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Psychological and neural basis of viral online internet challenges: A review

Authors:
  • Agricultural Development Trust

Abstract

Psychology and human neural response are centrally associated with social media interaction. An increase in social media use in recent years has been associated with an increase in the number of internet viral trends. The number of internet challenges has been engaging millions of people to take part in it. In this article, we are trying to focus on human behavior and its neural basis of making internet trends viral. Dopaminergic pathways and one's social dominance have been keen role players in this. The feedbacks and increased reaction on one's uploaded post that sums up increased peer attention on social media can be linked with dopamine pleasures and the reward cycle. Dopaminergic reinforcement triggers user tagging multiple other users for taking up challenge. Challenges and trends involved displaying physical fitness provides one with its increased social ranking as it can be traced with fittest having advantages of social dominance within peers. Cortisol response may play an important role in negative domain response. Hence activation of dopaminergic pathway and benefit of elevated social ranking can be the reason for an increased number of users attempting social media trends. Social media has been an important part of many people's life. To date, billions of people are registered to one or the other social media service and many of the users spend 120+ [1] minutes on social media. With an increase in social media users, many new trends and social media challenges are getting viral. Many users are actively taking part in one or other challenges. These challenges range for posting a picture with specific constraints to performing physical tasks [2, 3]. Many of the internet challenges have proven fatal and life-threatening to users, still, the trends have been continuing over the years with the change in its specificity. The users involved in the challenge range from celebrities to an average user. If the trend of many famous viral changes we observe, we can find the common thing that all the internet challenges involved either displaying physical strength or display of self in some of the other ways that grab the peer users' attention on the platform. This gives us the clue that beyond just trends, the neural pathway and mechanisms are involved in this. To understand first we focus on types of viral challenges and its classification. We classified
Research Paper
The International Journal of Indian Psychology
ISSN 2348-5396 (Online) | ISSN: 2349-3429 (Print)
Volume 8, Issue 2, April- June, 2020
DIP: 18.01.034/20200802, DOI: 10.25215/0802.034
http://www.ijip.in
© 2020, A Dhawan; licensee IJIP. This is an Open Access Research distributed under the terms of the Creative
Commons Attribution License (www.creativecommons.org/licenses/by/2.0), which permits unrestricted use,
distribution, and reproduction in any Medium, provided the original work is properly cited.
Psychological and neural basis of viral online internet challenges:
A review
Abhishek Dhawan
1
*
ABSTRACT
Psychology and human neural response are centrally associated with social media interaction.
An increase in social media use in recent years has been associated with an increase in the
number of internet viral trends. The number of internet challenges has been engaging millions
of people to take part in it. In this article, we are trying to focus on human behavior and its
neural basis of making internet trends viral. Dopaminergic pathways and one's social
dominance have been keen role players in this. The feedbacks and increased reaction on one's
uploaded post that sums up increased peer attention on social media can be linked with
dopamine pleasures and the reward cycle. Dopaminergic reinforcement triggers user tagging
multiple other users for taking up challenge. Challenges and trends involved displaying
physical fitness provides one with its increased social ranking as it can be traced with fittest
having advantages of social dominance within peers. Cortisol response may play an
important role in negative domain response. Hence activation of dopaminergic pathway and
benefit of elevated social ranking can be the reason for an increased number of users
attempting social media trends.
Keywords: Dopaminergic pathway, cortisol, Social dominance, Social media, Internet
Challenges.
Social media has been an important part of many people's life. To date, billions of people
are registered to one or the other social media service and many of the users spend 120+ [1]
minutes on social media. With an increase in social media users, many new trends and social
media challenges are getting viral. Many users are actively taking part in one or other
challenges. These challenges range for posting a picture with specific constraints to
performing physical tasks [2, 3]. Many of the internet challenges have proven fatal and life-
threatening to users, still, the trends have been continuing over the years with the change in
its specificity. The users involved in the challenge range from celebrities to an average user.
