Sociodian Rhythm: Eye Contact and the Neurobiology of Social Synchronization
Main Article Content
Abstract
Background: Circadian rhythms regulate physiological processes in alignment with environmental light cycles. However, humans—particularly as highly social organisms—demonstrate behavioral and physiological adaptations that follow socially derived cues. This paper introduces the concept of sociodian rhythm, a social counterpart to circadian regulation, and proposes that social entrainment, particularly via eye contact, may serve as a dominant synchronizing mechanism.
Objective: To examine the theoretical basis, biological substrates, and evolutionary implications of sociodian rhythm, with a focus on how eye contact and social cues regulate behavioral and physiological synchrony in humans.
Methods: This review integrates findings from neuroscience, behavioral studies, chronobiology, and ethology to evaluate the interplay between social cues, circadian mechanisms, and eye-mediated neuroregulation. Comparative animal studies, neuroendocrine pathways, and psychophysiological models are also explored.
Results: Social cues—including gaze, pupillary mimicry, and oxytocin release—modulate internal timing systems via pathways involving the suprachiasmatic nucleus (SCN), lateral habenula (LHb), and nucleus accumbens. Eye contact acts as a rapid entrainment mechanism, facilitating alignment in arousal, emotional state, and partnership readiness. Sociodian rhythms may override or restructure circadian rhythms under socially dense conditions.
Conclusion: Sociodian rhythm emerges as a fundamental mechanism for collective behavior and group cohesion. Its regulation through eye contact and oxytocin-mediated synchrony suggests a neurobiological foundation for social timing that complements, and in some cases surpasses, light-based circadian entrainment.
Keywords:
Sociodian rhythm, circadian synchronization, social entrainment, eye contact, pupillary mimicry, oxytocin, suprachiasmatic nucleus, social rhythm theory, lateral habenula, social neurobiology
Article Details
How to Cite
ÜNSALVER, Barış Önen; CEYLAN, Mehmet Emin.
Sociodian Rhythm: Eye Contact and the Neurobiology of Social Synchronization.
Medical Research Archives, [S.l.], v. 13, n. 10, oct. 2025.
ISSN 2375-1924.
Available at: <https://esmed.org/MRA/mra/article/view/6978>. Date accessed: 05 dec. 2025.
doi: https://doi.org/10.18103/mra.v13i10.6978.
Section
Review Articles
The Medical Research Archives grants authors the right to publish and reproduce the unrevised contribution in whole or in part at any time and in any form for any scholarly non-commercial purpose with the condition that all publications of the contribution include a full citation to the journal as published by the Medical Research Archives.
References
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40. Hu H, Cui Y, Yang Y. Circuits and functions of the lateral habenula in health and in disease. Nat Rev Neurosci. 2020;21(5):277–295. doi:10.1038/ s41583-020-0281-3
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42. Zhou L, Li F, Xu HB, et al. Inhibition of the lateral habenula improves depressive-like behavior in rats with chronic neuropathic pain. Neurosci Lett. 2017;653:30–35. doi:10.1016/j.neulet.2017.05.013
43. Baño-Otálora B, Piggins HD. Contributions of the lateral habenula to circadian timekeeping. Philos Trans R Soc Lond B Biol Sci. 2017;372(1734): 20160258. doi:10.1098/rstb.2016.0258
44. Hattar S, Kumar M, Park A, et al. Central projections of melanopsin-expressing retinal ganglion cells in the mouse. J Comp Neurol. 2006; 497(3):326–349. doi:10.1002/cne.20970
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46. Laeng B, Sirois S, Gredebäck G. Pupillometry: A window to the preconscious? Perspect Psychol Sci. 2012;7(1):18–27. doi:10.1177/1745691611427305
47. Frank E. Two-year outcomes for interpersonal and social rhythm therapy in individuals with bipolar I disorder. Arch Gen Psychiatry. 2005;62 (9):996–1004.
48. Zheng S, Liang Z, Qu Y, et al. Kuramoto Model-Based Analysis Reveals Oxytocin Effects on Brain Network Dynamics. Int J Neural Syst. 2022;32 (2):2250002. doi:10.1142/S0129065722500022
49. Auyeung B, Lombardo MV, Heinrichs M, et al. Oxytocin increases eye contact during a real-time, naturalistic social interaction in males with and without autism. Transl Psychiatry. 2015;5(2):e507. Published 2015 Feb 10. doi:10.1038/tp.2014.146
50. Mistlberger RE, Skene DJ. Social influences on mammalian circadian rhythms: Animal and human studies. Biol Rev. 2004;79(3):533–556.
