Cardiac signals reflect the function of the autonomic nervous system and have previously been associated with a range of self-regulatory behaviours such as emotion regulation and memory recall. It is unknown whether cardiac signals may also be associated with self-regulation in the temporal domain, in particular impulsivity. We assessed both decision impulsivity (temporal discounting) and time perception impulsivity (duration reproduction) in 120 participants while they underwent electrocardiography in order to test whether cardiac signals were related to these two aspects of impulsivity. We found that over the entire period of task performance, individuals with higher heart rates had a tendency toward lower discount rates, supporting previous research that has associated sympathetic responses with decreased impulsivity. We also found that low-frequency components of heart rate variability were associated with a less accurate perception of time, suggesting that time perception may be modulated by autonomic nervous system function. Overall, these findings constitute preliminary evidence that autonomic function plays an important role in both decision impulsivity and time perception.

/pdf/cardiac-signals-are-independently-associated-with-temporal-2x291rlaz2.pdf

Cardiac Signals Are Independently Associated with Temporal Discounting and Time Perception

Throughout history, psychologists and philosophers have proposed that good sleep benefits memory, yet current studies focusing on the relationship between traditionally reported sleep features (e.g., minutes in sleep stages) and changes in memory performance show contradictory findings. This discrepancy suggests that there are events occurring during sleep that have not yet been considered. The autonomic nervous system (ANS) shows strong variation across sleep stages. Also, increases in ANS activity during waking, as measured by heart rate variability (HRV), have been correlated with memory improvement. However, the role of ANS in sleep-dependent memory consolidation has never been examined. Here, we examined whether changes in cardiac ANS activity (HRV) during a daytime nap were related to performance on two memory conditions (Primed and Repeated) and a nonmemory control condition on the Remote Associates Test. In line with prior studies, we found sleep-dependent improvement in the Primed condition compared with the Quiet Wake control condition. Using regression analyses, we compared the proportion of variance in performance associated with traditionally reported sleep features (model 1) vs. sleep features and HRV during sleep (model 2). For both the Primed and Repeated conditions, model 2 (sleep + HRV) predicted performance significantly better (73% and 58% of variance explained, respectively) compared with model 1 (sleep only, 46% and 26% of variance explained, respectively). These findings present the first evidence, to our knowledge, that ANS activity may be one potential mechanism driving sleep-dependent plasticity.

/pdf/autonomic-activity-during-sleep-predicts-memory-2fnz9ikwko.pdf

Autonomic activity during sleep predicts memory consolidation in humans.

Time perception is a fundamental component of everyday life. Although time can be measured using standard units, the relationship between an individual's experience of perceived time and a standard unit is highly sensitive to context. Stressful and threatening stimuli have been previously shown to produce time distortion effects, such that individuals perceive the stimuli as lasting for different amounts of time as compared to a standard unit. As a highly social species, humans are acutely sensitive to social stressors; however, time distortion effects have not been studied in the context of social stress. We collected psychophysiological (electrocardiogram and impedance cardiography) and time perception data before, during, and after a modified version of the Trier Social Stress Test for 42 participants. Based on prior theories and evidence from the time perception literature, we hypothesized that experiencing a stressful event would result in time distortion. This hypothesis was supported by the data, with individuals on average reproducing short and long duration negative and positive stimuli as lasting longer after experiencing social stress, t(41) = −3.55, p = .001, and t(41) = −4.12, p < .001 for negative stimuli, and t(41) = −2.43, p = .02, and t(41) = −3.07, p = .004 for positive stimuli. However, changes in time perception were largely unrelated to psychophysiological reactivity to social stress. These findings are in line with some other studies of time distortion, and provide evidence for the interoceptive salience model of time perception. Implications for mechanisms of time distortion are discussed.

The influence of social stress on time perception and psychophysiological reactivity

Emotional distortions of the perceived duration of events are often explained in terms of increases and decreases in arousal. While this explanation is theoretically plausible, there is a lack of evidence for a direct relationship between physiological arousal and perceived duration. The aim of the current study was to investigate whether physiological arousal, defined by autonomic nervous system (ANS) activity is directly related to perceived duration. In two experiments we measured skin conductance level (SCL) and high frequency heart rate variability (HF HRV) during verbal estimation tasks. In Experiment 1, participants estimated the duration of electro-cutaneous stimuli previously rated as inducing no pain, low pain and high pain. High intensity stimuli were perceived as lasting for longer than low intensity stimuli, and these changes in duration estimation were associated with changes in ANS activity. In Experiment 2, participants estimated the duration of a neutral visual stimulus while experiencing different intensities of background thermal pain (no pain, low pain, and high pain), to determine whether task-irrelevant arousal also affects time perception. Duration estimations for the neutral stimulus did not increase with pain intensity despite significant increases in SCL. Furthermore, there was no association between ANS activity and time estimation in Experiment 2. These findings suggest that the relationship between physiological arousal and time perception is more complex than previously described. While physiological arousal can influence the perceived duration of events, it appears to have a greater capacity to do so when the to-be-timed stimulus is itself the source of arousal. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

/pdf/the-relationship-between-pain-induced-autonomic-arousal-and-323owfbeog.pdf

The relationship between pain-induced autonomic arousal and perceived duration.

Virtual-reality
(VR) users and developers have informally reported that time seems to pass more
quickly while playing games in VR. We refer to this phenomenon as time compression: a longer real duration
is compressed into a shorter perceived experience. To investigate this effect,
we created two versions of a labyrinth-like game. The versions are identical in
their content and mode of control but differ in their display type: one was
designed to be played in VR, and the other on a conventional monitor
(CM). Participants were asked to estimate time prospectively using an
interval production method. Participants played each version of the game for a
perceived five-minute interval, and the actual durations of the intervals they
produced were compared between display conditions. We found that in the
first block, participants in the VR condition played for an average of 72.6
more seconds than participants in the CM condition before feeling that five
minutes had passed. This amounts to perceived five-minute intervals in VR
containing 28.5% more actual time than perceived five-minute intervals in
CM. However, the effect appeared to be reversed in the second block when
participants switched display conditions, suggesting large novelty and
anchoring effects, and demonstrating the importance of using between-subjects
designs in interval production experiments. Overall, our results suggest
that VR displays do produce a significant time compression effect. We discuss a
VR-induced reduction in bodily awareness as a potential explanation for how
this effect is mediated and outline some implications and suggestions for
follow-up experiments.

/pdf/time-compression-in-virtual-reality-30nu7r61gc.pdf

Ilenia Levorato

Papers

Heart rate variability helps tracking time more accurately.