​Our brain is the seat of our consciousness of the self and of the world. It orchestrates myriads of bodily information and regulates the flow of our thoughts accordingly. In the incessant flow of life, how does the brain manage to stabilize our relationship with time and give rise to that intimate feeling of "time passing"? A founding hypothesis of cognition is that the continuous flow of information is segmented by the brain into discrete, manipulable events, so that our brains attribute to physical time abstract properties (so-called mental representations) such as duration (measurement of a time interval) and speed (rate of change per unit of time).

Time perception during the Covid-19 pandemic

Psychological time is influenced by multiple factors such as wakefulness, emotion, attention, boredom or even memory. The causal link between these factors and the conscious experience of time is typically not (or only marginally) accessible to the individual. For example, mental workload is negatively correlated with the perception of duration: the more we are engaged in a demanding task, the less we pay attention to time, and the more this time fades from our memory (to the benefit of the information processed during the task). While this laboratory observation is well documented, it remains to be seen whether such cognitive effects on time perception are reproduced in real life. This first study exploits a dataset collected online during the Covid-19 pandemic, where participants performed a working memory task in which their cognitive load was parametrically manipulated (see Joliot news). The idea was to test whether the amount of information stored in working memory affected the perceived duration and speed of the passage of time, depending on whether the participant directed his attention to time (prospective time) or not (retrospective time). The results show that duration and speed are differentially affected by social isolation. Taken together, these observations lead the authors to discuss the influence of cognitive load on different experiences of time.

Experiential time, or how to apprehend the perceived duration and the speed of time?

In a second publication, the authors questioned the link between the phenomenology of duration and speed. To do so, they studied how the density of events affected these two temporal experiences in a context that is, after all, typical of our daily lives: waiting for a train to arrive... but in virtual reality! Participants waited on a station platform for a few seconds, during which a different number of events could occur (see below the 2 videos associated with this study). At the end of the sequence, participants had to classify the video as short or long (duration task) or as fast or slow (speed of passage of time task). The researchers found that a large number of events lengthened subjective duration and accelerated the passage of perceived time. In particular, the duration and density of events affected the estimation of duration, while the rate of change affected the perceived speed of the passage of time. Surprisingly, participants were also faster at estimating speed than duration: could perception of duration be derived from speed, rather than vice versa? Overall, these results suggest that distinct neuronal mechanisms underlie these two phenomenological experiences of time.
    See the 2 videos associated with M Lamprou-Kokolaki's article:
    - https://youtu.be/f5HGAv1-Fdc
    - https://youtu.be/d1V7qc5C--o

Alpha brain-wave bursts would indicate episodic time

In this third study, the authors explore the question of duration in an experimental context and on a time scale relevant to everyday life. The minimalist experimental approach explores so-called "alpha" brain rhythms (~7-14 Hz), which are markers of the human state of consciousness. The hypothesis that these rhythms might incarnate the internal clock that governs our awareness of time goes back more than a century, without tangible proof until this study. Indeed, the initial postulate was incompatible with the non-stationary nature of these brain rhythms, which are characterized by irregular intermittent or oscillatory bursts of activity over time. Based on non-invasive magnetoencephalography recordings, the authors show that alpha wave bursts, generated by the human brain, can track the passage of time and contribute to the experience of time. In fact, over a given period, the relative duration of alpha wave bursts reliably indicates the participant's retrospective estimate of the duration experienced. Remarkably, this relationship holds true only when the individual is not paying attention to time, and disappears when he or she is. These observations suggest that, on a scale of a few minutes, alpha brain activity marks our temporal experience, shedding new light on how our brains manage time.

Through very distinct approaches (laboratory behavior, real-life situations and neuroimaging), all these results converge on the fact that duration and the passage of time are two mental constructs governed by partially distinct cognitive operations and neuronal processes. The representation of time lived in the present moment (time) and the representation of time remembered (memory) forge the labyrinth in which our self-awareness and our temporal positioning in a world in perpetual motion are interwoven.

Contact: Virginie van Wassenhove (virginie.van-wassenhove@cea.fr)​

 See also the team website