ACM Interactions

Authors:
Anna Carter, Ceylan Beşevli, Christopher Dawes, Marianna Obrist

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On one cold spring morning, as I walked down Oxford Street in London on my way to the office, there was so much sensory experience to absorb, such as the chilly tactile sensation of a spring morning and the glaring sunshine. The city was bustling into wakefulness with shops raising their screens. All this contributed to a vibrant sensory experience. After completing speculative futuring technology workshops for public spaces with children, where the students took a keen interest in multisensory technologies, particularly scent, my fascination with multisensory experiences in urban environments was significantly heightened. As I continued along to Euston Road, passing shops and office buildings, the landscape of scents shifted constantly. The aroma of coffee spilled out from coffee shops, while bakeries tempted with the smell of fresh pastries. Even the occasional whiff of garbage bags awaiting collection added to the complex "smellscape" of the city. This simple walk to the office turned into an engaging exploration of experiences that are often taken for granted.

This walk led to the realization that while scent can be easily integrated into private spaces such as homes, what about public spaces like Oxford Street, where design rules are not clearly defined? Moreover, with the advancing digitization of scent, how can current knowledge be applied to virtual spaces, such as virtual reality? Following these ponderings and discussions with our coauthors, we hosted a workshop at the 2023 Designing Interactive Systems conference to explore, reflect on, and discuss the role of scent in a variety of contexts: public versus private versus virtual. We probed the associated considerations on how to deploy and design these sensory experiences in the aforementioned settings, as well as within the field of study [1], while bearing in mind the following principles [2]:

• Multisensory experiences should be used for good and must not harm others.
• Receivers of a multisensory experience must be treated fairly.
• The someone and the sensory elements must be known.

  Insights

→ Developing adaptable scent devices for different environments can promote wider adoption in HCI and interactive systems.
→ Each environment presents unique challenges and opportunities, requiring continued exploration and tailored design approaches.
→ Scent's ability to evoke memories and emotions offers opportunities to deepen connections in areas such as urban design.

While my coauthors and I are all based within the HCI domain, the attendees were from a range of domains, including HCI, in which olfactory research was of interest, such as zoology, psychology, medicine, and child-computer interaction. To facilitate engaging discussions, we curated workshop materials featuring images of scent-based interaction technologies and people in specific contexts. Each domain brought forth unique demands and considerations for scent-based technologies. For example, a scent device can be deployed to encourage behavioral change in lemurs and to evoke memory recollections with dementia patients. The projects did, however, fit into our three environmental contexts: public, private, and virtual. This diversity underscored the expansive scope of scent-based technologies, emphasizing the need for ongoing exploration [3,4]. Our overarching goal was to stimulate dialogue regarding scent's use across these diverse contexts, including best practices and addressing known challenges. In the following sections, we provide an overview of discussions within the three contexts, along with prompts to encourage continued discourse, from design to deployment, on their distinct requirements and opportunities.

Future scentscapes (from left): public (city squares with integrated scent diffusers), private (modern homes with personalized atmospheres), and virtual spaces (immersive extended reality environments with futuristic scents).

Scenting the urban environment: a glimpse into future public spaces, both outdoor (left) and indoor (right).

  Public Spaces

In the context of public spaces, we presented participants with two contexts to prompt consideration surrounding scent. The first context focused on scent deployment within an outdoor city center, where a device deployed sensory experiences to advertise events coming to the city, moving away from traditional public displays. The second context was based on a museum, where scent was deployed indoors to immerse visitors. After reflecting on these examples and their unique demands, we discusssed four avenues to contemplate around the use of scent-based technologies in outdoor public spaces.

Spontaneous interaction. While a variety of scents are naturally occurring within outdoor public spaces (e.g., a walk along Oxford Street), actively deploying scents in public spaces is not that simple [4]. Through this discussion, we evaluated the considerations for allergy reactions, which removes the ability for random and/or spontaneous interaction. This consideration is context specific to outdoor spaces, due to the higher difficulty in receiving informed consent before interaction, especially without a researcher present, which is often the case with outdoor deployments. This highlights the need for more careful consideration of ethical and safety concerns, particularly because smell is a challenging sense to target. Using too little of a scent may not provide enough dispersion for the intended audience, while using the correct quantities or too much may affect everyone in the vicinity, with no easy way to withdraw from the scent. Additionally, it is important to conduct thorough risk assessments to ensure that devices cannot cause harm, especially in outdoor spaces. For instance, in a museum you can inform people and receive consent before they enter. Therefore, our prompts for this contemplation are the following:

• How can we continue this discourse to discover alternate ways to enable research-based sensory interactions in public spaces?
• How can the design of scent-based experiences in outdoor environments be adapted to accommodate different levels of control and customization, balancing the desire for spontaneity with the need for sensitivity to individual preferences and health considerations?

