# A Controlled Study on Evaluation of Thermal Stimulation Influence on
Affective Measures of Uninformed Individuals
††thanks: Authors 1 are with the Department of Mechanical Engineering at
University of South Florida. Authors 2 are with the Department of Psychology
at University of South Florida.

Mehdi Hojatmadani1 Samantha Shepard2 Kristen Salomon2 Kyle Reed1

###### Abstract

Although the relationship between temperature and emotional states has been
investigated in the field of haptics, it remains unknown if, or in what
direction, temperature affects emotional states. We approach this question at
the intersection of haptics and psychology using a custom-built thermal device
and emotional responses based on photos from the International Affective
Picture System (IAPS) library. Unlike past research, this study incorporates
deception and a control (i.e., neutral temperature) condition. One hundred and
twenty naive subjects reported their emotional responses to fifty-six images
varying on normative arousal and valence ratings while being exposed to a cool
(30°C), neutral (33°C), or warm (36°C) temperature applied to the upper back.
Participants exposed to warm temperatures reported higher arousal ratings in
some image categories than participants exposed to neutral or cool
temperatures. Valence ratings were decreased in warm conditions compared to
neutral conditions. The emotion wheel was used as a complementary method of
affective response measurement, and exploratory analysis methods were
implemented. Although the valence and arousal showed statistical significance,
the emotion wheel results did not demonstrate any significant differences
between the temperature conditions.

###### Index Terms:

component, formatting, style, styling, insert

##  I Introduction

Temperature plays a vital role in human survival. Thermoregulation attunes
body temperature to the environment, utilizing mechanisms such as sweating or
shivering [1]. Temperature has long been posited to play a role in emotions
[2]. Most research has focused on the effect of emotional states on body
temperature, while less work has examined the effects of body temperature on
resultant emotional states. The present study examines the effects of local
thermal stimulation on emotional experiences.

Evidence suggests that people can communicate emotions such as anger, fear,
and love through physical touch [3]. Similarly, greater emotional pleasantness
and excitement are associated with less roughness and more fluidity while
interacting with objects through touch [4]. Given these findings, it seems
likely that affective measures may also be associated with thermal sensation
[5].

Emotions can be described quantitatively based on two measures: valence and
arousal. Positive/negative valence describes the pleasantness/unpleasantness
of an emotion, while high/low arousal describes the exciting/calming degree of
the emotion. For example, anger is an emotion with negative valence and high
arousal, while feeling peaceful is associated with positive valence and low
arousal.

###  I-A Effect of emotional experience on body temperature

The effect of emotions on body temperature is well established. Stress is
associated with small increases in central body temperature, referred to as
stress-induced hyperthermia [6]. Further, specific emotional states are
associated with changes in skin temperature [7, 8], which is thought to
reflect changes in cutaneous circulation [9]. Given these bodily changes, it
is perhaps not surprising that individuals associate specific emotions with
distinct bodily patterns of warm and cool, or “temperature maps” [10]. For
example, anger is associated with heat in the head, torso, and arms, whereas
anxiety is associated with heat mainly in the chest and warmth in the neck and
gut. Sadness is also associated with warmth in the face, neck, and chest but
coolness in the arms and legs. In contrast, depression is associated only with
coldness in the head and extremities. Thus, emotional experience involves
changes in body temperature and sensations of temperature, which suggests that
changes in body temperature may affect emotional experience.

###  I-B Effect of Temperature Changes on Emotional Experience

Temperature’s effects have been examined as either the emotional
interpretation of the temperature itself or as the effects of temperature on
broader emotional experience. Regarding the former, warm stimuli are generally
perceived as positive in emotional valence, and cool stimuli are perceived as
unpleasant in valence [11]. Evidence is mixed regarding the latter and the
focus of the present study.

