Take a deep breath; what do you smell? While sight and hearing dominate our perceptions, the sense of smell is often overlooked, even undervalued. However, the importance of our sense of smell goes beyond detecting odours. It shapes our emotions, memories, behaviour, and quality of life. Recent advances in olfactory interfaces have sparked discussions about the future of smell in human-computer interaction. While efforts mainly focus on the realization of new olfactory interfaces, here we collectively explore alternative worlds centred around the sense of smell. First, we conducted a design futuring workshop involving individuals with varying smell capabilities and expertise to envision and discuss smell-centred futures. Then, through iterative reflection, we arrived at three smell worlds presented as narratives and visuals. From this conceptual work, we offer new perspectives and generative possibilities for design research that prioritizes our noses.

Human perception of touch is a complex interplay of sensory inputs, extending beyond tactile stimuli to include visual and auditory cues. Yet, the potential of olfactory cues (e.g., scents) to enrich our understanding and experiences of digital touch remains largely unexplored. This paper explores the integration of scent with digital haptic feedback, specifically focusing on the perception of textiles using an ultrasonic mid-air haptic device. In an initial validation study, we identified scents associated with the tactile properties of roughness, smoothness, coldness, and warmth based on participant ratings (n = 31). In a subsequent immersive Virtual Reality (VR) experiment, we explored how these scents might affect perceptions of digital textiles presented using ultrasonic mid-air haptics (n = 32). Our results suggested that while scents did not affect the tactile properties of digital textiles, participants reported the sensations feeling more realistic and more arousing according to the scent delivered. This multimodal integration of scent with digital haptic stimuli can open up the creation of more immersive experiences and more in-depth understanding of digital material properties.

Previous research has shown the influence of smell on emotions, memories, and body image. However, most of this work has taken place in laboratory settings and little is known about the influence of smell in real-world environments. In this article, we present novel insights gained from a field study investigating the emotional effect of smell on memories and body image. Taking inspiration from the cultural design probes approach, we designed QuintEssence, a probe package that includes three scents and materials to complete three tasks over a period of four weeks. Here, we describe the design of QuintEssence and the main findings based on the outcomes of the three tasks and a final individual interview. The findings show similar results between participants based on the scent. For example, with cinnamon, participants experienced feelings of warmth, coziness, happiness, and relaxation; they recalled blurred memories of past moments about themselves and reported a general feeling of being calm and peaceful towards their bodies. Our findings open up new design spaces for multisensory experiences and inspire future qualitative explorations beyond laboratory boundaries.

Driving is a task that is often affected by emotions. The effect of emotions on driving has been extensively studied. Anger is an emotion that dominates in such investigations. Despite the knowledge on strong links between scents and emotions, few studies have explored the effect of olfactory stimulation in a context of driving. Such an outcome provides HCI practitioners very little knowledge on how to design for emotions using olfactory stimulation in the car. We carried out three studies to select scents of different valence and arousal levels (i.e. rose, peppermint, and civet) and anger eliciting stimuli (i.e. affective pictures and on-road events). We used this knowledge to conduct the fourth user study investigating how the selected scents change the emotional state, well-being, and driving behaviour of drivers in an induced angry state. Our findings enable better decisions on what scents to choose when designing interactions for angry drivers.

The Sense of Agency (SoA) is crucial in interaction with technology, it refers to the feeling of 'I did that' as opposed to 'the system did that' supporting a feeling of being in control. Research in human-computer interaction has recently studied agency in visual, auditory and haptic interfaces, however the role of smell on agency remains unknown. Our sense of smell is quite powerful to elicit emotions, memories and awareness of the environment, which has been exploited to enhance user experiences (e.g., in VR and driving scenarios). In light of increased interest in designing multimodal interfaces including smell and its close link with emotions, we investigated, for the first time, the effect of smell-induced emotions on the SoA. We conducted a study using the Intentional Binding (IB) paradigm used to measure SoA while participants were exposed to three scents with different valence (pleasant, unpleasant, neutral). Our results show that participants? SoA increased with a pleasant scent compared to neutral and unpleasant scents. We discuss how our results can inform the design of multimodal and future olfactory interfaces.