If the trend of many famous viral changes we observe, we can find the common thing that all
the internet challenges involved either displaying physical strength or display of self in some
of the other ways that grab the peer users' attention on the platform. This gives us the clue
that beyond just trends, the neural pathway and mechanisms are involved in this. To
understand first we focus on types of viral challenges and its classification. We classified
1
Consultant Scientist, Agricultural Development Trust, Baramati, Maharashtra, India
*Responding Author
Received: April 16, 2020; Revision Received: June 1, 2020; Accepted: June 25, 2020
Psychological and neural basis of viral online internet challenges: A review
© The International Journal of Indian Psychology, ISSN 2348-5396 (e)| ISSN: 2349-3429 (p) | 289
challenges in two types: Challenges involving physical task and Soft challenges, challenges
involving pictures, videos or creativity. To make analysis we classified 5 of the physical task
challenges and 4 in soft challenges.
Challenges involving physical task
This where the viral challenges that involved participants to perform the task that required
one or more of the physical skills including physical strength, pain bearing strength or
physical precession. The 5 challenges that went viral, we considered are as follows:
1. Cinnamon challenge: In 2013, this challenge involves swallowing a tablespoon of
cinnamon powder in timeframe of 60 seconds without liquid or water
2. Planking challenge: In 2013, holding a plank for maximum time as possible with
different variations.
3. Ice bucket challenge: This was stared in 2014, The Ice Bucket Challenge also known
as ALS Ice Bucket Challenge is an activity involving the dumping of a bucket full of
ice or ice water over a head.
4. Kylie Jenner lip challenge: In 2015, inserting lips into a shot glass, small jar or
bottle, and then sucking out the air which resulted in creating a vacuum.
5. Kick bottle opening: In year 2019, a bottle is placed on a table with its cap loosely
fixed on it. The person trying it out is required to untwist the cap with a roundhouse
kick.
Soft challenges
Challenges involving pictures, videos or creativity: This is the challenges that are consisting
of posting pictures, videos and such kind of self-representing contents with specific
conditions. The 4 challenges that went viral, we considered are as follows:
1. Mannequin challenge: 2016, In which people remain frozen in action like
mannequins while a moving camera film them
2. In my feelings challenge: 2018, It consisted of Jumping out of a moving vehicle and
dancing on the road on the music song by Drake's “In My Feelings”
3. 10 years photo challenge: 2019 Participants posted two images of their self-side by
side one of them which was taken at least ten years apart.
4. Sari challenge: 2020, Involved a female posting her photo in sari, traditional Indian
attire. This came to huge popularity in India.
Dopaminergic system
Dopaminergic systems [4] form the neural basis for a lot of people engaging in viral social
media challenges. Rewards can be defined as those objects or stimuli, which we will work to
acquire through the allocation of time, energy, or effort; that is, an object or goal that we
seek. Whenever we are exposed to a rewarding stimulus, the brain responds by increasing
the release of the neurotransmitter dopamine and thus giving the pleasurable feeling.
Dopamine and pleasurable feeling are important with respect to dopaminergic signaling as it
helps utilizing and allocation of energy [7]. Elevated Dopamine stimulates reinforcement
making users to do the same activity repeatedly. Dopamine [5] has a major role in reward
and pleasure systems. The dopaminergic system can be classified into four major pathways
[6]. Pathways are known as Mesolimbic Pathway, Mesocortical Pathway, Nigrostriatal
Pathway, and Tuberoinfundibular Pathway. Mesolimbic Pathway. Mesolimbic and
mesocortical systems play an important role in balancing reward versus cost estimates [7, 8].
The mesocortical pathway connects the ventral tegmentum to the prefrontal cortex. The
mesolimbic pathway connects the ventral tegmental area in the midbrain, to the ventral
striatum of the basal ganglia in the forebrain. The amygdala and hippocampus are key
Psychological and neural basis of viral online internet challenges: A review
© The International Journal of Indian Psychology, ISSN 2348-5396 (e)| ISSN: 2349-3429 (p) | 290
components of the limbic system and are associated with emotion and memory formation,
respectively.