A study of the effect of a combination of haptic and visual stimuli on
altering emotional ratings demonstrated that temperature can increase the
available range of emotional states [12]. Warm and cool temperatures
effectively communicate positive and negative meanings and improve the quality
of communicated emotions [13]. It was demonstrated that warmth stimulation
increases emotional arousal while cool stimulation affects perceptions of the
pleasantness of the message, also known as valence. For example, El Ali et al.
[14] played a series of emotionally neutral audio messages to participants
while wearing a thermally active vest, applying a temperature gradient on
their bodies. The temperature changes in positive (warm) and negative (cool)
directions influenced the valence and arousal levels of the messages they
heard. Warming temperature has been shown to elicit greater emotional arousal
than cooling temperatures, while individuals viewed images that elicit
specific emotions [15, 16]. It was also demonstrated that a 3°C temperature
change increased arousal levels compared to no temperature change.

Temperature perception can be manipulated to create various sensations and
emotions, for instance, creating a constant cooling sensation [17, 18, 19]
when the average temperature of the stimulated area is not changing or
creating a pain sensation [20] using a combination of hot and cold bars where
the temperature of each bar is below the pain threshold. Temperature is also
useful in modulating affective states when combined with other sensory
modalities. Additionally, therapeutic manipulation of brain temperature is
hypothesized to decrease depressed mood and may be effective in treating
psychological disorders, such as mania [21]. A recent study of whole-body
cooling and warming found resultant activation not only in the thermosensory
cortex (left dorsal posterior insula) but also in limbic structures (the left
amygdala and the bilateral retrosplenial cortices) associated with autonomic
function and emotion [22].

One of the instances of the effect of temperature on emotions was demonstrated
by a test designed by De Wall and Bushman [23] in which aggression was
evaluated after being exposed to words related to temperature. The results
demonstrated that the words associated with heat could invoke aggressive
thoughts and hostile perceptions, which reflect high-arousal emotion. Janssen
et al. [24] studied the effect of temperature on depression to determine
whether thermal stimulation could be used as a treatment method for major
depressive disorder. The results indicated that a 6-week hyperthermia
intervention of increasing the body temperature decreased the depression
symptoms relative to a control condition. Another study [25] demonstrated that
whole-body hyperthermia treatment reduced depression in the participants who
were not given SSRI medications. Notably, deception was not used in these
experiments, which could have influenced participant responses. Participants
were aware that a thermal stimulus was present and likely could have deduced
that the experiment was testing if temperature could influence their emotions.

Although the previously discussed research reveals a strong connection between
temperature and emotion, the efficacy of local thermal stimulation needs to be
thoroughly investigated.

##  II The Present Study

Our study extends extant research by investigating how temperatures (warm or
cool) may affect the intensity and pleasantness of emotion by applying thermal
stimulus to local areas of the body. In this study, the thermal actuator was
in contact with the skin on the back of the neck. Since the neck does not
typically experience external thermal stimuli, unlike hands, and temperature
sensation is not as localizable as other senses, it is hypothesized that the
sensation of the temperature will be more pronounced in this area. Another
distinction of this work from similar studies is that participants were not
aware of the study’s purpose in this study, making the results less
susceptible to expectation bias. We hypothesize that placing the
thermoelectric device on the back of the neck reduced the possibility of
participants realizing the purpose of the study since they were not required
to move their hands on/off the device actively. Another improvement in this
study is the addition of a control condition, where participants’ ratings of
images in cool and warm conditions were compared to the neutral temperature
condition. This is in contrast to the existing studies where participants’
valence and arousal ratings of each image were compared to the rated IAPS
library ratings [16].

We hypothesize that the temperature condition will affect the SAM valence and
arousal rating for the images in warm and cool conditions compared to the
neutral condition. Participants will also be asked to report their emotions
using Geneva Emotion Wheel as a complementary method of reporting their
affective state.

##  III Methods

###  III-A Participants

Participants were recruited from the undergraduate students participant pool
in the Department of Psychology at the University of South Florida. One
hundred and twenty-nine individuals participated in the study. The experiments
were completed between August 2019 and November 2019. Nine participants’ data
were dismissed because the correct temperature was not applied due to
equipment malfunction, leaving 41 participants in the cool condition, 37 in
the warm condition, and 42 in the neutral condition.

