The study involved subjecting about 80 participants to a spectrum of pain sensations ranging from “mild” to “strong,” while allowing some of them to see Paro and others to touch Paro and then determining whether that mitigated the pain at all.
Our first question for Levy-Tzedek, head of the Cognition, Aging, and Rehabilitation Lab, was how she managed to convince 83 young adults to come into a lab to experience some “strong pain.” It’s possible, or even likely, that the participants were mostly hungry students who would have agreed to pretty much anything, but Levy-Tzedek assured us that “the whole situation was not a stressful or traumatic one.” The pain was generated for just a few seconds by a heating plate attached to the forearm, and the participants had direct control over not just stopping it but enabling an active cooling system to remove the heat as quickly as possible.
“Nobody ran away when they heard the details of the experimental procedure before they signed the informed consent,” Levy-Tzedek told us. “On the contrary—the feedback from participants was positive about their experience, and many of them said (unprompted) that they were willing to return for future experiments.”
Here’s what the experiment looked like:
It’s hard to tell from the impressively stoic participant in the video, but at some point she’s experiencing what the paper refers to as “strong pain,” which is a 6 out of 10 on a scale where 10 is “the most intense pain sensation imaginable.” She also gets some Paro affection, though, and the question is, How much of a difference does that make? In other words, is the pain that she’s feeling while Paro is there significantly less than the pain she’d be feeling if Paro wasn’t there? This sort of thing works if you’re holding hands with a person, so why wouldn’t it while you’re holding a little seal robot’s flipper?
During the experiment, heat-pain intensity was calibrated separately for each individual, and they were asked to rate how intense they felt like the pain was at several points. There was a control group who didn’t get to interact with Paro at all, and everyone else alternated between watching Paro from across the room while the experiment was taking place and “actively touching” Paro. In addition to the recording the subjective pain measurement from each participant, the researchers also took samples of oxytocin (more on that in a bit) and had folks fill out a questionnaire about what they were thinking and feeling.
The primary finding of the study, titled “Touching the social robot PARO reduces pain perception and salivary oxytocin levels,” is that touching Paro does, in fact, reduce the perception of pain. Participants rated their pain sensation as significantly lower when touching Paro robot relative to their baseline pain ratings. The effect was most pronounced in the strong pain condition, when touching Paro was able to reduce the perceived amount of pain from about a 5 (on the 1-10 scale) down to about a 3. When Paro was just there in the room, it didn’t do much of anything for pain, implying that it wasn’t just the robot being distracting that made people feel a little better. Touching Paro also made people happier in general, with an intensity that was correlated with how happy those people thought Paro itself was.
What’s worth highlighting here is the importance of wanted social touch. This same kind of pain reduction effect can be achieved when someone is holding hands with a partner, but not with a stranger, putting Paro in a curious position as a social agent. The researchers suggest that the robot is effective because “touching PARO enabled participants to form an emotional connection with it,” turning the robot into a more effective social agent than a stranger who is an actual human.
The results with the oxytocin were also interesting. Oxytocin is a hormone that the researchers describe as “having a central role in mediating feelings of love, social attachment, and communication,” and it’s been shown that increasing oxytocin and lower perceived pain. The obvious thing to think would be that cuddling Paro increases oxytocin and that’s where the decrease in perceived pain comes from, but when the researchers measured oxytocin levels during the study, they found the opposite: Oxytocin levels decreased in people who got to touch Paro. Levy-Tzedek thinks that this may have been because Paro significantly reduced stress, which also reduces oxytocin, and it turned out that this effect was most pronounced in participants who felt the strongest connection with Paro: “It appears that those who felt they were able to communicate well with the robot (form a social connection with it) benefited more from the interaction, as they experienced a greater reduction in pain (which may be mediated by the reduction in oxytocin).”
This is really the first study to look at Paro in this context, so for more details, we asked Shelly Levy-Tzedek a few more questions via email.
IEEE Spectrum: How important is it that Paro is a robot? Do you think that holding Paro rather than an inanimate stuffed animal is more effective, and if so, why?
Shelly Levy-Tzedek: A previous study with Paro showed that it reduced stress in children more when it was on vs. off. Another study, with a different social robot, showed a reduction in cortisol levels in old adults in the on, and not in the off state. A third study, with Paro, showed greater verbal and visual engagement levels with Paro on vs. off in adults with dementia. In addition, studies from human-human touch interactions show that the touch has to have a positive social meaning for it to be effective in reducing pain. A recent study found that when women held the hand of their romantic partner, they reported a reduction in pain perception, but no such reduction occurred when they held the hand of a stranger. So touch per se does not seem sufficient—it has to be a welcome, meaningful, positive touch, in order to reduce pain perception. We hypothesize that the reason we see such a strong effect of touching Paro is that there was a social connection (however superficial) that was formed with it, and that facilitated the reduction in pain perception. This is supported by the result that high communicators experienced a greater reduction in pain.
Can you suggest some new ways in which Paro could be used to help people, based on your research?
Paro can be used to help manage pain and improve emotional state in young adults (a population that has not been studied in this context: you’ll see that the majority of studies with Paro look at either children or older adults, mostly with dementia). This may be in the context of acute pain—like having one’s blood drawn, or during a hospital stay, or for home use, and potentially also for people with chronic pain, for whom it might help improve the quality of life. These findings are particularly relevant now, during COVID-19, when we are instructed to keep a social distance from other people, including close ones, and there is a reduction in the availability of close affective touch. A social robot may help in this period—not as a permanent solution, but as a temporary one.
It’s hard for most people to get a Paro—what do you think would be the minimum effective robot required to be effective in the same way as Paro?
Of course, I’d have to run studies with other robots to know, but I would argue it is important that it be a social robot, rather than, say—a functional robotic arm used to move objects around, or an industrial robot.
Did all your study participants seem to like Paro? I’ve talked to people* who think Paro is creepy, did any participants see the robot negatively?
We had a large group of participants, so naturally there was a range of responses. The data we report about the pain reduction, and the changes in oxytocin and happiness levels include everyone—those who felt they had a good connection with Paro, and those who did not so much. Following your question, we went back to the numbers and found that one participant rated “did you feel good with Paro?”at 1.95, five participants rated it between 4 to 5, and the other 57 out of the 63 participants rated it above 5 on a scale of 0 to 10 (a common method to measure perception). So the overwhelming majority of participants found the experience with Paro more positive than not.
Are you continuing this research? What are you working on next?
Absolutely—but I can’t tell you about it just yet!
*My partner, for some inexplicable reason, does not love Paro.
Source: IEEE Spectrum