Neural Basis of soft challenges
Social appreciation or social rewards tend to trigger the dopaminergic systems [12]. If we
look at the social challenges, there are two things we can consider that are 1. People are
getting an opportunity to show their best aspect of oneself for e.g.: beauty face, dancing
skills, creativity or good attires and 2. Showing the best aspect of self is generating positive
social rewards each time like, comment or reaction is received on the posted challenge post
that attributes to social appreciation. Social appreciation correlates to reward in this case
[13]. This reward triggers a dopaminergic system mostly mesolimbic pathway with giving
short term acute pleasurable feelings. Dopamine acts as a reinforcement factor. Elevated
levels of dopamine tend to make a person do the task repeatedly [14, 15]. This behavior
further promotes a user tagging multiple other users to take up the challenge. Social
motivation also triggers a competitive environment in neural aspects [16]. So when the peer
user of the same social level having bonding in positive or negative domain tags, this
motivates and triggers the competitive environment to take up the challenge. If the tag is
from the positive domain user [18] i.e. friends, serotonergic release can trigger the
competition and if the tag is from the negative domain user i.e. competitive or disliked,
cortisol release [17] can trigger the competition.
Neural Mechanisms involved in challenges having physical task
Here it’s not only the previously discussed dopaminergic systems have a major role but also
the evolutionary social dominance [20]. As per the mechanism of natural selection in
evolutionary theory, fittest always has the upper hand in survival [19]. To survive and
reproduce one needs higher social ranking or social dominance. Being fit physically than
comparative others increases the chance of social dominance. Also, in recent years, the trend
of dating online is increasing. Being fit and aesthetic increases the chance of getting a mate
Evolutionary and neurologically increased chances of getting mate increase the chance of
reproduction [21, 22, 23] and passing of genes to the next generation, supporting evolution.
The way to exhibit the alpha characteristics over the internet is to display strength,
endurance, pain bearing capacity, physical skills or body aesthetics through photos or
videos. Completing internet challenges involving physical task suffices both the
neurobiological and evolutionary motto. Completion of physical task says for e.g. planking
challenge not only peaks once fitness and social rank over the peer users but also increases
the chance of social dominance and increasing other gender attraction [22, 23]. So in these
kinds of challenges it is not only previously discussed neurobiology but also evolutionary
psychology comes into play.
Cortisol and Social Media
Most of the social media posts or internet challenges posts are the posts having positive end
results i.e. say for soft challenges faces in photos may be enhanced with filters, edits and
skills applied, etc. Not many posts with failed results or trolled comments are kept for a long
time. Many of the times posts having negative reactions are being deleted. Mostly but may
not be all times the challenges that don’t aim to provide good feedback or elevate your social
status are taken up or become viral. This is nothing but the type of social exclusion on the
internet. Intense encounters of social exclusion or relational dismissal can elicit cortisol
reactivity [10], especially when the assessment is unambiguous and remarkable. Social
rejection can likewise keep up raised cortisol levels in light of these dangers. According to a
study by Beekman JB et al [9], Post exclusion cortisol levels were significantly higher, and
Psychological and neural basis of viral online internet challenges: A review
© The International Journal of Indian Psychology, ISSN 2348-5396 (e)| ISSN: 2349-3429 (p) | 291
people reported greater perceived stress and negative affect. Also, Pre-Experience of Social
Exclusion affects the Hypothalamus-Pituitary-Adrenal Axis changing normal cortisol
response [11]. This can be an explanation of why some of the internet challenges do not get
viral.