Emotional engagement and nostalgia. A recurring interest for participants was in the emotive abilities presented by scent integration. Scent is such a powerful trigger and can be linked with memories, so when deployed effectively it can evoke nostalgia. While scent's use in galleries and museums has been explored, its intersection with cultural heritage and nostalgia remains largely uncharted territory. It was noted, however, that scent reception and memory association can be very personal. For example, a certain perfume might remind one person of their grandparent but have no memory trigger for another. A diverse range of interactions can happen using a single scent with a range of users. Looking solely at age distribution, younger people will likely have had experiences with far fewer scents than older people, possibly leading to very different interactions. Therefore, our prompts for this contemplation are the following:

• Considering the subjective nature of scent memories, how can the evocation of nostalgia using scent be effectively explored in public spaces?
• How could it be effectively explored within these public spaces for public heritage recollections?

Thought-provoking. Further consideration surrounded the polarity of certain scents and the possibilities for use in public spaces. Compared with other sensory inputs, scent has one of the most significant abilities to alter a person's behavior, memories, and thoughts [5]. One participant referenced Marmite as such a sensory example—some people hate it, while others love it. How could we explore this polarity in response to the concept of scents in a public space? Capitalizing on the strong behavioral responses that scents may evoke (i.e., avoidance or approach), perhaps a strong smell of rubbish could be used to reduce littering. Or scent could be deployed in an area with antisocial behavior rates to reduce these levels. Therefore, our prompts for this contemplation are the following:

• How can the polarity of certain scents be leveraged to influence positive behavioral change in public spaces, such as reducing littering or mitigating antisocial behavior?
• How can we measure this type of interaction?
• How can we responsibly use scent to change behavior?

Transforming scent: innovations for private spaces.

Environmental factors. Deploying technologies outdoors always presents a unique set of challenges, with weather being one of the main considerations (i.e., Can the technology survive rain or wind?). For scent deployments, there is another layer to consider, as weather can also affect the dispersion quality of the devices. For example, if it is very windy, the scent will disperse faster than on a calm day. One participant's work was based in an outdoor zoo enclosure where humidity changed frequently. For devices using powder-based dispersions, humidity would affect their durability and performance. Therefore, our prompts for this contemplation are the following:

• How can we adapt our devices to withstand changing environmental conditions so that the scent dispersion remains consistent?
• What lessons can be learned from other outdoor multisensory technology deployments to inform the development of robust scent-based systems?

  Private Spaces

For private spaces, we used two contexts to prompt participants to think about avenues for consideration. The first context focused on how scent could be used within schools as part of safety training. The second focused on smell health and the use of scent devices within homes for people with mild anosmia (i.e., loss of smell) to improve their ability to detect different scent stimuli. After reflecting on these examples and their unique demands, we discussed two avenues to contemplate for the use of scent-based technologies in outdoor private spaces.

Virtual scentscapes: possibilities for virtual experiences.

Smells for safety. Participants were particularly interested in exploring how educational safety training could integrate scent deployments, such as for boiler or gas leaks. These sessions could then be integrated into the school curriculum along with routine fire drills. One participant suggested a universal safety kit for deployments in schools and homeschooling spaces. Another participant, however, referenced an effort to remove scents in Canadian schools to reduce overstimulation and allergic reactions. Therefore, our prompts for this contemplation are the following:

• How can scent be integrated into educational safety training, including the selection of appropriate scents, dosage levels, and delivery methods to ensure both efficacy and safety?
• What considerations need to be addressed when designing scent-based safety training modules?
• How can these scent safety trainings remain inclusive and accessible to all students, regardless of any sensory sensitivities or allergies they may have?

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Compared with other sensory inputs, scent has one of the most significant abilities to alter a person's behavior, memories, and thoughts.

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Personal scent experiences. An intriguing idea we discussed surrounded the reproduction of personally emotive scents. We spoke about the possibility of syncing scents with memorable or important occasions. People could then use a camera for scents to re-create or print scents when they return home to preserve those memories. They could even re-create scents that had been lost and share them with others within different private spaces, such as homes. As there has been some research exploring odor capture [6], our prompts for this contemplation focus on the broader applications:

• What are the potential ethical implications of re-creating and sharing scents of personal memories?
• What are the potential applications of scent reproduction technology beyond personal memory preservation?

  Virtual Spaces

For virtual spaces, Dimitrios Zampelis demonstrated how augmented reality (AR) and scents could be integrated, with a device that could recognize facial movements and deploy scents based on items the user was looking at within the AR. Based on this demonstration there are two avenues for contemplation.

Portability. One of the key things flagged by participants about working with virtual reality (VR) was its portability and the logistics that would need to be considered when incorporating scent more permanently into VR headsets (e.g., limiting the additional weight of a scent add-on, longevity of capsules, refill capacity, and the additional costs). Although these are necessary considerations, participants felt that integration into virtual spaces could lay the groundwork for building widespread scent-based experiences, as people were more likely to be interested in interacting due to the intrigue of VR in general. Therefore, our prompt for this contemplation is the following:

• How can advances in scent-integrated VR inform integrations into alternate contexts?

