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August 1 - October 17, 2021
The stopped clock illusion arises because the pause in the movement of the second hand seems to last longer than what your brain thinks a second should last. The illusion seems to be caused by the fact that on the brief scale of a second or less, our own actions, in this case shifting our gaze, can warp our sense of time.12
For better or worse, however, the convention is that statements about time speeding up or slowing down refer to the apparent speed of an external clock in relation to a hypothetical internal clock—even though it is obviously the internal clock that is actually doing the slowing or speeding.
More generally, it is important to note that our feeling of how quickly or slowly time is passing is not necessarily equivalent to our explicit estimates of how many seconds or minutes have elapsed
Furthermore, some drugs can affect people’s judgments of short intervals but not long intervals, and vice versa.20
Overall, the scientific literature on the effect of psychoactive drugs on time perception indicates that there is no single neurotransmitter that governs our perception of time.
Hypermemory. Another possible explanation for the slow-motion effect is that it is an after-the-fact illusion—an illusion in the sense that people don’t actually perceive events happening in slow motion at the time of the accident, they just think they did when they are recalling the episode.
This is thought to be one explanation of so-called flashbulb memories—those in which people remember where they were when they heard of a tragic event such as 9/11. Post-traumatic stress disorder is another example in which the fight-or-flight response enhances memory, in this case resulting in overpoweringly strong and maladaptive memories.27
The hypermemory hypothesis, of course, does not account for reports of people acting more rapidly and with more clarity than they otherwise could.
The illusory nature of body awareness can be unveiled by phantom-limb syndrome.
Thus, it is not really the phantom limb that is the illusion, but the sense of ownership of our actual limbs. Phantom-limb syndrome is a puzzling phenomenon, but focusing too much on the mystery of phantom limbs distracts from the real puzzle: how the brain creates conscious awareness of our body to begin with.28 Similarly, focusing on the slow-motion effect in life-threatening situations distracts us from the real mystery: our “normal” perception of the passage of time.
Our normal sense of time is a mental construct, one that also seems to have different speed settings. The metaillusion hypothesis emphasizes that the slow-motion effect is an illusion of an illusion,
Consciousness is a delayed account of not only what is happening in the external world, but of what is happening in the unconscious brain.
We think of the slow-motion effect and other temporal illusions as distortions of our perception of time—more specifically of the rate at which things change—but it is not that simple. Our ability to compress and dilate time is actually a feature of the brain that we use every day.
To psychologists and neuroscientists these illusions have provided valuable insights into how the brain works, but in the end perhaps the most important lesson is that, distorted or not, all subjective experiences are in essence illusions.
mondegreen.
That was a good idea can be either a compliment or a put-down depending on the prosody of the speaker.
Infant-directed speech is often characterized by an increase in pitch, longer vowels, and longer pauses between words. For example, studies show that when adults are talking among themselves, the pauses between phrases are around 700 milliseconds, but when adults are speaking to babies this value increases to over a second.
Speech and music are the temporal equivalent of recognizing a visual scene: they require solving a hierarchy of embedded temporal problems.6
So as far as the central nervous system is concerned, discriminating the pitch of sounds is essentially a spatial task—akin to the differences in the location of the keys on a piano. Morse code is independent of pitch or spatial information of any sort—in Morse code timing is everything.
Messages can even be sent with short and long eye blinks. This was famously done by the American admiral Jeremiah Denton during the Vietnam War. As a prisoner of war he was interviewed for propaganda purposes, and during the televised interview he answered a question by saying “I get adequate food and adequate clothing and medical care when I require it.” But as spoke he blinked: T O R T U R E.7
In other words, people learn Morse code by starting with Morse code motherese.
One might guess that the brain uses some sort of all-purpose neural stopwatch to time all durations in the range of a few milliseconds up to a second or so. On the other hand, we might speculate that the brain has a multitude of different neurons or circuits each specialized for detecting a given interval, akin to having a collection of hourglasses—one for each possible interval. To attempt to distinguish between these hypotheses we can ask if, and how, people’s ability to discriminate intervals improves with practice.
