Only two of the younger adults focused only on the face (P12 and P14). Table 2
shows that younger adults focused on AOIs other than the face significantly more than the older adults. After the face, the torso drew the most attention. The convex abdomen, the small red colored logo, or the black parting lines may have affected the results, which is further explained in a later section.
The gaze plots also show that the robot’s face drew much attention. Moreover, it was the most popular starting point for the gazing at the robot. Twenty-nine older adults fixated on the face first, while two started by looking at the torso (P17 and P19). The majority of the older participants focused only on the bear’s facial features (n = 20) for the duration of the experiment. Others looked at the other body parts briefly (n = 11). Seven of them viewed the face first and then moved their gaze down to the abdomen; P5 and P13 gazed at the face first and then the ears, while P17 and P19 stared at the bear’s torso first and then at the face (e.g., Figure 7
Most younger adults also focused on the face first (n = 22, Figure 8
). Then, their focus moved to torso (n = 9), ears (n = 9), or arms (n = 2), or it remained on the face (n = 2). We also observed that, for some younger participants, torso (n = 4), ears (n = 3), arms (n = 1), or legs (n =1) were the starting points of gazing at the robot.
In summary, the eye-tracking data revealed that the bear’s face attracted the most attention, followed by the torso. Older adults showed higher interest in the face than younger adults. They also gazed at fewer of the other AOIs than younger adults.
Survey results showed that the robot was significantly more preferred by older adults (Table 3
), which supports H2
. Its physical attractiveness and social likeability were rated as significantly higher by the older adults (Table 3
), which supports H3
. The rationale behind the preferences for the robot is discussed in a later section.
5. Interview Results
We conducted interviews to investigate the participants’ gaze at the robot and examine their impressions in detail. We highlight the age-related differences in their viewpoint of companion-robot design. We report each group’s opinions, focusing on the AOIs that participants primarily gazed at.
5.1. Overall Impressions
The impressions of the older adults were quite simple: they loved the bear very much and were fascinated by its design. Moreover, they focused considerably on the bear’s face. The reason they gazed at the face the most was simple as well. Similar to when people look at other people [68
], the eyes of the older adults were instinctively fixated on the robot’s face:
“The first thing I noticed was the bear’s face. Just like when you talk to people, you see them face to face.”—P25, older.
“When you see another person, you first look at their eyes. I think it’s just a habit to have eye contact.”—P13, older.
“Because people see each other’s face and eyes when they first meet, the face naturally comes in the sight first. You can’t just look at their legs first, because that’s not what they’re used to.”—P11, older.
Then, they recognized the robot as a bear and felt that it looked very similar to a typical teddy bear. Nobody mentioned that the robot’s appearance was unusual.
“I recognized the robot as a bear at a first sight. Overall, I think the quality of it is high. It almost looks like a finished product. The balance between the top and bottom parts is good and I personally can’t seem to find a flaw.”—P5, older.
“At the first glance, its shape, a bit like a teddy bear, caught my eye. I know why it caught my eye. Because we are familiar with teddy bears in general, and its overall impression was just like a teddy bear. Eyes, then ears, and then this round face. From these features, I had an instant feeling that this was a teddy bear.”—P4, older.
Younger adults were also positive toward the robot and stared at its face for quite a long time. However, they tended to look at the robot’s appearance in more detail compared to the older adults. As a result, the older and the younger adults’ viewpoints of the robot differed. Unlike the older adults, the younger adults described many potential improvements of the robot. One example is that approximately one-fifth of the younger adults (n = 6) reported that the robot did not look like a typical bear or teddy bear. In particular, its thin arms and thick legs were one of the causes of that opinion:
“I didn’t think it was a bear, maybe because it’s face was too wide? And its body is nothing like what I know of a teddy bear. I think that’s because its arms are thin, and legs are bulky.”—P14, younger.
“On the whole, it is felt a little different from the other bears I’ve been familiar with. The face is too long in its width and the arms and legs also look different. And for legs, you see, one of the main features of a bear is its paws. But there are no such parts with this robot, and I have a kind of wonder whether this is really a bear.”—P25, younger.
Younger adults criticized that its head was large (n = 5) and wide (n = 4) compared to other body parts, and they felt it looked awkward and unnatural. Some of them added that the face seemed a little bit heavy (n = 3).
“When I first saw it, I thought it was cute because its eyes, nose, and mouth reminded me of a teddy bear. But then, later, I thought it was a little weird. (laugh) The face is too big and its facial features are cute yet a little weird.”—P6, younger.
“The face is too.. wide. Haha. I… um, I don’t think it’s good.”—P9, younger.