The experimental protocol and the consent form were approved by the University
of South Florida’s Institutional Review Board. Written informed consent was
obtained from all the subjects prior to participation. All research was
performed in accordance with the relevant guidelines and regulations.

###  III-B Experimental Setup

The experimental setup (Figure 1) is comprised of three main components: the
thermoelectric device, the temperature controller, and the graphical user
interface. In this study, a Tegway flexible thermoelectric device [26] was
utilized to create temperature gradients. In order to control the skin
temperature during the experiment, the temperature of the other side of the
thermoelectric needs to be maintained at a low temperature. An active cooling
system was designed to be attached to the thermoelectric device for this
purpose. A system of water block and hoses was used to supply cold water to
the hot side of the device. The thermal device was held in place using a
wearable brace, securing the device’s position. The thermoelectric temperature
at the skin interface was measured using an NTC 10K ohm thermistor. The power
supply to the thermoelectric was controlled using a Pololu Simple Motor
Controller 18v7 and an Arduino Uno microcontroller. The actuator was able to
apply thermal cues with an accuracy of $\pm$0.5 °C. The motor controller was
powered through a power supply (B$\&$K Precision 1666). A graphical user
interface (GUI) was developed in MATLAB to display the images and record the
affective responses. MATLAB was communicating with the Arduino through a
serial port to apply the thermal cues and automate the experiment.

Figure 1: Experimental setup. A participant wearing the thermal actuator on
the back of the neck while rating the image using the Geneva Emotion Wheel.

###  III-C Study Design

Participants viewed a series of images and self-reported their affective
response to each using the graphical user interface. Participants were
randomly assigned to experience one of three temperature conditions. This
approach was adapted to avoid raising participants’ suspicion about the
study’s goal, as this was the case in a pilot study where temperature
condition was used as a within-subject factor. Images were selected based on
the valence and arousal ratings of the IAPS normative rates such that the
standard deviation of the means for the selected images was minimized. Each
participant viewed eight images in each of the seven image categories.

###  III-D Material

Affective Stimuli: Photos from the International Affective Picture System
(IAPS; [27]) were shown to participants. The IAPS is a pictorial library of
images that have been demonstrated to elicit specific emotions. Each picture
is accompanied by a normative mean valence and arousal level. We categorized
pictures into nine categories based on three levels of low, medium, and high
valence and arousal normative scores. These levels were selected to create the
most distinct set of images from each other. However, given the selection
criteria, two categories did not contain a sufficient number of images
(negative valence-low arousal, N = 5 images, and neutral valence-high arousal,
N = 3 images). Thus, a subset of eight images was selected from the remaining
seven categories. To create relatively homogenous categories, images for each
category were selected to minimize the standard deviation of ratings within
each category using a custom MATLAB optimization script. The depiction of each
image category location on the valence-arousal plane and the normatively rated
valence and arousal levels are shown in Table I.

TABLE I: Normative rating of valence and arousal in each image category (top)
and mean of participants’ response for those categories (bottom).

|  | - | Valence | +
---|---|---|---|---
High |  | Normative Rating
---
Responses
| [2.18, 6.32]
---
[2.09, 5.53]
|  | [7.33, 6.00]
---
[6.57, 4.63]
Arousal |  | Normative Rating
---
Responses
| [2.93, 5.03]
---
[3.09, 4.42]
| [5.12, 4.49]
---
[5.23, 3.61]
| [7.53, 4.60]
---
[6.93, 3.80]
Low |  | Normative Rating
---
Responses
|  | [5.21, 3.43]
---
[5.18, 3.30]
| [7.3, 3.61]
---
[6.75, 3.30]

Ratings of IAPS photos: The self-assessment Manikin (SAM; [28]) was used to
collect participants’ valence and arousal ratings on a nine-point scale. SAM
ranges from a smiling, happy figure to a frowning, unhappy figure when
representing the valence dimension and ranges from an excited, wide-eyed
figure to a relaxed, sleepy figure for the arousal dimension. The SAM also
includes a dominance rating scale. However, because valence and arousal can
explain most of the variations in emotions [29], the dominance rating was not
used in the data collection process.

