# Emotional Response to Vibrothermal Stimuli
## 4 Discussion
### Using Temperature for Affect  
As thermal stimulation has fewer controllable parameters (direction, extent, and rate of change), it may be useful to explore multimodal stimuli for enriched expressiveness and expand the affective region in the V-A plot. [PERSON] et al. suggest combining vibrotactile and thermal stimuli to access a wider range of emotional meaning [5]. In that study, they designed a device where thermal stimulations were conveyed to the palm of the hand. All three parameters in thermal feedback were used: the direction of change (hot and cold), rate of change (1 \({}^{\circ}\)C/s and 3 \({}^{\circ}\)C/s), and extent of change (2 \({}^{\circ}\)C, 4 \({}^{\circ}\)C, 6 \({}^{\circ}\)C, and 8 \({}^{\circ}\)C). They showed a significant impact of temperature on V and no significant effect on A when using +/-4 \({}^{\circ}\)C dynamic thermal stimulation. Their work further suggests that thermal feedback of high V and low A can be conveyed through small (2-4 \({}^{\circ}\)C) warming changes, while a large extent of change (8 \({}^{\circ}\)C) may result in a decrease in V [5]. On the other hand, [PERSON] et al. noted that small dynamic warming stimulations (less than 6 \({}^{\circ}\)C) can lead to low V and high A [12]. In their experiment, thermal feedback was applied to the palm using a custom-built Peltier unit. The current study agrees that there is a significant effect of a change in the direction of temperature on valence and no significant effect on arousal (Table 1). Figure 9 shows that increasing the dynamic temperature (by 4 \({}^{\circ}\)C) generally leads to a decrease in V, which is in contradiction to the findings of [PERSON] et al. [5] and in agreement with [PERSON] et al. [12].  
This contradiction might be due to many factors: (1) the general location of the stimuli on the circumplex model; (2) the extent of change studied; and/or (3) the presentation method used. It is useful to note that the choice of spatiotemporal patterns may influence the quality of emotional response to thermal stimulation. Interestingly, in the current study, certain unique spatiotemporal patterns did demonstrate a pronounced susceptibility to thermal stimulation on both V and A. Additionally, increasing the extent of temperature change may result in higher A, and using smaller (2 \({}^{\circ}\)C) or larger (6 \({}^{\circ}\)C) shifts in temperature may be more effective in registering changes in V than 4 \({}^{\circ}\)C [12]. In addition, [PERSON] et al. points to the effect of the technique of presentation on the emotional response of participants, which is also dependent on the location of the stimulation on the body [7; 12]. Hence, introducing more thermal parameters may lend insight into fine-grained emotional responses.  
[PERSON] et al. previously studied the emotional responses of combined vibrotactile and thermal stimulation with three vibrotactile parameters (frequency, amplitude, and duration) and one thermal parameter (constant temperatures of 20 \({}^{\circ}\)C, 30 \({}^{\circ}\)C, and 40 \({}^{\circ}\)C). They found that constant thermal stimuli generally shift emotional responses without affecting the outcomes from vibrotactile stimulation parameters [32]. This conclusion agrees with the present study (see Table 1 and Figure 9), though a dynamic method of presenting the temperature was used (direction of change variation of 4 \({}^{\circ}\)C with respect to skin temperature). Nevertheless, the effect of certain spatiotemporal patterns does display variations in emotional response to thermal stimulation. This means that intelligently combining vibrotactile and thermal stimulation may increase the range of emotions, as pointed out in previous research [5].