On the other hand, most of the older adults viewed its head positively. They were satisfied with the rounded face and ears, which reminded them of teddy bears. There was also an opinion that a large face would be advantageous for older people with low vision to easily see the screen (P24). Only a few of them reported that it was too large (n = 5). Two of them suggested that increasing the size of other body parts (P1) or reducing the size of the head (P20) would lead to a more balanced design: “I think it’s better to downsize its head to get more balance. I think right now, the upper part is too big.” — P20, older. Three older participants did not mention the need for modification (P9, P11, P12). P9 felt its face was large, but it still felt cute to her: “I have a feeling that its face is somewhat large. Having said that, the robot has a cute appearance overall and I only mentioned its large size in case I have to come up with any of its disadvantages. For me, I like the way its eyes appear large from its face, and the large eyes themselves gave me the impression of openness, which was nice.” — P9, older. In summary, several older adults recognized that the robot’s head was a little large, but they did not consider it a negative aspect of the design.
Older adults believed that the bear had a friendly design. They suggested that the robot’s rounded look, particularly its rounded abdomen, made it seem more friendly.
“It is round with no sharp edges, which makes it quite friendly and cute. In general, there are no sharp edges, and its belly, ears, eyes, and face are all round, which makes the bear look friendly and soft. I think the belly poking out is so cute.”—P23, older.
“The belly pokes out, so it looks cute. You know, it reminds me of those mischievous plush toys kids play with. Their bellies are sticking out like this. Or those other toys that look at you like this, showing their belly button. I think it is designed well.”—P24, older.
The older participants considered the rounded shape (n = 11) and torso (n = 5) of the robot so charming that it formed functional expectations of the robot’s capability in some of them [18
], which was addressed only in the older adult’s interviews. Although we did not ask any questions about its perceived role, some of them mentioned that they could talk with the bear (P4, P7, P8) [13
]. Others even mentioned that they felt like it could be their friend (P31, P34) [13
]. These positive impressions developed into a strong preference for the robot (Table 3
“It’s so cute. It looks like it’s going to talk to me like a little child. Oh, I like that feeling. I think everything about this is cute. I can’t think of anything wrong with it. I feel I can have easy conversations with it like I’m talking to a friend.”—P7, older.
“Overall, it looks cute and funny. I feel it’s going to do something fun with me and talk to me. I feel it’s going to give me a lot of joy.”—P8, older.
“It seems to be bright and affable. I feel it is very friendly just like a puppy, like a pet dog.I feel I should protect this robot and it will be my friend. I think it will run errands for me.”—P34, older.
The abdomen was also recognized as a friendly feature by younger adults (n = 7). Since it reminded them of the bear dolls or a character (e.g., Winnie-the-Pooh), it reduced the machine-like characteristics of the robot. They were familiar with the abdomen, and that was the reason they focused on it.
“Pokey bellies are cute. Winnie-the-Pooh or other plush toys usually have big bellies. I think that’s because people like it. I think that’s why I first looked at its belly. This one feels more friendly, even though it’s a machine, because it has a pokey belly.”—P5, younger.
“Its belly is poking out, so it didn’t occur to me that it would be offensive. In contrast, it felt so friendly, the pokey belly. Like Winnie-the-Pooh. This robot has a similar body shape to littletoddlers.”—P31, younger.
As shown in Figure 5
and Figure 8
, the parting lines and the logo attracted some younger adults’ attention to the torso and other AOIs around it. Perhaps the noticeable colors may have drawn their attention, but those factors had little impact on their impression of the robot. Only a few short comments were made about the parting lines (n = 3) and the logos (n = 2) during the interview. Due to the parting lines, P2 envisioned the modular design and said the robot seemed to be easy to repair. P20 and P23 instinctively stared at the logo to read what is written. Only P30 rated the lines negatively as unnecessary and visually distracting.
5.4. Arms and Legs
The arms and the legs did not attract much attention from the older adults. Only a few older participants (n = 5) were interested in them. Their feedback was less specific than that of the younger adults, and most of them were focused on the arms rather than the legs. Although the bear did not show any movement, they viewed the toy-like small arms favorably and felt like holding them:
“When I first saw this bear, I thought to myself, I could just hold both of its hands! I felt that I would just hold its hands, if given some kind of assurance that I may hold them.”—P2, older.
Other older adults mentioned that the arms are a little thin (or short) compared to the legs. They thought it would seem more stable and balanced if the arms were a little thicker (n = 5): “I think this arm is a bit thin... You see, its feet are as thick as this. If the arms are about twice as thick as they are now, it will look more stable, in better shape overall.” — P18, older.
