How do we sense time?

The Brain’s Video Camera

To our mind, the world appears to be continuous. When we say that the world is continuous, we mean that it is persistently active and undergoing continuous change as time goes on. However, neuroscientists have accumulated a sizeable amount of evidence indicating that the way we perceive reality and process sensory information is not continuous but actually discrete. In other words, it seems that our brains do not process reality as a continuous stream but rather in discrete chunks, or mental snapshots, each having a short duration, similar to how a video camera records a series of still snapshots on film. Our experience of the world only appears continuous in the same way that a movie appears continuous even though it is made up of discrete still images replayed in a rapid sequence.

Buddhists’ holy texts were among the earliest sources to propose that consciousness is not continuous but consists of a sequence of extremely fast discrete events referred to as ‘momentary collections of mental phenomena’ or ‘distinct moments’. Numerous philosophers also put forward similar notions in the 18th century, such as David Hume who noted that the stream of our thoughts is ‘nothing but a bundle or collection of different perceptions, which succeed each other with inconceivable rapidity. The mind is a kind of theatre, where several perceptions successively make their appearance.’  The speed of thought is the speed at which these perceptions are processed in the brain.

According to Francis Crick, Nobel Prize winner, biophysicist, and co-discoverer of the DNA molecule structure, the consciousness not only comes in discrete mental snapshots, but the experience of motion is itself illusory; “perception might well take place in discrete processing epochs, perceptual moments, or snapshots. Your subjective life could be a ceaseless sequence of such snapshots.” In that sense, life is a movie, your eyes are the lens, and your brain is the video camera.

Slow-Mo- Mode

If you own one of the latest iPhone or Android smartphones, you might have noticed a video recording feature called ‘Slo-Mo’ mode. It is normally used to capture fast action sports or racing scenes and renders them in slow motion. In the normal video mode, a scene is usually recorded at a speed of 30 frames per second (fps) but with the Slo-Mo mode, the latest models now boast cameras that are fast enough to capture videos at a recording speed of 240 fps. If you switch your smartphone to that high-speed recording mode and capture a fast action scene at 240 fps, you will notice that when the scene is later replayed at the normal speed of 30 fps, it will appear in slow motion, exactly as if time had slowed down. The reason for that slow-motion effect is that, when filming at 240 fps, every second will contain 240 frames which will be spread over 8 seconds when they replayed at the normal speed of 30 fps. Therefore, every second that is captured at the fast recording speed will appear 8 times longer and time will seem to be running slowly.

This is similar to what goes on inside our brains. Let us assume that we perceive the world at an average speed of 10 mental snapshots per second. Every time our brain captures 10 snapshots, it assumes that one second has elapsed. Now imagine that your brain’s processing speed is suddenly given a boost, say from a dose of drug stimulants such as LSD or amphetamine drugs (speed), which causes a surge in brain electrical activity and allows the brain to start capturing 20 snapshots per second. Under normal circumstances, 20 snapshots would have taken two seconds to record at the brain’s normal recording speed of 10 fps. When those 20 snapshots are processed, the brain assumes that they must have spanned a period of two seconds instead of the one ‘real’ second that was actually needed to record them. One second of ‘real’ time will contain 2-seconds worth of information and will, therefore, appear to have stretched, as if time had passed slowly. Such experiences, as we shall see later in more detail, have been confirmed by people who take drugs that stimulate the brain. The faster our brain is at processing sensory information, the slower time appears to run. The speed at which we experience the flow of time is nothing but the speed of our thoughts.

Silent Movies

The converse can also explain how time seems to fly in certain situations. In the 1920s, when movie making was still in its early days, silent films were recorded at a slow speed of 16 frames per second and had to be replayed at much higher frame rates to look continuous and real. This made the movie appear as if it was running in fast-forward mode. Charlie Chaplin style movies are a perfect case in point; everything moves literally faster than normal as if time was running fast. This analogy helps us understand what goes on in the brain when it records fewer mental snapshots per second, say 5 fps instead of the normal 10 fps, for the sake of demonstration. This means it will need two seconds to capture the 10 snapshots it normally captures in one second. When those 10 snapshots are processed, the brain assumes that the two seconds it took to capture them in just one second. At that rate, two minutes will seem like just one minute and the day will be over before you know it. The slower the brain’s information processing speed, the faster time seems to run.

For more on that check out my book “The Power of Time Perception” to learn more how we perceive time, the factors that affect the speed of time in your mind, and ways to slow it down.

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