Time Perception, Memory & Focus | Huberman Lab Essentials

The Foundation of Time Perception: Entrainment [00:50]

• The most fundamental aspect of time perception is entrainment, the way internal biology and psychology are linked to external factors.
• Circannual rhythms, a year-long biological calendar system, are influenced by the changing day length throughout the year.
• Light seen by the eyes inhibits melatonin release; more light means less melatonin, and less light means more melatonin.
• Melatonin levels correlate with day length, affecting sleepiness and regulating hormones like testosterone and estrogen.
• The brain averages light exposure to precisely measure time across the year, influencing energy levels and mood seasonally. Spring, with increasing daylight, leads to less melatonin and generally more energy.
• Winter, with decreasing daylight, leads to more melatonin and generally less energy and a lower mood.
• Melatonin acts as a signal for the internal state to match external events like the Earth's rotation around the sun.

The amount of melatonin in your brain and body that's released tends to be less when days are long. When days are very short, the amount of melatonin that's released and the duration that that melatonin exists in your brain and body tends to be much longer.

The Circadian Clock and Its Impact [04:22]

• The circadian time cycle, a 24-hour rhythm, is a powerful internal clock that none can escape.
• This clock resides in the suprachiasmatic nucleus, located above the mouth, and its cells fire on a regular rhythm, dictating periods of activity and sleep.
• Every cell in the body exhibits a 24-hour oscillation in gene expression, entrained to the external light-dark cycle.
• Morning sunlight, evening sunlight, and darkness at night ensure these cellular oscillations match the external environment.
• Precise circadian entrainment is vital, as disruptions lead to severe health problems, including increased cancer risk, obesity, mental health issues, decreased wound healing, and impaired physical and mental performance.
• Simple protocols for circadian entrainment include viewing 10 to 30 minutes of bright light (ideally sunlight) within an hour of waking and again in the afternoon/evening, while minimizing bright light exposure in the evening.
• Engaging in physical activity at regular times also helps entrain the circadian clock.

Disruptions in circadian entrainment cause huge health problems. They increase cancer risk. They increase obesity. They increase mental health issues. They decrease wound healing. They decrease physical and mental performance. They disrupt hormones.

The Effect of Circadian Disruption on Time Perception [07:00]

• Studies where people were isolated from clocks and natural light revealed significant disruptions in time perception.
• Participants in these studies generally underestimated how long they had been in the isolated environments. For instance, after 42 days, some estimated they had only been there 8 or 36 days.
• Perception of shorter time intervals, such as measuring off 2 minutes, was also greatly disrupted when circadian entrainment was compromised.
• This disruption in perceiving time on shorter scales can lead to problems in managing work and daily challenges.
• Accurate perception of time is fundamental for performing tasks effectively and predicting performance levels.

What they found is that people underestimate how long they were in these isolated environments.

Ultradian Rhythms and Cognitive Focus [09:02]

• Ultradian rhythms are cycles of about 90 minutes that influence our daily activities.
• Sleep is broken into 90-minute ultradian cycles, and many waking activities are also governed by these rhythms.
• The brain can enter a state of focus and alertness for approximately 90 minutes, after which there is a significant drop in the ability to sustain mental or physical work.
• This 90-minute cycle is linked to the release of neurochemicals like acetylcholine and dopamine, which enable focus.
• After about 90 minutes, the availability of these chemicals decreases, diminishing focus.
• To leverage these cycles for productivity, it is recommended to limit hard work to 90 minutes or less.
• Multiple 90-minute focus cycles per day should be spaced by at least 2 to 4 hours, as continuous cycles are not sustainable due to neurochemical limitations. Most people can manage about two such cycles per day.

The 90-minute time block seems to be the one in which the brain can enter a state of focus and alertness and do hard work and focus, focus, focus.

Three Forms of Time Perception [13:12]

• There are three primary forms of time perception:
  • Perception of time in the present: How quickly or slowly events seem to be happening, akin to an interval timer.
  • Prospective timing: Measuring off time intervals into the future, like using a stopwatch.
  • Retrospective time: Measuring off time in the past, using memory to reconstruct the sequence and duration of events.
• These perceptions are governed by neuromodulators like dopamine and serotonin.

We have interval timers. We also engage in what's called prospective timing, which is like a stopwatch, measuring off things as they go forward. There's also retrospective time, which is how you measure off time in the past.

Neuromodulators: Dopamine, Norepinephrine, and Serotonin [15:11]

• Dopamine and norepinephrine are neuromodulators that increase the overestimation of elapsed time.
• When dopamine levels rise, individuals tend to perceive that a minute has passed before a full minute has actually elapsed.
• Conversely, serotonin causes people to underestimate the amount of time that has passed.
• These neuromodulator levels fluctuate throughout the 24-hour circadian cycle.
• Dopamine and norepinephrine are generally elevated in the first half of the day, while serotonin levels increase towards evening and nighttime.
• This fluctuation impacts our perception of time, suggesting that tasks requiring intense focus might be better suited for the earlier part of the day when dopamine and norepinephrine are higher.

The more dopamine that is released into our brain, the more we tend to overestimate how much time has passed.

Trauma, Overclocking, and Memory Encoding [19:03]

• Trauma can lead to a phenomenon called "overclocking," where extreme increases in dopamine and norepinephrine cause time to be perceived in ultra slow motion due to a significantly increased frame rate.
• This heightened perception during traumatic events results in memories being "stamped down" into the memory system with extreme precision.
• The memory system records both the spatial code (which neurons fired) and the rate code (how quickly they fired), allowing for flexibility in memory storage.
• Overclocking during trauma results in memories being stored with an excessively high frame rate, making them very difficult to shake and preserving associated emotions.

Overclocking is when levels of dopamine and norepinephrine increased so much during a particular event that we fine slice.

The Paradoxical Relationship Between Present Experience and Memory [24:08]

• Dopamine influences how we perceive time in the present and how we remember it in the past, often in opposite ways.
• Fun, varied, and exciting experiences (associated with increased dopamine) feel like they pass quickly in the moment but are remembered as being longer due to the richness of encoded details.
• Conversely, boring or disliked experiences feel like they take a long time in the moment but are remembered as being shorter.
• This suggests we have two "stopwatches": a dopamine-driven one that fine-slices time with high resolution and another that captures larger time bins.
• The choice of stopwatch depends on our level of excitement and engagement.

If something that you experience is fun or varied, meaning it has a lot of different components in it and is in other words is associated with an increase in dopamine in your brain. You will experiencing experience that as going by very fast.

Habits, Dopamine, and Carving Up Time [28:41]

• Dopamine plays a crucial role in setting the "frame rate" of our perception of everything, not just positive or negative events.
• Habits and regular routines can serve as a powerful tool to manage this.
• Incorporating specific habitual routines at regular intervals throughout the day creates "functional units" of time.
• These routines, by causing dopamine release, not only provide motivation but also mark specific times of day as the beginning of a distinct time bin, helping to structure our experience of the day.

Placing specific habitual routines at particular intervals throughout your day is a very not just convenient, but a very good way to incorporate the dopamine system so that you divide your day into a series of what I would call functional units.