Some younger adults’ responses were similar to those of older adults. They also preferred the robot’s arms over its legs (n = 7). To them, it seemed like a doll that wanted to hug them (P31, P33).
“The arms were sticking out, just like how other teddy bear plush toys look and beg for your hug. It was cute, so I think that’s why I kept looking at its arms.”—P33, younger.
However, detailed gaze patterns of younger adults were linked to negative responses on the arms and the legs. More than a third of them pointed out the limbs and criticized the exaggerated size of the limbs (n = 11), stating that it makes the robot seem unnatural and imbalanced. The disproportional limbs also made the robot feel distant from their preconceptions of a bear. Still, a few of them thought it was cute (P17, P24, P29):
“The legs looked quite puffy, which makes it unbalanced throughout its arms, belly, and legs. The legs are as large as human. So, I thought it was a little odd, and asked myself whether teddy bears usually look like this. I think the shape is quite.. different from what people generally think of teddy bears. On the positive side, its ugliness makes it cute.”—P29, younger.
“The arms.. do not look like bear’s. They’re too thin.”—P22, younger.
“Right now, it is more like a robot so I think it will be better if it looked a little more natural. This may be difficult because of some parts, but I think it would have looked better with bigger arms.”—P10, younger.
More than half of the older adults (n = 17) responded that the current size of the bear is suitable for communication. The prevalent opinion among them was that they would be scared if the robot increased in size: “I feel like the bear is going to follow me wherever I go just like a puppy. With such a feeling, it comes across as a friendly companion. But if its size is too big, I might feel a bit overwhelmed by it. So I think the size is fine as it is. If it is too large, I might be intimidated by it, thinking it could be something… beyond my control.”— P12, older.
On the other hand, some older adults viewed the current one as too big (n = 7). They thought that the smaller the companion robot is, the more adorable it would be, since it would look like a baby: “When it’s too big, it’s not cute. The reason why babies are cute is they are small. We all know human babies are so cute, and that’s because they’re so tiny.”
— P11, older. They argued that they would easily talk with the robot, even if it decreased in size. P27 envisioned that the companion robot would be helpful for people living alone. Considering the dimensions of their living space, she guessed that a smaller-sized robot would be suitable for them. P11 and P30 held the same view that the current one would be difficult to place at home due to its size [70
“I think people who live alone would like this bear better. People who live alone usually don’t live in a big house. Since they live in small places, I think it’ll be irrelevant if it’s even smaller than this bear.”—P27, older.
Some older adults insisted that the size of the robot should be slightly larger than the current size (n = 7). They thought the larger one would be more noticeable at home and it would be more convenient to angle toward the robot (P9, P29). P9 guessed that taller robots would be advantageous when talking with them from a distance.
“I think it’ll have to be a little bigger than the current size. I think this is too small. You need to have an even eye level to be able to have conversations. With this size, people will have to bend their back, which makes it uncomfortable. Even if people talk to this bear from a distance, they still need a taller robot.”—P9, older.
“Perhaps a little larger than this one. The robot would look out of place if it were too big. If it is in the house, it needs to be seen easily. In that sense, it should be a little bigger than now.”—P15, older.
“When I stand up, this robot is on the floor, so I can’t see the screen well. Things like the texts on the screen get farther away in those cases, so I think it might be better if its height were a little taller.”—P18, older.
The opinions of the younger adults were evenly divided into three groups. Ten respondents said the current size of the bear was suitable, ten participants wanted a larger one, and eleven participants preferred a smaller one. Among the three groups, those who criticized its head size demanded the robot be minimized. They hoped to scale its head down and height simultaneously. P24 explained why the bear needed to be smaller - the large head made it look heavy, unstable, and it felt like it would be easily broken if it fell [15
]. In agreement with the viewpoint of several older adults, some younger adults thought the small size of the robot would not affect communication, rather it would make the robot seem more friendly.
However, younger adults who preferred a taller robot (n = 10) did not express any opinions about the size of its head. They argued that if the robot navigates at home autonomously, it should be taller to reach eye level. The current size would be so small that they would have to bend at their waist to see the screen, which was also pointed out by the older adults. Some younger adults were concerned that if the robot is too small, it would be regarded as a toy or a simple machine, not a companion (P13, P31). In summary, both groups concluded that the robot needs to reach their eye level.