Eating is one of the most multisensory experiences in everyday life. All of our five senses (i.e. taste, smell, vision, hearing and touch) are involved, even if we are not aware of it. However, while multisensory integration has been well studied in psychology, there is not a single platform for testing systematically the effects of different stimuli. This lack of platform results in unresolved design challenges for the design of taste-based immersive experiences. Here, we present LeviSense: the first system designed for multisensory integration in gustatory experiences based on levitated food. Our system enables the systematic exploration of different sensory effects on eating experiences. It also opens up new opportunities for other professionals (e.g., molecular gastronomy chefs) looking for innovative taste-delivery platforms. We describe the design process behind LeviSense and conduct two experiments to test a subset of the crossmodal combinations (i.e., taste and vision, taste and smell). Our results show how different lighting and smell conditions affect the perceived taste intensity, pleasantness, and satisfaction. We discuss how LeviSense creates a new technical, creative, and expressive possibilities in a series of emerging design spaces within Human-Food Interaction.

The human sense of smell is powerful. However, the way we use smell as an interaction modality in human–computer interaction (HCI) is limited. We lack a common reference point to guide designers’ choices when using smell. Here, we map out an olfactory design space to provide designers with such guidance. We identified four key design features: (i) chemical, (ii) emotional, (iii) spatial, and (iv) temporal. Each feature defines a building block for smell-based interaction design and is grounded in a review of the relevant scientific literature. We then demonstrate the design opportunities in three application cases. Each application (i.e., one desktop, two virtual reality implementations) highlights the design choices alongside the implementation and evaluation possibilities in using smell. We conclude by discussing how identifying those design features facilitates a healthy growth of this research domain and contributes to an intermediate-level knowledge space. Finally, we discuss further challenges the HCI community needs to tackle.

There is increasing interest in multisensory experiences in HCI. However, little research considers how sensory modalities interact with each other and how this may impact interactive experiences. We investigate how children associate emotions with scents and 3D shapes. 14 participants (10-17yrs) completed crossmodal association tasks to attribute emotional characteristics to variants of the "Bouba/Kiki" stimuli, presented as 3D tangible models, in conjunction with lemon and vanilla scents. Our findings support pre-existing mappings between shapes and scents, and confirm the associations between the combination of angular shapes ("Kiki") and lemon scent with arousing emotion, and of round shapes ("Bouba") and vanilla scent with calming emotion. This extends prior work on crossmodal correspondences in terms of stimuli (3D as opposed to 2D shapes), sample (children), and conveyed content (emotions). We outline how these findings can contribute to designing more inclusive interactive multisensory technologies.

Overreliance in technology is safety-critical and it is assumed that this could have been a main cause of severe accidents with automated vehicles. To ease the complex task of permanently monitoring vehicle behavior in the driving environment, researchers have proposed to implement reliability/uncertainty displays. Such displays allow to estimate whether or not an upcoming intervention is likely. However, presenting uncertainty just adds more visual workload on drivers, who might also be engaged in secondary tasks. We suggest to use olfactory displays as a potential solution to communicate system uncertainty and conducted a user study (N=25) in a high-fidelity driving simulator. Results of the experiment (conditions: no reliability display, purely visual reliability display, and visual-olfactory reliability display) comping both objective (task performance) and subjective (technology acceptance model, trust scales, semi-structured interviews) measures suggest that olfactory notifications could become a valuable extension for calibrating trust in automated vehicles.

The Sense of Agency (SoA) refers to our capability to control our own actions and influence the world around us. Recent research in HCI has been investigating SoA to provide users an instinctive sense of "I did that" as opposed to "the system did that". However, current agency measurements are limited. The Intentional Binding (IB) paradigm provides an implicit measure of the SoA, however, it is constrained by requiring high visual attention to a "Libet clock" on-screen. In this paper, we extended the timing stimuli through auditory and tactile cues. Our results demonstrate that audio timing through voice commands and haptic timing through tactile cues on the hand, are an effective alternative measure of the SoA using the IB paradigm. They both address current limitations of the traditional method such as visual attention overload and lack of engagement. We discuss how our results can be applied to measure SoA in tasks involving different interactive scenarios such as in Mixed/Virtual Reality.