Geneva Emotion Wheel: Emotional responses were collected using the Geneva
emotion wheel [30]. This emotion wheel is comprised of 16 emotions forming a
circle with neutral in the middle. The concept of the emotion wheel is that
the further away from the center of the circle, the more intense the emotions
become. Therefore, participants select the biggest circle on the joy axis if
they feel much joy. The emotion wheel could be considered a more direct report
method as there are distinct emotions on the wheel versus SAM where emotions
are broken into their components.

###  III-E Procedure

Participants were informed that the study aimed to evaluate emotion while
recording their physiological responses. They were briefed about the procedure
of the study. This provided adequate time for their body to acclimate to the
room temperature. After the informed consent was signed and briefing was
completed, the thermoelectric device was placed on the back of the neck
approximately at the C7 to T2 vertebrae level. Research personnel placed two
ECG electrodes onto the collarbone and torso, where the electrodes were
attached to physiological recording equipment. However, no physiological
measures were collected. The physiological recording equipment served as a
distraction from the study’s true purpose, as participants were led to believe
the thermoelectric device was yet another physiological recording device.

Participants sat in a chair in front of a computer and were given instructions
on how to complete the self-assessment manikin and the emotion wheel.
Participants were led through several practice trials to ensure they
understood the emotion rating procedure. Next, each participant was randomly
assigned to one of the three temperature conditions: cool (30°C), neutral
(33°C), and warm (36°C). Participants viewed each of the 56 selected IAPS
images for 6 seconds, displayed in random order on the computer screen, and
were asked to rate their emotions using the SAM and the emotion wheel. The
temperature was constant and was applied throughout the experiment. The trial
practice and the main experiment lasted approximately 35 minutes.

Once all images were viewed and rated, participants were probed for suspicion
of the cover story, fully debriefed as to the nature of the deception, and
asked if, after knowing the true nature of the study, they would like to have
their data removed or to allow the researcher to retain it for analysis (in
accordance with the university’s IRB policy). No subject requested their data
to be removed. No subject realized the true nature of the study.

##  IV Results

Two mixed-design factorial 3 (Temperature) x 7 (image category) ANOVA tests
were conducted with temperature as the between-subjects variable, image
category as the within-subjects variable, and image ratings as the dependent
variable. Bonferroni-corrected post-hoc comparisons were completed when
omnibus F-tests showed statistical significance. Statistical significance was
determined using an alpha of 0.05. Analyses were conducted using SPSS 24. The
single asterisk in the figures represents 0.01 $<$ p $<$ 0.05.

###  IV-A Self-Assessment Manikin

Figure 2: SAM rating responses for valence and arousal. Statistical
significance is demonstrated on the plots with the asterisks. The error bars
represent the standard error values.

The ANOVA test results for arousal ratings demonstrated a main effect of
temperature (F(2,116) = 3.10, p = 0.048). Arousal ratings across the image
category were significantly lower in the cool condition (M = 3.75, SE = 0.21)
than in the warm condition (M = 4.52, SE = 0.22). These two conditions were
not rated statistically different from the control (neutral) condition. Post-
hoc tests indicated that participants’ arousal ratings of positive valence-low
arousal, positive valence-medium arousal, and neutral valence-medium arousal
categories were affected by temperature conditions. The warm condition ratings
were higher than the cool condition in the mentioned conditions. The trends
are shown in Figure 2.

The test showed a main effect of temperature on valence rating (F(2,117) =
3.43, p = 0.036). Images were rated lower in the warm condition compared to
the neutral condition. There was no statistically significant interaction
between image category and temperature on valence ratings (F(12,696) = 0.77, p
= 0.638). The summary of ratings can be seen in Figure 2. Valence and arousal
ratings for each image category and the normative ratings for comparison can
be found in Table I.