Immersion. Incorporating scent into virtual spaces could increase their power of immersion. Participants returned to our discussion on scent and nostalgia, pondering the recreation of lost spaces from childhood and how that could evoke nostalgia and comfort. It is a way to create a virtual version of the concept of go to your happy place. Others were interested in how subtle scent integration could contribute to immersion, akin to the impressionist movement that emphasized subtle light over realistic details in paintings. While incorporation of scent into virtual spaces has been explored, it has mainly focused on enhancing presence within extended reality (XR). There is still much to explore about what scent can bring to XR. Therefore, our prompts for this contemplation are the following:

• Could scent add an ability to create more-intangible ideals of VR?
• Could scent be used to create more-abstract and conceptual VR experiences, by evoking mood or atmosphere with scent rather than representing specific physical spaces or objects?

  Implications for Navigating Scent Interactions

The questions raised by our research interests and curiosity were contextualized further by the researchers working with smell in various spaces and for various purposes through our workshop. Plenty of open questions that demand both technical and user-centered research remain, ranging from unique context-specific concerns to broad questions shared across multiple contexts. We have collated these questions and created the following key action points for future olfactory research in varying contexts.

Context-specific olfactory devices. Enhancing device resilience and building a tool kit with designers and researchers across multiple deployment contexts could significantly enhance the field of scent-based interaction. Being able to adapt and adjust scent devices to perform within a variety of environmental contexts, both indoor and outdoor, could enable the uptake of more olfactory deployments across the HCI community.

Exploring emotions and nostalgia. Using scent to evoke nostalgia within a variety of spaces, either through the re-creation of memories and events displayed in museums or reintegrating and engaging communities with changing public spaces, is an intriguing avenue to explore moving forward.

Scent in education and safety. Safety training for a number of possibly life-threatening hazards is common, especially within education settings such as schools. A promising avenue to explore are hazards with scent-related symptoms or warnings.

Positive behavioral change. Developing methods to measure the impacts and possible knock-on effects of the use of scent deployments to encourage positive behavioral change would be interesting, particularly in exploring how scents can be used to promote behavioral change across a variety of contexts.

Capturing and managing scents. Scent-based interactions are very personal, and there is something deeply interesting about how each person can interact and engage with a scent differently. We believe there is a space for developing techniques to analyze and re-create personalized scents to enable personalized interactions across contexts.

  Conclusion

The potential of context-specific olfactory devices is immense. Collaboration to enhance device resilience and flexibility can drive widespread adoption in HCI. Exploring scent's ability to evoke nostalgia and enhance safety training offers promising avenues. Additionally, leveraging scent for positive behavioral change and personalized interactions presents exciting opportunities for future research and innovation. We discuss context-based requirements and opportunities around smell, spanning from design to deployment. On another note, we invite everyone to pay more attention to the smells as they walk along the streets and see where it takes them.

  References

1. Carter, A.R.L. et al. Scent InContext: Design and development around smell in public and private spaces. Companion Publication of the 2023 ACM Designing Interactive Systems Conference. ACM, New York, 2023, 138–41.

2. Velasco, C., and Obrist, M. Multisensory experiences: A primer. Frontiers in Computer Science 3 (2021).

3. Brooks, J., Lopes, P., Obrist, M., Fernandez J.A., and Kaye, J. Third wave or winter? The past and future of smell in HCI. Extended Abstracts of the 2023 CHI Conference on Human Factors in Computing Systems. ACM, New York, 2023, Article 529, 1–4.

4. Cornelio, P., Vi, C.T., Brianza, G., Maggioni, E., and Obrist, M. Smell and taste-based interactions enabled through advances in digital technology. In Handbook of Human Computer Interaction. J. Vanderdonckt, P. Palanque, and M. Winckler, eds. Springer, Cham., 2023.

5. Brianza, G., Benjamin, J., Cornelio, P., Maggioni, E., and Obrist, M. QuintEssence: A probe study to explore the power of smell on emotions, memories, and body image in daily life. ACM Trans. on Computer-Human Interactions 29, 6 (2022), Article 58, 1–33.

6. Qi, L. et al. Exploring potential scenarios and design implications through a camera-like physical odor capture prototype. Proc. of the 2020 ACM Designing Interactive Systems Conference. ACM, New York, 2020, 2021–33.

  Authors

Anna Carter is an innovation fellow at Northumbria University, specializing in designing technologies for council regeneration. Her work emphasizes accessible digital experiences through participatory design. She currently focuses on building research capacities for early-career researchers and digital civics in outdoor spaces with a sense of place and nostalgia. [email protected]

Ceylan Beşevli is a design research fellow at University College London, focusing on the Smell Care (I-smell) project. Her research explores digital smell training, examining people's motivations and long-term engagement to shape the future of smell care. [email protected]

Christopher Dawes is a research assistant at University College London, investigating multisensory experiences, and a researcher at OW Smell Made Digital, designing digital scent hardware and software. He designs experiments on consumer engagement with textiles, promotes pro-sustainable behavior, and develops sensory technologies, including virtual reality. [email protected]

Marianna Obrist is a professor of multisensory interfaces and deputy director (digital health) at University College London. She cofounded OWidgets LTD, a university spin-off developing novel digital smell technology. Her research, which is shaping the field of multisensory HCI, is focused on touch, taste, and smell experiences. [email protected]

 

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