The heart has held a central place in theories of human function for centuries. It was proclaimed as the seat of life in Ancient Greek and Byzantine medical literature, and the Ancient Egyptians embalmed their dead by carefully preserving the heart while unceremoniously discarding the brain1. This stands as a stark inversion of today’s physiological priorities. However, researchers have recently again been investigating human cognition and behaviour from the perspective of cardiac physiology.
My colleagues and I recently published a paper showing that temporal reproduction is associated with heart rate. In this post I will briefly discuss this paper, and review the literature on why heart rate — and autonomic nervous system function in general — is deeply connected to cognition.
The idea that periodic physiological signals might constitute a biological clock is not new2. The most popular, recent account of this idea, endorsed by Marc Wittmann and Bud Craig, suggests that time perception is a function of integrated interoceptive signals34, which explains why physiological factors such as arousal5 and body temperature6 can affect time perception.
However, a simple linear relationship between heart rate and time perception is almost definitely an oversimplification. For instance, it’s clear that increasing heart rate (by exercise for instance) doesn’t affect time perception significantly7. But there are other elements of cardiac signals that provide a wider overview of the autonomic nervous system. This arises because the heart is innervated by both the sympathetic (SNS) and parasympathetic nervous system (PNS), and each of these arms have slightly different latencies (the PNS acts more rapidly on the heart). Thus, different components of the variability of heart rate can be attributed to the SNS and PNS. This means, for instance, that if analysed in the time-frequency domain, power in the high-frequency band of heart rate variability reflects the functioning of the PNS8.
Over the last decade or so, researchers have used these types of analysis techniques to link cardiac signals with different types of cognitive processes. This includes emotion regulation9, self-control10, and working memory11. Further to this, directly stimulating the ANS via the vagus nerve can also enhance memory processes12.
Temporal reproduction and heart rate variability
In our study, we assessed whether performance in a temporal reproduction task was associated with these different measures of cardiac activity. Healthy participants completed a standard temporal reproduction task with durations spanning from 2 – 15 seconds, while we recorded electrocardiogram (ECG). We characterised participants temporal reproductions with a two parameter psychophysical function (Steven’s power law), where the exponent parameter indicates the concavity of the function and thus whether participants tend to under-reproduce (exponent > 1), or over-reproduce (exponent < 1) intervals.
We found that that different frequency components of heart rate variability were associated with differences in participants’ reproductions. Specifically, we found that the high-frequency component was negatively associated with the exponent parameter of the psychophysical function. This suggests that individuals with higher PNS cardiac influence under-reproduced longer intervals compared with those with lower PNS cardiac influence. We also found a similar negative association between the low-frequency component and the exponent. The interpretation of the low-frequency component of heart rate variability is not as clear as that of the high-frequency component, as it reflects physiological processes other than purely SNS function13. However, increases in the low-frequency component have been previously been associated with decreases in attention and fatigue due to time-on-task14, thus it is possible that individuals who experienced more task-related fatigue performed more poorly on the reproduction task. Overall, these results show that time perception is associated with autonomic nervous system function.
This is not the first time that researchers have found links between time perception and heart rate. For instance, one study found that individuals have better absolute accuracy at reproducing durations when their heart rate slows down during the encoding of the sample interval15. Individuals with higher resting heart rate variability are also more accurate at reproducing durations16. Similarly, individuals with overall higher heart rate variability are also more accurate in a temporal bisection task17. As the PNS is responsible for slowing down heart rate, and is also the principle determinant of heart rate variability, this would suggest that individuals with higher PNS function are more accurate at duration reproduction in general.
However, other studies that have directly stimulated the vagus nerve (the main nerve of the PNS), have found that this can cause overestimations (under-reproductions) of time in the ranges of 34 – 230 seconds18. This is approximately consistent with our results showing that individuals with higher PNS function under-reproduced durations, however it conflicts somewhat with the results of the above studies. One possible discrepancy is that the above studies used absolute measures of accuracy, whereas we observed a directional effect. Whatever the reason for these differences, the relationship between autonomic nervous system function and temporal reproduction clearly merits further investigation.
In sum, this research seems to suggest that while the beats of the heart themselves are not analogous to a pacemaker, changes in the autonomic nervous system are either a corollary of a timing mechanism, or the autonomic nervous system directly plays role in how humans perceive time. Given the non-invasive nature of heart rate recordings, future research may be able to clarify exactly how signals from the heart inform our perception of time.