Cars provide drivers with task-related information (e.g. "Fill gas") mainly using visual and auditory stimuli. However, those stimuli may distract or overwhelm the driver, causing unnecessary stress. Here, we propose olfactory stimulation as a novel feedback modality to support the perception of visual notifications, reducing the visual demand of the driver. Based on previous research, we explore the application of the scents of lavender, peppermint, and lemon to convey three driving-relevant messages (i.e. "Slow down", "Short inter-vehicle distance", "Lane departure"). Our paper is the first to demonstrate the application of olfactory conditioning in the context of driving and to explore how multiple olfactory notifications change the driving behaviour. Our findings demonstrate that olfactory notifications are perceived as less distracting, more comfortable, and more helpful than visual notifications. Drivers also make less driving mistakes when exposed to olfactory notifications. We discuss how these findings inform the design of future in-car user interfaces.

Smell is a powerful tool for conveying and recalling information without requiring visual attention. Previous work identified, however, some challenges caused by user's unfamiliarity with this modality and complexity in the scent delivery. We are now able to overcome these challenges, introducing a training approach to familiarise scent-meaning associations (urgency of a message, and sender identity) and using a controllable device for the scent-delivery. Here we re-validate the effectiveness of smell as notification modality and present findings on the performance of smell in conveying information. In a user study composed of two sessions, we compared the effectiveness of visual, olfactory, and combined visual-olfactory notifications in a messaging application. We demonstrated that olfactory notifications improve users' confidence and performance in identifying the urgency level of a message, with the same reaction time and disruption levels as for visual notifications. We discuss the design implications and opportunities for future work in the domain of multimodal interactions.

The sense of smell is well known to provide very vivid experiences and to mediate a strong activation of crossmodal semantic representations. Despite a growing number of olfactory HCI prototypes, there have been only a few attempts to study the sense of smell as an interaction modality. Here, we focus on the exploration of olfaction for in-car interaction design by establishing a mapping between three different driving-related messages ("Slow down", "Fill gas", "Passing by a point of interest") and four scents (lemon, lavender, peppermint, rose). The results of our first study demonstrate strong associations between, for instance, the "Slow down" message and the scent of lemon, the "Fill gas" message and the scent of peppermint, the "Passing by a point of interest" message and the scent of rose. These findings have been confirmed in our second study, where participants expressed their mapping preferences while performing a simulated driving task.

While there is an increased appreciation for integrating haptic feedback with audio-visual content, there is still a lack of understanding of how to quantify the added value of touch for a user's experience (UX) of multimedia content. Here we focus on three main concepts to measure this added value: UX, emotions, and expectations. We present a case study measuring the added value of haptic feedback for a standardized set of audio-visual content (i.e., short video clips), comparing two haptic stimulation modalities (i.e., mid-air vs. vibro-tactile stimuli). Our findings demonstrate that UX of haptically-enhanced audio-visual content is perceived as a more pleasant, unpredictable, and creative experience. The users' overall liking increases together with a positive change of the users' expectations, independently from the haptic stimulation modality. We discuss how our approach provides the foundation for future work on developing a measurement model to predict the added value of haptic feedback for users' experiences within and beyond the multimedia context.

When designing olfactory interfaces, HCI researchers and practitioners have to carefully consider a number of issues related to the scent delivery, detection, and lingering. These are just a few of the problems to deal with. We present OSpace - an approach for designing, building, and exploring an olfactory interaction space. Our paper is the first to explore in detail not only the scent-delivery parameters but also the air extraction issues. We conducted a user study to demonstrate how the scent detection/lingering times can be acquired under different air extraction conditions, and how the impact of scent type, dilution, and intensity can be investigated. Results show that with our setup, the scents can be perceived by the user within ten seconds and it takes less than nine seconds for the scents to disappear, both when the extraction is on and off. We discuss the practical application of these results for HCI.