###  IV-B Geneva Emotion Wheel

Analyzing emotion wheel data is a challenging task mainly because of the
absence of a standard approach in psychology for analyzing this type of data.
One obstacle in analyzing emotion wheel data is that the data cannot be
considered entirely discrete or continuous. Another hurdle is that the circles
in proximity to each other share the same valence/control levels. On the other
hand, the fact that it is a circle adds to the challenge of defining a point
of reference to quantify emotions. This section presents different approaches
devised to analyze the emotion wheel data.

The first approach was to analyze the emotions based on the emotion category
and intensity as discrete values. This approach divided responses into 65
categories (16 x 4 + 1), corresponding to 16 emotions with four intensity
levels and one neutral. Two other levels of categorization were the image
category and the temperature conditions (7 x 3). Since some categories had low
response frequency, to eliminate outliers, frequency responses that were less
than 15 responses (out of 6,720 total) were removed from the data set to
decrease low-confidence results. A Chi-Square test was conducted to determine
whether there was a significant difference between the emotional responses
between image categories and temperature conditions. The results did not
indicate a significant difference between temperature conditions for different
image categories ($\mbox{$\chi^{2}=(244,N=123)=250.98$},\mbox{p=0.375}$).

Another approach to analyzing emotion wheel data was to define the geometrical
metric. Since the emotion wheel benefits from geometry in defining emotions,
it seems logical to pursue the same method in evaluating the results. The
approach taken here was to analyze the responses in terms of their angle on
the wheel, which corresponds to the type of emotion, and the distance from the
center of the circle, which corresponds to the intensity of the emotion. Each
participant’s average response angle was calculated for each image category.
Later, the resulting value was continuous, so it can be analyzed using
standard parametric statistical methods. The same process was performed on the
distance of the responses to calculate the mean distance for each image
category for every participant. This way, a mixed-design analysis of variance
(ANOVA) was performed on each data set. In this analysis, the temperature
condition was the between-subject independent variable. The image category was
a within-subject independent variable with angle/distance mean values as the
dependent variable. The results did not demonstrate a significant difference
between temperature conditions (F(2,122)=0.219, p=0.804). A similar method on
the distance of the responses was performed, which did not result in a
significant difference between temperature conditions (F(2,126)=0.034,
p=0.967).

The results of emotion wheel responses are illustrated in Figure 3. On these
figures, the frequency of each emotion is proportional to the height of the
bars. A chi-square test of independence was performed to examine the relation
between temperature conditions and self-reported emotions. The first
independent variable was the emotion category, which combined the rated
emotion and its image category. The other independent variable was the
temperature condition. The dependent variable was the frequency of the
responses.

After removing the frequencies that occurred less than 5 times, 54 emotion
categories were left with three temperature conditions. Test results did not
demonstrate a statistically significant difference between independent
variables ($\mbox{$\chi^{2}(106,N=6160)=110.95$},\mbox{p = 0.352}$). The
results for each temperature condition and emotion are illustrated in Figure
3.

Figure 3: Emotion wheel responses for three temperature conditions with a
schematic of the emotions and their locations on the emotion wheel. Emotion
responses with a frequency response of less than 5 are not included.

##  V Discussion

In this study, the contribution of temperature on affective measures was
investigated. Naive participants reported their emotions through SAMS after
viewing a series of images from the IAPS library while experiencing a cool
(30°C), neutral (33°C), or warm (36°C) temperature on the back of their neck.
Geneva emotion wheel was used as a complementary method for evaluating
affective measures.