In this study, we aimed to investigate the age-related differences in attending the design of companion robots. Unlike most of the previous robot design studies that used surveys or interviews [6
], we used eye-tracking methodology as well. Although surveys and interviews are efficient in collecting data, they may be affected by several types of biases (e.g., response bias) [71
]. Beyond self-reported data, recent studies have adopted eye trackers to evaluate product designs [12
]. They reported that eye-tracking methodology can objectively investigate the cognitive responses of users [24
]. However, the limitation of eye-tracking methodology was also discussed in a previous study [30
], i.e., the visually most attractive design is not necessarily the most preferred design. Some researchers suggested that eye-tracking studies should be complemented by a survey [24
]. Therefore, our study conducted surveys and interviews to complement the eye tracking methodology and understand the impression of the robot design.
It is widely known that, when people look at other people, they look at their faces [68
]; the same is true for humanoid robots [12
]. Our findings show that the bear’s head drew the most attention, and it was the first area that the participants fixated on. These findings are consistent with [12
], which reported that participants gazed at the head the most among the nine AOIs of the humanoid. In addition, the researchers reported that eyes and nose of the humanoid attracted the most of the fixations, which is similar to the gaze behavior people exhibit when looking at other people; they focus on the primary facial features, e.g., eyes and nose [33
]. Such gaze behavior was also observed in our study (e.g., Figure 4
and Figure 7
), which supports the claim that this type of gaze behavior is applied to zoomorphic robots.
In this study, younger adults’ detailed gaze behavior seemed to be linked to low preference for the bear. This result is similar to the findings of [15
], which reported the negative attitudes of younger adults toward animal-like companion robots. For instance, the younger adults in [15
] viewed the bear as unstable and susceptible to breaking in case of a fall. They also disapproved of other animal-like robot designs. Conversely, older adults viewed the bear as stable and familiar [15
]. Some of them disapproved of the rabbit-like design concept, but they all approved of the ears of the rabbit, which were criticized as “useless” by the younger adults. In summary, these results indicate that the preferred design and important design features could vary for different age groups.
The bear’s appearance allowed the older participants to attribute positive traits to it. Its rounded shape and abdomen appealed to them. As a result, some older adults came to expect that the robot could perform useful tasks for them (e.g., have a conversation and run an errand) [18
], which corresponds with some social likeability questionnaire items from [13
]. Some older participants thought this robot might “be a friend of” them [13
], and others mentioned that they wanted to have a conversation with it. Moreover, their expectation seems to be linked with “attractiveness halo” [74
], which is the psychological tendency of attributing more positive traits to attractive people. As Norman claimed in his book, the rounded shape and the attractive appearance [75
] produce positive affects toward the robot, which may be extended to judge the robot as likely to talk and interact with them kindly [19
Furthermore, baby- or animal-like physical features of the bear might have elicited positive responses from the older adults as argued by Lorenz [76
]. Lorenz proposed the concept of a baby schema: a set of cute physical features common to human or animal (e.g., large head, round face, and protruding cheeks) motivates positive social responses, such as nurturance and affection. Hinde and Barden also argued that people respond positively to baby schema features in adults, animals, and human artefacts [77
]. In line with these concepts, Breazeal and Forest suggested that cute appearance of a robot could encourage people to react emotionally to the robot [78
]. Therefore, the bear’s appearance may have attracted older adults and motivated them to interact with it.
On the other hand, the younger adults did not report such functional expectations of the bear. They were more negative than older adults about the size of its head and exaggerated arms and legs. Their impressions of the bear design were also somewhat different from those of the older adults. In this regard, the bear might have failed to shape such expectations in the younger adults, which supports that there might be age-related differences in recognizing the robot’s appearance.
This study utilized eye-tracking glasses and a mockup for participants to consider the size of the robot when evaluating its physical likeability. This is because design evaluation with two-dimensional images on the monitor is “often too limited” [63
] compared to the use of three-dimensional mockup. Further, people usually look at the robot from various points of view. Although the way we utilized wearable eye trackers was different from the typical method of using them—investigating the gaze behavior of participants during movement [24
]—our method was effective in eliciting the participants’ opinion on the robot’s size. The majority of the participants thought the current size of the bear was suitable, and they noted that it might be scary if it became larger than its current size. These opinions are similar with the report from [6
]. In that study of robot appearance, most of the elderly participants first insisted on the robot’s size from the interviews; they preferred small-sized robots such as Nao (573 mm in height) rather than human-sized robots [6
]. Older participants in another study [70
] also expressed similar opinions. They expected the robot to be smaller than them and thought that it would fit better in their homes than a larger one. These findings show that the size of the robot is an important element of robot’s design, and older adults tend to prefer small-sized robots [6
The empirical findings of this study provide several implications for companion robot designers; the preference of prominent physical features and design varies by age. Older adults mostly focused on the companion robot’s face, which is the most important feature for them. In addition, the rounded look and the animal-like or animation character-like appearance may be helpful in forming positive impressions at an early stage. Finally, the size of the robot determines its accessibility. More than half of the older adults favored the current size of the robot, but others hoped to change its height. They also commented that the size of the robot should be determined depending on the robot’s mobility or dimensions of its living space [70
This study has several limitations. First, the findings are limited to the bear-type robot used in this study. The age-related differences in some AOIs might be attributed to the distinctive design features of this bear-like robot (e.g., large head and convex torso), and the differences may not be consistent if using other animal-like robots. Therefore, further research on different designs and sizes of robots is required.