DISCUSSION
Social media and its trends or online internet challenges may seem to be technological
advancement but underlying mechanisms tend to be neurological. Changes to dopamine
levels, modulate the response to viral internet challenges. The dopaminergic system plays
an important role in altering responses to social media activities. Social dominance, social
ranking and psychological motives of displaying strength can be the basis of many people
taking up physical tasks that become viral on the internet. The stress response generated by
cortisol alteration can result in trolling and some of the posts or internet challenges not
becoming viral. This conclusion needs to be asserted with further studies.
REFERENCES
1. How Much Time Do People Spend on Social Media in 2019? Marie Ennis-O'Connor
medium.com, Aug 8, 2019
2. The 7 Best Social Media ‘Challenges’ of All Time Dezmond Moore coiski.com,
November 15,2019
3. Social media challenges What went viral? sadia writtenbysadia.com, February 23,
2020
4. Hormones and the Social Brain Bruce S. McEwen Science Vol. 339, Issue 6117, pp.
279-280 DOI: 10.1126/science.1233713
5. Dopamine and reward: a view from the prefrontal cortex Chau, Bolton K.H; Jarvis,
Huw; Law, Chun-Kit; Chong, Trevor T.-J. Behavioural Pharmacology, Volume 29,
Number 7, October 2018, pp. 569-583(15)
6. Dopaminergic Neurons and Brain Reward Pathways: From Neurogenesis to Circuit
Assembly. Luo SX, Huang EJ. Am J Pathol. 2016;186(3):478488.
doi:10.1016/j.ajpath.2015.09.023
7. Putting desire on a budget: dopamine and energy expenditure, reconciling reward and
resources Beeler Jeff, Frazier Cristianne, Zhuang Xiaoxi Frontiers in Integrative
Neuroscience, Volume:6,2012 https://doi.org/10.3389/fnint.2012.00049
8. Neurobiologic processes in drug reward and addiction Adinoff B. Harv Rev
Psychiatry. 2004;12(6):305320 doi:10.1080/10673220490910844
9. Need to Belong, Not Rejection Sensitivity, Moderates Cortisol Response, Self-
Reported Stress, and Negative Affect Following Social Exclusion. Beekman JB,
Stock ML1, Marcus T J Soc Psychol. 2016;156(2):131-8 doi:
10.1080/00224545.2015.1071767
10. Cortisol Responses to Social Exclusion Sally S. Dickerson and Peggy M. Zoccola The
Oxford Handbook of Social Exclusion, Feb 2013
11. Effects of Pre-Experience of Social Exclusion on Hypothalamus-Pituitary-Adrenal
Axis and Catecholaminergic Responsiveness to Public Speaking Stress Weik U,
Kuepper Y, Hennig J, Deinzer R PLOS ONE 8(4): e60433
https://doi.org/10.1371/journal.pone.0060433
12. The rewarding nature of social interactions Krach S, Paulus FM, Bodden M, Kircher
T Front Behav Neurosci. 2010; 4:22 doi:10.3389/fnbeh.2010.00022
13. Baik Ja-Hyun Dopamine Signaling in reward-related behaviors Frontiers in Neural
Circuits, Volume:7, 013 doi=10.3389/fncir.2013.00152
Psychological and neural basis of viral online internet challenges: A review
© The International Journal of Indian Psychology, ISSN 2348-5396 (e)| ISSN: 2349-3429 (p) | 292
14. Role of brain dopamine in food reward and reinforcement. Wise RA. Philos Trans R
Soc Lond B Biol Sci. 2006;361(1471):11491158 doi:10.1098/rstb.2006.1854
15. Dopamine in Drug Abuse and Addiction: Results of Imaging Studies and Treatment
Implications Volkow ND, Fowler JS, Wang G, Swanson JM, Telang F Arch Neurol.
