# Emotional Response to Vibrothermal Stimuli
## 2 Materials and Methods
### Procedure  
Each participant was presented with 48 different spatiotemporal vibrotactile patterns (12 vibration patterns, each at 2 different durations), and a cooling or warming thermal sensation (12 \(\times\) 2 \(\times\) 2 = 48). Immediately following each pattern presentation, participants rated their emotional response in terms of valence and arousal using a 7-point Likert scale to provide consistent psychometric measurements. Moreover, following each pattern presentation, participants rated the intensity (warmth or coolness) of the thermal stimulation using a 9-point Likert scale. Recording the sensation of temperature allowed for the verification of whether participants perceived the thermal changes correctly and allowed for the assessment of any device malfunctions. Participants were asked to close their eyes and listen to white noise via headphones during each pattern presentation to avoid external visuals and actuator noise that could have influenced emotional response. Stimuli were presented as follows: first, participants were requested to place the ventral side of their bare, non-dominant wrist on the Embr wave bracelet, attached to a flat surface, for a period of 7 s, for the device and skin temperatures to acclimate. This was followed by activating the white noise and initiating thermal stimulation. After waiting 2 s for thermal adaptation to reach the peak temperature, the spatiotemporal vibrotactile pattern was initiated with either the short or long duration. On completion of the pattern, the thermal stimulation and white noise was stopped. No pattern was repeated for a subject during the study. The sequential repetition of warm signals may cause issues, preventing the device from cooling; hence, it was necessary to randomize the thermal signals accordingly. The experimental setup is depicted in Figure 3, the vibrotactile patterns used are shown in Figure 4 and the experimental procedure is explained in Figure 5.  
Figure 3: Sketch of the experimental set-up: The subject (**left**) is sitting on the Haptic Chair (1) and has their non-dominant hand placed on the Embr wave bracelet (2) affixed to the table. The conductor (**right**) controls the haptic feedback via the computer and thermal feedback using the Embr wave smartphone app. During each trial, white noise is played to the subject using the headphones (3). At the end of each trial, the subject documents his or her response in the form provided. The vibrotactile patterns in Figure 4, are based on previous work that used symbolic spatiotemporal cues to evoke the six basic emotions: 'happy','sad','surprise', 'anger', 'disgust', and 'fear'. Such patterns are considered higher order; they leverage abstraction based on the emotions they elicit from the participants without any training or paired stimulus [23], rather than only varying basic parameters such as amplitude or frequency. It was also found that the duration of presentation had a significant impact on the emotional response of participants [23]; hence, it was used as a parameter in this experiment. Two durations were chosen: 100 ms (short) and 1000 ms (long). The back was chosen as an appropriate body site to present the patterns to enable uniform presentation of the twelve spatiotemporal patterns. In general, thermal feedback has the following parameters: direction of change (hot or cold), rate of change (how fast the temperature changes), and extent of change (the magnitude/intensity of thermal change). In the current experiment, the effect of change in the direction of thermal feedback (in combination with vibrotactile stimulation) was studied. Previous researchers have used either the dominant [5] or non-dominant arm [18; 35] for perceptual studies, but to ease the recording of subject responses, this study used the non-dominant arm. The bracelet provides thermal stimulation using the dynamic method in which the target temperature is reached during presentation, i.e., the temperature is not pre-adjusted.