2. Siehler O, Wang S, Bloch G. Social synchronization of circadian rhythms with a focus on honeybees. Philos Trans R Soc Lond B Biol Sci. 2021;376(1835): 20200342. doi:10.1098/rstb.2020.0342
3. Roenneberg T, Allebrandt KV, Merrow M, Vetter C. Social jetlag and obesity. Curr Biol. 2012; 22(10):939–943.
4. Grandin LD, Alloy LB, Abramson LY. The social zeitgeber theory, circadian rhythms, and mood disorders: review and evaluation. Clin Psychol Rev. 2006;26(6):679-694. doi:10.1016/j.cpr.2006.07.001
5. Ehlers CL, Frank E, Kupfer DJ. Social zeitgebers and biological rhythms: A unified approach to understanding the etiology of depression. Arch Gen Psychiatry. 1988;45:948–952.
6. Wittmann M, Dinich J, Merrow M, Roenneberg T. Social jetlag: Misalignment of biological and social time. Chronobiol Int. 2006;23(1-2):497–509.
7. Levandovski R, Dantas G, Caumo W, et al. Depression scores associate with chronotype and social jetlag in a rural population. Chronobiol Int. 2011;28(9):771–778.
8. Samson DR, Crittenden AN, Mabulla IA, et al. Chronotype variation drives night-time sentinel-like behaviour in hunter-gatherers. Proc Biol Sci. 2017;284(1858):20170967.
9. Fuchikawa T, Eban-Rothschild A, Nagari M, et al. Potent social synchronization can override photic entrainment of circadian rhythms. Nat Commun. 2016;7:11662.
10. Kramer A, Yang FC, Snodgrass SR, et al. Regulation of daily locomotor activity and sleep in mice depends on nonphotic entrainment. J Biol Rhythms. 2001;16(5):400–411.
11. Blume C, Schmidt MH, Cajochen C. Effects of the COVID-19 lockdown on human sleep and rest–activity rhythms. Curr Biol. 2020;30(14):R795–R797.
12. Huang Y, Zhao N. Generalized anxiety disorder, depressive symptoms and sleep quality during COVID-19 epidemic in China: A web-based cross-sectional survey. Psychiatry Res. 2020;288:112954.
13. Umberson D, Montez JK. Social relationships and health: A flashpoint for health policy. J Health Soc Behav. 2010;51(Suppl):S54–S66.
14. Cermakian N, Boivin DB. The regulation of central and peripheral circadian clocks in humans. Obes Rev. 2009;10(s2):25–36. doi:10.1111/j.1467-789X.2009.00698.x
15. Winfree AT. The Geometry of Biological Time. 2nd ed. Springer; 2001.
16. Glass L, Mackey MC. From Clocks to Chaos: The Rhythms of Life. Princeton University Press; 1988.
17. Karatsoreos IN, Bhagat S, Bloss EB, et al. Disruption of circadian clocks has ramifications for metabolism, brain, and behavior. Proc Natl Acad Sci U S A. 2011;108(4):1657–1662.
18. Levine JD, Funes P, Dowse HB, Hall JC. Resetting the circadian clock by social experience in Drosophila melanogaster. Science. 2002;298(56 00):2010-2012. doi:10.1126/science.1076008
19. Sakai T, Ishida N. Circadian rhythms of female mating activity governed by clock genes in Drosophila. Proc Natl Acad Sci U S A. 2001;98(16): 9221–9225.
20. Liang X, Holy TE, Taghert PH. Homeostatic and circadian modulation of social behavior in mice. Nat Commun. 2022;13:4823.
21. Aschoff J, Wever R. Spontanperiodik des Menschen bei Ausschluß aller Zeitgeber. Naturwissenschaften. 1962;49(7):337–342.
22. Weissová K, Bartošová K, Sládek M, Sumová A. Svalbard: The challenges of monitoring circadian rhythms in the high Arctic. Physiol Behav. 2019; 198:72–76.
23. Zhao H, Rusak B, Zhang M. Circadian regulation of midbrain dopaminergic neurons and behavioral consequences. Sleep Med. 2015;16(7):763–770.
24. Leong V, Byrne E, Clackson K, et al. Speaker gaze increases information coupling between infant and adult brains. Proc Natl Acad Sci U S A. 2017;114(50):13290–13295.
25. Farroni T, Csibra G, Simion F, Johnson MH. Eye contact detection in humans from birth. Proc Natl Acad Sci U S A. 2002;99(14):9602–9605.
26. Feldman R. Parent–infant synchrony and the construction of shared timing: Physiological precursors, developmental outcomes, and risk conditions. J Child Psychol Psychiatry. 2007;48(3-4):329–354.
27. Feldman R. Parenting behavior as the environment where children grow. In: Mayes LC, Lewis M, eds. The Cambridge Handbook of Environment in Human Development. Cambridge University Press; 2012:535–567.