2007;64(11):15751579 doi:10.1001/archneur.64.11.1575
16. A specific role for serotonin in overcoming effort cost Meyniel F, Goodwin GM,
Deakin JW, et al Elife. 2016;5:e17282 doi:10.7554/eLife.17282
17. Hormones and Behavior Kathleen V.Casto & David A.Edwards Volume 82, June
2016, Pages 21-37 https://doi.org/10.1016/j.yhbeh.2016.04.004
18. Opponency revisited: competition and cooperation between dopamine and serotonin
Boureau YL, Dayan P. Neuropsychopharmacology. 2011;36(1):7497
19. From ‘natural selection’ to ‘survival of the fittest’: On the significance of Spencer’s
refashioning of Darwin in the 1860s Offer, J. (2014). Journal of Classical Sociology,
14(2), 156177 https://doi.org/10.1177/1468795X13491646
20. The Evolution of Interacting Phenotypes: Genetics and Evolution of Social
Dominance. Allen J. Moore, Kenneth F. Haynes, Richard F. Preziosi, and Patricia J.
Moore The American Naturalist 2002 160: S6, S186-S197
21. Kleshchev, M.A., Osadchuk, L.V. Social domination and reproductive success in
male laboratory mice (Mus musculus). J Evol Biochem Phys 50, 227233 (2014)
https://doi.org/10.1134/S0022093014030053
22. Social Dominance and Courtship and Mating Behaviour in Rams in Non‐Competitive
and Competitive Pen Tests R Ungerfeld, SP González‐Pensado Reproduction in
Domestic Animals https://doi.org/10.1111/j.1439-0531.2007.00987
23. The inheritance of social dominance, mating behaviour and attractiveness to mates in
male Nauphoeta cinerea Author links open overlay panelAllen J.Moore Animal
Behaviour Volume 39, Issue 2, February 1990, Pages 388-397
24. Detection of Dopamine Dynamics in the Brain R. Mark WightmanLeslie J.
MayAdrian C. Michael Anal. Chem. 1988, 60, 13, 769A-793A
25. The role of dopamine in reward and pleasure behaviour review of data from
preclinical research R. A. Bressan et al Acta Psychiatrica Scandinavica: 05 May 2005
https://doi.org/10.1111/j.1600-0447.2005.00540.x
26. Journal home page for Trends in Neurosciences, Trends in Neurosciences, Volume 3,
Issue 4, April 1980, Pages 91-95 The dopamine synapse and the notion of ‘pleasure
centers’ in the brain Roy A.Wise https://doi.org/10.1016/0166-2236(80)90035-1
27. What is the role of dopamine in reward: hedonic impact, reward learning, or incentive
salience? Kent CBerridge, Terry ERobinson Brain Research Reviews, Volume 28,
Issue 3, December 1998, Pages 309-369 https://doi.org/10.1016/S0165-
0173(98)00019-8
28. Pharmacology and behavioral pharmacology of the mesocortical dopamine system
T.M.Tzschentke Progress in Neurobiology, Volume 63, Issue 3, February 2001, Pages
241-320 https://doi.org/10.1016/S0301-0082(00)00033-2
29. Opinion, Social dominance and stress hormones ScottCreel Trends in Ecology &
Evolution, Volume 16, Issue 9, 1 September 2001, Pages 491-497
https://doi.org/10.1016/S0169-5347(01)02227-3
30. The concept of social dominance Thelma E.Rowell Behavioral Biology,Volume 11,
Issue 2, June 1974, Pages 131-154 https://doi.org/10.1016/S0091-6773(74)90289-2
Psychological and neural basis of viral online internet challenges: A review
© The International Journal of Indian Psychology, ISSN 2348-5396 (e)| ISSN: 2349-3429 (p) | 293
Acknowledgements
The author appreciates all those who participated in the study and helped to facilitate the
research process.
Conflict of Interest
The author declared no conflict of interest.
How to cite this article: A Dhawan (2020). Psychological and neural basis of viral online
internet challenges: A review. International Journal of Indian Psychology, 8(2), 288-293.
DIP:18.01.034/20200802, DOI:10.25215/0802.034
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