Evaluating Interventions to Reduce Stress

The present work contributes a multidimensional investigation of different approaches aiming to reduce stress. While Chapter 5 concentrates on the exploration of effective stimuli to provide feedback on stress states, in Chapter 6 three concepts of how stressors can be manipulated are validated in the field collecting insightful user feedback. The reasoning for focusing on those constructs which elicit stress in users lays in the conclusion that notifications about stress can lead to opposite effects. In practice, signaling the user that the stress level has risen was seen as critical by participants (see Section 5.3.2), since it could increase one’s stress level instead of reducing it. Consequently, the approach to adjust the stressor had been explored extensively in this work. For this, the first study eliminated stressors as a potential opportunity to reduce subjectively felt stress elicited by interruptions from notifications, response pressure or the fear of missing out. Subsequently, the effects of visualizing stressors had been examined taking two different characteristics. Before the self-report on one’s perceived level of business has been presented publicly requiring the users take action, the visual representation of one’s cognitive load in form of ambient feedback had been evaluated in a semi-public setting.

Referring toRQ3a, there exist several possibilities of which this work varies three means to manipulate stressors, namely the utilization of technological means, the deployment scenario, and the variation of user control. In concrete,

despite the variation in the applied deployment, namely smartphone, ambient display, and manual display, further the privacy continuum has been exploited ranging from private usage (smartphone) through semi-public (ambient display in a shared office) up to public (necklace worn in an university). For the modification of user control the users’ ability to change the stressor manipulation had been varied. For example, the smartphone application had two different modes that delayed notifications for a fixed time interval and one for which the delay could be adjusted.

Suitability of Tactile Feedback In the course of the exploration of feedback for stress states several types of work have been performed involving tactile feedback. Due to its advantages, namely the unobtrusiveness, which also preserves privacy and is less revealing, as well as the unoccupation of this sense by other technology so farRQ2a, this modality was used to design two experiments evaluating the effectiveness of different tactile stimuli. Finding an answer to research questionsRQ2b, initially the effect of presenting vibrotactile feedback in comparison to pressure-based stimulation had been evaluated in a user study.

Since the latter was indicated to evoke only a little less stress in the users when being applied, the third common type of tactile feedback, thermal stimulation, was researched in the subsequent study. Hereby, it was found that an effective feedback stimulus is mild cold and has a high rate of change (RQ2b). Regarding the body location, where users would like to receive the feedback, it showed to depend on whether users valued the privacy preservation and therefore chose hidden spots, such as the back. Unlike others, who appreciated the familiarity and unobtrusiveness when incorporating thermal feedback in existing smart watches or other wrist-worn wearables. However, the participants’ opinions were divided regarding the overall effectiveness of and utility of the approach to notify users about their stress level, which is why I explored the manipulation of the source of stress as another concept.

Effects of Manipulating Stressors One of the essential outcomes of the three performed evaluation studies was that users partly had the feeling that the manipulation of the stressor affected their stress level (cf., Section 6.2) and their perceived feeling of being busy (cf., Section 6.4) positively. Although there could not be shown significant differences for the stress assessments, the fact that users subjectively felt less stressed or calmed down is a notable effect (RQ3b). As another interesting finding tackling research questionRQ3cusers reported that they were encouraged to reflect about the manipulated stressors. In practice, the smartphone usage and notification management was viewed more critically throughout the study participation. Further, the feedback presented on the ambient display supported the participants in listening to their own body signals indicating

mental overload. Similarly, the adjustment of one’s level of business assumed that users became aware of how much they actually felt stressed or rushed. Thus, not only the self-reflection, but moreover the increased awareness of sources of stress made the stressor manipulation a successful stress-mitigating technique.

Interestingly, the reflective potential of this approach was shown to exceed and even affected the mutual consideration among colleagues as the lastly performed study could show. In this context, it was revealed that visualizing the stressor stimulated insightful conversation and could even facilitate the understanding of the participants’ kids regarding their parents’ stress state. For this, the effects of manipulating stressors can be regarded as overall positive ranging from subjectively perceived less stress through increased awareness of stressors up to the facilitation to reflect about oneself and even others.

Respecting Privacy in Stress-aware Systems As has been shown to be particularly relevant for studies involving the public (or semi-public) representation of one’s mental state, the preservation of privacy plays a key role in the design of stress-aware interactive systems being addressed byRQ3d.

Moreover, presenting sensitive private information unobtrusively is important, since it had been revealed that individuals have concerns disclosing their stress state in front of others as an outcome of the research probes focalizing the visualization of stressors. However, thinking of the presentation of tactile feedback and in particular thermal stimuli (cf., Chapter 5), the approach to discreetly notify about one’s stress has not been shown to be promising. Whereas exploiting the main advantage of thermal feedback by combining it with the manipulation of stressors could be desirable. Reviewing the findings from Chapter 6, it can be obtained that granting users as much freedom to utilize the technology according to their needs and requirements seems to be successful for causing a feeling of privacy due to the maintained control. Correspondingly, the transparency of what data is being recorded, what is being used for, and where it is being stored must be provided when incorporating physiological data. As the study participants emphasized, the fear of seeing one’s data abused is a prevalent thread when dealing with technology. Thus, to build trust and support the users’

confidence, interactive systems must provide comprehensive explanations for the aforementioned questions and further let users maintain control, when aiming for successful and effective systems.