28. Kobayashi H, Kohshima S. Unique morphology of the human eye. Nature. 2001;409(6826):171.
29. Senju A, Johnson MH. The eye contact effect: Mechanisms and development. Trends Cogn Sci. 2009;13(3):127–134.
30. Harrison NA, Singer T, Rotshtein P, et al. Pupillary contagion: Central mechanisms engaged in sadness processing. Soc Cogn Affect Neurosci. 2006;1(1):5–17.
31. Demos KE, Kelley WM, Ryan SL, et al. Human amygdala sensitivity to the pupil size of others. Cereb Cortex. 2008;18(12):2729–2734.
32. Kleinke CL. Gaze and eye contact: A research review. Psychol Bull. 1986;100(1):78–100.
33. Adolphs R, Tranel D, Damasio AR. Impaired recognition of emotion in facial expressions following bilateral damage to the human amygdala. Nature. 1994;372(6507):669–672.
34. Guastella AJ, Mitchell PB, Dadds MR. Oxytocin increases gaze to the eye region of human faces. Biol Psychiatry. 2008;63(1):3–5.
35. Riem MM, van IJzendoorn MH, Tops M, et al. No laughing matter: Intranasal oxytocin administration changes functional brain connectivity during exposure to infant laughter. Neuropsychopharmacology. 2011;36(6):1257–1265.
36. Kret ME, De Dreu CK. Pupil-mimicry conditions trust in partners: Moderation by oxytocin and group membership. Proc R Soc Lond B Biol Sci. 2017;284(1859):20162554.
37. Feldman R, Gordon I, Schneiderman I, et al. Natural variations in maternal and paternal care are associated with systematic changes in oxytocin following parent–infant contact. Psychoneuroendocrinology. 2010;35(8):1133–1141.
38. Hattar S, Liao HW, Takao M, et al. Melanopsin-containing retinal ganglion cells: Architecture, projections, and intrinsic photosensitivity. J Neurosci. 2006;26 (47):12561–12571.
39. Proulx CD, Hikosaka O, Malinow R. Reward processing by the lateral habenula in normal and depressive behaviors. Nat Neurosci. 2014;17(9): 1146–1152. doi:10.1038/nn.3779
40. Hu H, Cui Y, Yang Y. Circuits and functions of the lateral habenula in health and in disease. Nat Rev Neurosci. 2020;21(5):277–295. doi:10.1038/ s41583-020-0281-3
41. Lecca S, Meye FJ, Mameli M. The lateral habenula in addiction and depression: An anatomical, synaptic and behavioral overview. Eur J Neurosci. 2014;39(7):1170–1178. doi:10.1111/ejn.12480
42. Zhou L, Li F, Xu HB, et al. Inhibition of the lateral habenula improves depressive-like behavior in rats with chronic neuropathic pain. Neurosci Lett. 2017;653:30–35. doi:10.1016/j.neulet.2017.05.013
43. Baño-Otálora B, Piggins HD. Contributions of the lateral habenula to circadian timekeeping. Philos Trans R Soc Lond B Biol Sci. 2017;372(1734): 20160258. doi:10.1098/rstb.2016.0258
44. Hattar S, Kumar M, Park A, et al. Central projections of melanopsin-expressing retinal ganglion cells in the mouse. J Comp Neurol. 2006; 497(3):326–349. doi:10.1002/cne.20970
45. Mitre M, Marlin BJ, Schiavo JK, et al. A Distributed Network for Social Cognition Enriched for Oxytocin Receptors. J Neurosci. 2016;36(8):251 7-2535. doi:10.1523/JNEUROSCI.2409-15.2016
46. Laeng B, Sirois S, Gredebäck G. Pupillometry: A window to the preconscious? Perspect Psychol Sci. 2012;7(1):18–27. doi:10.1177/1745691611427305
47. Frank E. Two-year outcomes for interpersonal and social rhythm therapy in individuals with bipolar I disorder. Arch Gen Psychiatry. 2005;62 (9):996–1004.
48. Zheng S, Liang Z, Qu Y, et al. Kuramoto Model-Based Analysis Reveals Oxytocin Effects on Brain Network Dynamics. Int J Neural Syst. 2022;32 (2):2250002. doi:10.1142/S0129065722500022
49. Auyeung B, Lombardo MV, Heinrichs M, et al. Oxytocin increases eye contact during a real-time, naturalistic social interaction in males with and without autism. Transl Psychiatry. 2015;5(2):e507. Published 2015 Feb 10. doi:10.1038/tp.2014.146
50. Mistlberger RE, Skene DJ. Social influences on mammalian circadian rhythms: Animal and human studies. Biol Rev. 2004;79(3):533–556.