People's perception of time is subjective and based not only on their emotional state but also on heartbeat and heart rate (HR), two new studies suggest.
Researchers studied young adults with an electrocardiogram (ECG), measuring electrical activity at millisecond resolution while participants listened to tones that varied in duration. Participants were asked to report whether certain tones were longer or shorter, in relation to others.
The researchers found that the momentary perception of time was not continuous but rather expanded or contracted with each heartbeat. When the heartbeat preceding a tone was shorter, participants regarded the tone as longer in duration; but when the preceding heartbeat was longer, the participants experienced the tone as shorter.
"Our findings suggest that there is a unique role that cardiac dynamics play in the momentary experience of time," lead author Saeedah Sadeghi, MSc, a doctoral candidate in the department of psychology at Cornell University, Ithaca, New York, told theheart.org | Medscape Cardiology.
The study was published online March 2 in Psychophysiology.
In a second study, published the following day in the journal Current Biology, a separate team of researchers asked participants to judge whether a brief event — the presentation of a tone or an image — was shorter or longer than a reference duration. ECG was used to track systole and diastole when participants were presented with these events.
The researchers found that the durations were underestimated during systole and overestimated during diastole, suggesting that time seemed to "speed up" or "slow down," based on cardiac contraction and relaxation. When participants rated the events as more arousing, their perceived durations contracted, even during diastole.
"In our new paper, we show that our heart shapes the perceived duration of events, so time passes quicker when the heart contracts but slower when the heart relaxes," lead author Irena Arslanova, PhD, postdoctoral researcher in cognitive neuroscience, Royal Holloway University of London, UK, told theheart.org | Medscape Cardiology.
"Subjective time is malleable," observe Sadeghi and colleagues in their publication. "Rather than being a uniform dimension, perceived duration has 'wrinkles,' with certain intervals appearing to dilate or contract relative to objective time" — a phenomenon sometimes referred to as "distortion."
"We have known that people aren't always consistent in how they perceive time, and objective duration doesn't always explain subjective perception of time," Sadeghi said.
Although the potential role of the heart in the experience of time has been hypothesized, research into the heart-time connection has been limited, with previous studies focusing primarily on estimating the average cardiac measures on longer time scales over seconds to minutes.
The current study sought to investigate "the beat-by-beat fluctuations of the heart period on the experience of brief moments in time" because, compared with longer time scales, subsecond temporal perception "has different underlying mechanisms" and a subsecond stimulus can be a "small fraction of a heartbeat."
To home in on this small fraction, the researchers studied 45 participants (ages 18-21), who listened to 210 tones ranging in duration from 80 ms (short) to 188 ms (long). The tones were linearly spaced at 18-ms increments (80, 98, 116, 134, 152, 170, 188).
Participants were asked to categorize each tone as "short" or "long." All tones were randomly assigned to be synchronized either with the systolic or diastolic phase of the cardiac cycle (50% each). The tones were triggered by participants' heartbeats.
In addition, participants engaged in a heartbeat-counting activity, in which they were asked not to touch their pulse but to count their heartbeats by tuning in to their bodily sensations at intervals of 25, 35, and 45 seconds.
"Participants exhibited an increased heart period after tone onset, which returned to baseline following an average canonical bell shape," the authors report.
The researchers performed regression analyses to determine how, on average, the heart rate before the tone was related to perceived duration or how the amount of change after the tone was related to perceived duration.
They found that when the heart rate was higher before the tone, participants tended to be more accurate in their time perception. And when the heartbeat preceding a tone was shorter, participants experienced the tone as longer; conversely, when the heartbeat was longer, they experienced the duration of the identical sound as shorter.
When participants focused their attention on the sounds, their heart rate was affected such that their orienting responses actually changed their heart rate and, in turn, their temporal perception.
"The orienting response is classical," Sadeghi commented. "When you attend to something unpredictable or novel, the act of orienting attention decreases the HR."
She explained that the heartbeats are "noise to the brain." When people need to perceive external events, "a decrease in HR facilitates the intake of things from outside and facilitates sensory intake."
A lower HR "makes it easier for the person to take in the tone and perceive it, so it feels as though they perceive more of the tone and the duration seems longer — similarly, when the HR decreases."