Second, the results of this study are limited to the participants’ first impressions of the robot design. Their views, investigated through a short eye tracking interaction and brief interview, could be changed by the robot’s interaction capability or long-term usage [80
]. Therefore, future studies should investigate if interaction time affects participants’ fixation patterns and impressions of the companion robot design (e.g., [8
Third, other variables may have influenced the differences in the fixation patterns. In this study, some AOIs received little attention from the older adults, which might be attributed to their cognitive decline. Due to aging, their reaction time and processing speed decrease [40
], thus the older adults may have looked at each AOI more slowly than the younger adults [41
]. For instance, the average fixation duration of the older group on the bear’s face was slightly longer than that of the younger group (Table 2
). The older group also focused on the face significantly more times. Although the average fixation duration on the bear’s face was not significantly different, several previous studies reported that older adults require longer fixation to perceive visual information than younger adults [82
]. Additionally, they may not have had enough time to look at the other AOIs. If we had collected and analyzed the data for more extended periods of time as in [12
], the results might have been different. In this regard, the older adults’ fixation pattern may not be related with their impressions of the robot design. Further research should consider more variables to investigate the relationship between fixation patterns and attitudes toward the robot design.
Fourth, this study was conducted with a small number of participants, and our data may not have enough statistical power to investigate the age-related differences in recognizing the design of companion robot. The effect sizes of most AOIs were medium or large [84
], but some of them were small (e.g., left arm) or could not be calculated (e.g., right arm and left leg). The effect sizes of some AOIs were small because the participants paid little attention to them. These results indicate that future research should be conducted with longer period of interaction and larger sample sizes.
In addition, future studies should investigate more types of older adults. The older participants in this study were 62.3 years old on average, which is “relatively young” [86
], but the impressions of other older adults may vary by age. For instance, older adults aged over 85 and those aged less than 85 had significantly different preferences of companion robot design [16
]. Additionally, their impressions might be different depending on their physical or mental health [16
Moreover, we found several significant differences in the eye-tracking statistics, but in this study, the number of older female adults was more than twice that of the older male adults. Therefore, the data of the older group may have been biased toward the eye-movement behavior of older female participants. When we performed Mann–Whitney U test for older participants by gender, we found no significant differences for AOIs other than the face. The older male adults’ total fixation duration on the face (M = 8.050) was significantly longer (U = 39, p = 0.033) than that of the older female adults (M = 6.543), and the older male adults’ average fixation duration on the face (M = 0.431) was also significantly longer (U = 39, p = 0.033) than that of the older female adults (M = 0.318). This shows that older male adults focused considerably on the face, but the small number of the older male adults limits the further interpretation of this result. In addition, we performed Mann–Whitney U tests for all participants, but there were no significant differences by gender except for the right arm and the left leg. No significant differences were found between the younger male adults and the younger female adults either. Therefore, further research on the impacts of gender should be conducted in the future.
Furthermore, the older participants’ high preference of the bear might be also attributed to the large proportion of females in the older group (Table 1
). Although the Mann–Whitney U test found no significance for the bear design preference by gender (U
= 55, p
= 0.147), the bear tended to be more preferred by the older female adults (M
= 4.583) than the older male adults (M
= 4.286). The survey results of the BEHAVE questionnaire were also consistent with the results of the design preference. The Mann–Whitney U test showed that older female adults (M
= 21.875) evaluated the social attractiveness of the robot as higher (U
= 33.5, p
= 0.016) than older male adults (M
= 19.286). We found no significant difference for physical attractiveness (U
= 74.5, p
= 0.647), but it was evaluated as higher by older female adults (M
= 17.083) than by older male adults (M
= 16.571). Therefore, with a larger sample size and different statistical analyses, the effects of gender and other factors could be investigated in future work.
Finally, the quality of the collected gaze data might have been influenced by eye tracker slippage. Due to the nature of the head-worn eye tracker, the movement of the facial muscles might have affected the data quality [46