In all image categories, the arousal ratings ascended from cool to neutral and
neutral to warm conditions. Warm temperature ratings for arousal were
significantly higher than the cool temperature in image categories, where the
arousal ratings were low or medium (image categories 1, 2, and 5). We
hypothesize that the absence of significant difference between high-arousal
categories was because the arousal rating for those categories was already
high; therefore, the warm temperature needed to increase the affective measure
level to the extreme value, which was not plausible with the given temperature
conditions. The obtained result agrees with Akazue et al. [16], whose findings
showed that thermal stimulation increases the arousal rating in images with
neutral to low arousal. However, it is worth mentioning that the results
obtained in this work are different from the mentioned study regarding the
statistical method. Akazue et al. considered the control condition as the
normative ratings of the IAPS images, while in this study, the control
condition was the neutral temperature condition using a more direct
comparison. By comparing the obtained valence-arousal responses and the
associated emotion on the emotion circumplex, one can observe that warm
temperature moved the affective state from emotions like “hopeful” to “feel
well”. The cool temperature most effectively changed participants’ arousal
levels, where images elicited neutral arousal emotions. This effect diminishes
for unpleasant emotions (categories 1 and 2). Moreover, the difference between
valence ratings for neutral and warm conditions is clear evidence of the
effect of temperature on affective measures. Warm temperature decreased the
pleasantness of the ratings. This difference is highest for image category 2
and can be seen in Figure 2.

A comparison of results from Figure 2 and Table I shows that the valence
responses were more consistent with normative ratings from the IAPS library
for unpleasant and neutral images. The variability of the responses also
decreased for valence ratings compared to the arousal ratings. Although the
temperature condition affected the valence ratings, overall, this difference
was not reflected within each image category. We hypothesize that a more
intense thermal stimulus could affect participants’ responses on a greater
scale. However, there are challenges associated with this approach that
require making a trade-off between different aspects of the test design. The
lack of a universal reference point for thermal perception makes temperature a
more personal stimulus. Due to the variability of skin temperature, skin type,
and metabolism between participants, one can not guarantee a similar thermal
perception intensity for all participants. Another challenge is that
increasing the temperature intensity could affect the deception method and
lead individuals to realize the purpose of the study. Another contributor is
the thermal adaptation over the course of the test. Individuals might lose
sensitivity to the applied temperature over time, affecting their responses.

Different exploratory statistical analysis methods are introduced for
analyzing the emotion wheel data. The results of the emotion wheel did not
demonstrate any effect of temperature on responses. This result does not seem
surprising since the images were selected based on their valence and arousal
ratings and not by their relation to the same emotional state, e.g., “anger”
or “sadness”. We hypothesize that selecting a more tailored set of images for
the emotion wheel can evaluate the role of temperature stimulation on emotions
more accurately.

##  VI Conclusion

Results demonstrated that warm temperature increased the arousal ratings of
images with low to neutral arousal levels compared to cool temperature. These
changes occurred for images with positive valence. The results are consistent
with similar studies in the field [16, 12, 31]. In these studies, it was shown
that warm temperatures led to an increase in arousal ratings. The difference
between the previous studies and this study is the location of the thermal
actuator and the use of the deception method, consequently minimizing the
confirmation bias. The addition of the control condition is another
improvement of this study compared to Akazue et al.’s approach [16].

Analyzing the emotion wheel data was challenging since available non-
parametric statistical methods are unsuitable for analyzing the collective
interaction between all emotions and temperature conditions, given the mixed-
design nature of data analysis (presence of within-subject and between-subject
variables). Implementing a fully within-subject study design will alleviate
these concerns. However, it will increase the experiment length and
confirmation bias since participants will need to go through all temperature
conditions.

The role of emotions in haptic interactions has been an underinvestigated
research topic in the haptics community. As commercialized haptic products
become more ubiquitous, studying how each haptic modality can affect users’
emotions can unveil the potential of haptic technology. As discussed in this
work, the extensive interactions between temperature and emotions show how
these two aspects are intertwined and how they can affect our body and mind.
Among these, thermal haptic cues seem to have the most direct impact on
affective measures to the extent that they could compete with medicinal
methods [25]. This emphasizes the importance of this line of research and its
potential to impact people’s lives. Studies similar to the work presented can
provide a clearer picture of how to utilize haptic capabilities to increase
haptic products’ impact.

## Acknowledgments

This material is based upon work supported by the National Science Foundation
under Grant Number IIS-1526475.