Fung, B. J., Crone, D. L., Bode, S., & Murawski, C. (2017). Cardiac Signals Are Independently Associated with Temporal Discounting and Time Perception. Frontiers in Behavioral Neuroscience, 11, 369. http://doi.org/10.3389/fnbeh.2017.00001
More reading on how cardiac signals relate to cognition:
Thayer, J. F., & Lane, R. D. (2000). A model of neurovisceral integration in emotion regulation and dysregulation. Journal of Affective Disorders, 61(3), 201–216. http://doi.org/10.1016/S0165-0327(00)00338-4
Thayer, J. F., & Lane, R. D. (2009). Claude Bernard and the heart–brain connection: Further elaboration of a model of neurovisceral integration. Neuroscience and Biobehavioral Reviews, 33(2), 81–88. http://doi.org/10.1016/j.neubiorev.2008.08.004
- Lykouras, E., Poulakou-Rebelakou, E., & Ploumpidis, D. N. (2010). Searching the seat of the soul in Ancient Greek and Byzantine medical literature. Acta Cardiologica, 65(6), 619–626. http://doi.org/10.2143/AC.65.6.2059857 ↩︎
- Goudriaan, J.C., 1921. Le rhythm psychique dans ses rapports avec les frequences cardiaques et respiratoires. Arch. Neerl. Physiol. 6, 77–110. ↩︎
- Craig, A. D. (2009). Emotional moments across time: a possible neural basis for time perception in the anterior insula. Philosophical Transactions of the Royal Society B-Biological Sciences, 364(1525), 1933–1942. http://doi.org/10.1098/rstb.2009.0008 ↩︎
- Wittmann, M. (2009). The inner experience of time. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 364(1525), 1955–1967. http://doi.org/10.1098/rstb.2009.0003 ↩︎
- Droit-Volet, S., & Meck, W. H. (2007). How emotions colour our perception of time. Trends in Cognitive Sciences, 11(12), 504–513. http://doi.org/10.1016/j.tics.2007.09.008 ↩︎
- Wearden, J. H., & Penton-Voak, I. S. (1995). Feeling the heat: Body temperature and the rate of subjective time, revisited. The Quarterly Journal of Experimental Psychology, 48(2), 129–141. http://doi.org/10.1080/14640749508401443 ↩︎
- Schwarz, M. A., Winkler, I., & Sedlmeier, P. (2012). The heart beat does not make us tick: The impacts of heart rate and arousal on time perception. Attention, Perception & Psychophysics, 75(1), 182–193. http://doi.org/10.3758/s13414-012-0387-8 ↩︎
- Berntson, G. G., Bigger, J. T., Eckberg, D. L., Grossman, P., Kaufmann, P. G., Malik, M., et al. (1997). Heart rate variability: origins, methods, and interpretive caveats. Psychophysiology, 34(6), 623–648. ↩︎
- Park, G., & Thayer, J. F. (2014). From the heart to the mind: cardiac vagal tone modulates top-down and bottom-up visual perception and attention to emotional stimuli. Frontiers in Psychology, 5, 278. http://doi.org/10.3389/fpsyg.2014.00278 ↩︎
- Segerstrom, S. C., & Nes, L. S. (2007). Heart Rate Variability Reflects Self-Regulatory Strength, Effort, and Fatigue. Psychological Science, 18(3), 275–281. http://doi.org/10.1111/j.1467-9280.2007.01888.x ↩︎
- Hansen, A. L., Johnsen, B. H., & Thayer, J. F. (2003). Vagal influence on working memory and attention. International Journal of Psychophysiology, 48(3), 263–274. http://doi.org/10.1016/S0167-8760(03)00073-4 ↩︎
- Clark, K. B., Naritoku, D. K., Smith, D. C., Browning, R. A., & Jensen, R. A. (1999). Enhanced recognition memory following vagus nerve stimulation in human subjects. Nature Neuroscience, 2(1), 94–98. http://doi.org/10.1038/4600 ↩︎
- Reyes Del Paso, G. A., Langewitz, W., Mulder, L. J. M., van Roon, A., & Duschek, S. (2013). The utility of low frequency heart rate variability as an index of sympathetic cardiac tone: A review with emphasis on a reanalysis of previous studies. Psychophysiology, 50(5), 477–487. http://doi.org/10.1111/psyp.12027 ↩︎
- Fairclough, S. H., & Houston, K. (2004). A metabolic measure of mental effort. Biological Psychology, 66(2), 177–190. http://doi.org/10.1016/j.biopsycho.2003.10.001 ↩︎
- Meissner, K., & Wittmann, M. (2011). Body signals, cardiac awareness, and the perception of time. Biological Psychology, 86(3), 289–297. http://doi.org/10.1016/j.biopsycho.2011.01.001 ↩︎
- Pollatos, O., Laubrock, J., & Wittmann, M. (2014). Interoceptive Focus Shapes the Experience of Time. PloS One, 9(1), e86934. http://doi.org/10.1371/journal.pone.0086934 ↩︎
- Cellini, N., Mioni, G., Levorato, I., Grondin, S., Stablum, F., & Sarlo, M. (2015). Heart rate variability helps tracking time more accurately. Brain and Cognition, 101, 57–63. http://doi.org/10.1016/j.bandc.2015.10.003 ↩︎
- Biermann, T., Kreil, S., Groemer, T. W., Maihöfner, C., Richter-Schmiedinger, T., Kornhuber, J., & Sperling, W. (2011). Time Perception in Patients with Major Depressive Disorder during Vagus Nerve Stimulation. Pharmacopsychiatry, 44(05), 179–182. http://doi.org/10.1055/s-0031-1280815 ↩︎