It is unknown whether this is a causal relationship, she cautioned, "but it seems as though the decrease in HR somehow makes it easier to 'get' more of the tone, which then appears to have longer duration."
"We know that experienced time can be distorted," said Arslanova. "Time flies by when we’re busy or having fun but drags on when we're bored or waiting for something, yet we still don't know how the brain gives rise to such elastic experience of time."
The brain controls the heart in response to the information the heart provides about the state of the body, she noted, "but we have begun to see more research showing that the heart–brain relationship is bidirectional."
This means that the heart plays a role in shaping "how we process information and experience emotions." In this analysis, Arslanova and colleagues "wanted to study whether the heart also shapes the experience of time."
To do so, they conducted two experiments.
In the first, participants (n = 28) were presented with brief events during systole or during diastole. The events took the form of an emotionally neutral visual shape or auditory tone, shown for durations of 200 to 400 ms.
Participants were asked whether these events were of longer or shorter duration, compared to a reference duration.
The researchers found significant main effect of cardiac phase systole (F(1,27) = 8.1, P =.01), with stimuli presented at diastole regarded, on average, as 7 ms longer than those presented at systole.
They also found a significant main effect of modality (F(1,27) = 5.7, P = .02), with tones judged, on average, as 13 ms longer than visual stimuli.
"This means that time 'sped up' during the heart's contraction and 'slowed down' during the heart's relaxation," Arslanova commented.
The effect of cardiac phase on duration perception was independent of changes in HR, the authors note.
In the second experiment, participants performed a similar task, but this time, it involved the images of faces containing emotional expressions. The researchers again observed a similar pattern of time appearing to speed up during systole and slow down during diastole, with stimuli present at diastole regarded as being an average 9 ms longer than those presented at systole.
These opposing effects of systole and diastole on time perception were present only for low and average arousal ratings (b = 14.4 [SE 3.2], P < .001 and b = 9.2 [2.3], P <.001, respectively). However, this effect disappeared when arousal ratings increased (b = 4.1 [3.2] P =.21).
"Interestingly, when participants rated the events as more arousing, their perceived durations contracted, even during the heart's relaxation," Arslanova observed. "This means that in a non-aroused state, the two cardiac phases pull the experienced duration in opposite directions — time contracts, then expands."
The findings "also predict that increasing HR would speed up passing time, making events seem shorter, because there will be a stronger influence from the heart's contractions," she said.
She described the relationship between time perception and emotion as complex, noting that the findings are important because they show "that the way we experience time cannot be examined in isolation from our body," she said.
Commenting for theheart.org | Medscape Cardiology, Martin Wiener, PhD, assistant professor, George Mason University, Fairfax, Virginia, said both papers "provide converging evidence on the role of the heart in our perception of time."
Together, "the results share that our sense of time — that is, our incoming sensory perception of the present 'moment' — is adjusted or 'gated' by both our HR and cardiac phase," said Wiener, who is also the executive director of the Timing Research Forum.
The studies "provide a link between the body and the brain, in terms of our perception, and that we cannot study one without the context of the other," said Wiener, who was not involved with the current study.
"All of this opens up a new avenue of research, and so it is very exciting to see," Wiener stated.
No source of funding was listed for the study by Sadeghi et al. Sadeghi and co-authors declare no relevant financial relationships.
Arslanova and co-authors declare no competing interests. Senior author Manos Tsakiris, PhD, receives funding from the European Research Council Consolidator Grant. Wiener declares no relevant financial relationships.
Psychophysiology. Published online March 2, 2023. Full text
Curr Biol. Published online Mach 3, 2023. Full text
Batya Swift Yasgur MA, LSW is a freelance writer with a counseling practice in Teaneck, NJ. She is a regular contributor to numerous medical publications, including Medscape and WebMD, and is the author of several consumer-oriented health books as well as Behind the Burqa: Our Lives in Afghanistan and How We Escaped to Freedom (the memoir of two brave Afghan sisters who told her their story).
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Cite this: Heart Rate, Cardiac Phase Influence Perception of Time - Medscape - Mar 31, 2023.