## References

  * [1] W. B. Liedtke, “Deconstructing mammalian thermoregulation,” _Proceedings of the National Academy of Sciences_ , vol. 114, no. 8, pp. 1765–1767, 2017.
  * [2] L. H. Ziegler and P. T. Cash, “A study of the influence of emotions and affects on the surface temperature of the human body,” _American Journal of Psychiatry_ , vol. 95, no. 3, pp. 677–696, 1938.
  * [3] M. J. Hertenstein, D. Keltner, B. App, B. A. Bulleit, and A. R. Jaskolka, “Touch communicates distinct emotions.” _Emotion_ , vol. 6, no. 3, p. 528, 2006.
  * [4] K. Drewing, C. Weyel, H. Celebi, and D. Kaya, “Feeling and feelings: Affective and perceptual dimensions of touched materials and their connection,” in _2017 IEEE World Haptics Conference (WHC)_. IEEE, 2017, pp. 25–30.
  * [5] F. Barbosa Escobar, C. Velasco, K. Motoki, D. V. Byrne, and Q. J. Wang, “The temperature of emotions,” _PloS one_ , vol. 16, no. 6, p. e0252408, 2021.
  * [6] T. Oka, “Stress-induced hyperthermia and hypothermia,” _Handbook of clinical neurology_ , vol. 157, pp. 599–621, 2018.
  * [7] P. Ekman, R. W. Levenson, and W. V. Friesen, “Autonomic nervous system activity distinguishes among emotions,” _science_ , vol. 221, no. 4616, pp. 1208–1210, 1983.
  * [8] R. W. Levenson, P. Ekman, and W. V. Friesen, “Voluntary facial action generates emotion-specific autonomic nervous system activity,” _Psychophysiology_ , vol. 27, no. 4, pp. 363–384, 1990.
  * [9] M. Elam and B. Wallin, “Skin blood flow responses to mental stress in man depend on body temperature,” _Acta physiologica scandinavica_ , vol. 129, no. 3, pp. 429–431, 1987.
  * [10] L. Nummenmaa, E. Glerean, R. Hari, and J. K. Hietanen, “Bodily maps of emotions,” _Proceedings of the National Academy of Sciences_ , vol. 111, no. 2, pp. 646–651, 2014.
  * [11] G. Wilson and S. A. Brewster, “Multi-moji: Combining thermal, vibrotactile & visual stimuli to expand the affective range of feedback,” in _Proceedings of the 2017 CHI Conference on Human Factors in Computing Systems_ , 2017, pp. 1743–1755.
  * [12] M. Halvey, M. Henderson, S. A. Brewster, G. Wilson, and S. A. Hughes, “Augmenting media with thermal stimulation,” in _International Conference on Haptic and Audio Interaction Design_. Springer, 2012, pp. 91–100.
  * [13] K. Suhonen, S. Müller, J. Rantala, K. Väänänen-Vainio-Mattila, R. Raisamo, and V. Lantz, “Haptically augmented remote speech communication: a study of user practices and experiences,” in _Proceedings of the 7th Nordic conference on human-computer interaction: making sense through design_ , 2012, pp. 361–369.
  * [14] A. El Ali, X. Yang, S. Ananthanarayan, T. Röggla, J. Jansen, J. Hartcher-O’Brien, K. Jansen, and P. Cesar, “Thermalwear: Exploring wearable on-chest thermal displays to augment voice messages with affect,” in _Proceedings of the 2020 CHI Conference on Human Factors in Computing Systems_ , 2020, pp. 1–14.
  * [15] M. Akazue, M. Halvey, and L. Baillie, “Using thermal stimuli to influence affect in different picture display sizes,” _Personal and Ubiquitous Computing_ , vol. 21, no. 4, pp. 739–759, 2017.
  * [16] M. Akazue, M. Halvey, L. Baillie, and S. Brewster, “The effect of thermal stimuli on the emotional perception of images,” in _Proceedings of the 2016 CHI Conference on Human Factors in Computing Systems_ , 2016, pp. 4401–4412.
  * [17] M. Hojatmadani and K. Reed, “Asymmetric cooling and heating perception,” in _International Conference on Human Haptic Sensing and Touch Enabled Computer Applications_. Springer, 2018, pp. 221–233.
  * [18] A. Manasrah, M. Hojatmadani, R. Guldiken, and K. Reed, “Computational analysis of asymmetrically applied hot and cold stimuli,” _International Journal of Engineering Research & Innovation_, vol. 11, no. 2, pp. 18–27, 2020.
  * [19] M. Hojatmadani, “Interrelation of thermal stimulation with haptic perception, emotion, and memory,” Ph.D. dissertation, University of South Florida, 2021.
  * [20] A. Craig and M. Bushnell, “The thermal grill illusion: unmasking the burn of cold pain,” _Science_ , vol. 265, no. 5169, pp. 252–255, 1994.
  * [21] A. J. Salerian, N. G. Saleri, and J. A. Salerian, “Brain temperature may influence mood: a hypothesis,” _Medical Hypotheses_ , vol. 70, no. 3, pp. 497–500, 2008.
  * [22] H. Oi, T. Hashimoto, T. Nozawa, A. Kanno, N. Kawata, K. Hirano, Y. Yamamoto, M. Sugiura, and R. Kawashima, “Neural correlates of ambient thermal sensation: an fmri study,” _Scientific reports_ , vol. 7, no. 1, pp. 1–11, 2017.
  * [23] C. N. DeWall and B. J. Bushman, “Hot under the collar in a lukewarm environment: Words associated with hot temperature increase aggressive thoughts and hostile perceptions,” _Journal of Experimental Social Psychology_ , vol. 45, no. 4, pp. 1045–1047, 2009.
  * [24] C. W. Janssen, C. A. Lowry, M. R. Mehl, J. J. Allen, K. L. Kelly, D. E. Gartner, A. Medrano, T. K. Begay, K. Rentscher, J. J. White _et al._ , “Whole-body hyperthermia for the treatment of major depressive disorder: a randomized clinical trial,” _JAMA psychiatry_ , vol. 73, no. 8, pp. 789–795, 2016.
  * [25] K.-U. Hanusch, C. H. Janssen, D. Billheimer, I. Jenkins, E. Spurgeon, C. A. Lowry, and C. L. Raison, “Whole-body hyperthermia for the treatment of major depression: associations with thermoregulatory cooling,” _American Journal of Psychiatry_ , vol. 170, no. 7, pp. 802–804, 2013.
  * [26] C. S. Kim, G. S. Lee, H. Choi, Y. J. Kim, H. M. Yang, S. H. Lim, S.-G. Lee, and B. J. Cho, “Structural design of a flexible thermoelectric power generator for wearable applications,” _Applied Energy_ , vol. 214, pp. 131–138, 2018.
  * [27] P. J. Lang, M. M. Bradley, B. N. Cuthbert _et al._ , “International affective picture system (iaps): Technical manual and affective ratings,” _NIMH Center for the Study of Emotion and Attention_ , vol. 1, pp. 39–58, 1997.
  * [28] M. M. Bradley and P. J. Lang, “Measuring emotion: the self-assessment manikin and the semantic differential,” _Journal of behavior therapy and experimental psychiatry_ , vol. 25, no. 1, pp. 49–59, 1994.
  * [29] J. A. Russell, “A circumplex model of affect.” _Journal of personality and social psychology_ , vol. 39, no. 6, p. 1161, 1980.
  * [30] V. Sacharin, K. Schlegel, and K. R. Scherer, “Geneva emotion wheel rating study,” 2012.
  * [31] K. Salminen, V. Surakka, J. Raisamo, J. Lylykangas, J. Pystynen, R. Raisamo, K. Mäkelä, and T. Ahmaniemi, “Emotional responses to thermal stimuli,” in _Proceedings of the 13th international conference on multimodal interfaces_ , 2011, pp. 193–196.