Generally speaking, what matters is not the absolute difference between the two stimuli, but the relative ratio between them.
Although ten days of practice on the 100 ms intervals dramatically improved people’s ability to discriminate intervals around 100 ms, it did not improve the interval discrimination thresholds for the 50, 200, or 500 ms intervals at all.9 If learning on the 100 ms interval came from improved focus, then subjects would likely improve on all intervals, but we did not observe that. More importantly, this result, which has since been replicated in numerous other studies,10 suggests that however the brain is telling time in the subsecond range, it does not seem to be via any sort of master stopwatch
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But even among musicians there are significant timing differences. Drummers, for example, have been shown to discriminate 1 sec intervals better than string musicians.12 Overall, studies reveal that musicians generally perform at least 20 percent better than nonmusicians in a variety of temporal tasks.
Do we understand the concept of time because we are capable of mental time travel, or do we engage in mental time travel because we grasp the concepts of past, present, and future?
The feeling of the passage of time—our perception of change—is also a mental construct. To the neuroscientist this construct is correlated with reality: we perceive waves crashing and birds diving into the water because time is actually flowing—these events are unfolding in a universe in which only the present is real. To many physicists and philosophers the flow of time is also a mental construct, but of something that holds no equivalent in the physical world. Within the block universe of eternalism our feeling of the passage of time is more akin to the visions of a schizophrenic, something
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consciousness itself is generated in a highly discontinuous manner. The unconscious brain delivers stories to the conscious mind in fits and starts.
vision is partially suppressed during saccades.1
According to one estimate, between saccades and blinks, a full hour of visual information is lost throughout the course of a day, without any perceived blanks in our visual stream of consciousness.2
The time span during which the brain integrates visual and auditory information into a single unified percept is called, appropriately enough, the temporal window of integration. Within this window, subjectively speaking, the brain considers the auditory and visual events to be simultaneous. The windows can be over 100 milliseconds for speech—for example, if there is a mismatch of less than 100 milliseconds between the audio and visual tracks of a movie, it rarely comes to our attention.
But the window is asymmetric—that is, if the auditory signal precedes the visual signal by 50 milliseconds, subjects may notice something is awry, but not if the auditory follows the visual signal by 50 milliseconds.4
As explained by the French neuroscientist Stanislas Dehaene: “Not only do we consciously perceive only a very small proportion of the sensory signals that bombard us, but when we do, it is with a time lag of at least one-third of a second. . . . the information that we attribute to the conscious ‘present’ is outdated by at least one-third of a second. The duration of this blind period may even exceed half a second when the input is so faint that it calls for a slow accumulation of evidence before crossing the threshold for conscious perception.”11
spatial summation,
temporal summation,
fact that all mental states are produced by a pattern of neural activity within the brain, and any given neural pattern is produced by the interaction of the previous neural state (both the active and hidden states discussed in chapter 6), the current external input, and stochastic fluctuations occurring at the thermodynamic and quantum levels.
The notion that free will is merely a feeling that occurs after consciously inaccessible circuits make a decision can be unsettling. Indeed, it has been argued that if this were the case, then consciousness would be useless, “the proverbial backseat driver, a useless observer of actions that forever lie beyond its control.”25
In general relativity, time (as a constituent of spacetime) can be thought of as part of the fabric of the universe, whereas in quantum mechanics time is a parameter that governs the evolution of a quantum system. Puzzlingly, however, some mathematical attempts to merge general relativity and quantum mechanics end up without any role for time whatsoever. The time parameter simply disappears from the equations,30 leaving one with the impression that we actually live in a block universe composed only of three spatial dimensions.
A further conflict between physics and neuroscience is that if the flow of time is an illusion created by the mind, then instantaneous slices of the block universe must be able to sustain the phenomenon of consciousness.
Neuroscientists and psychologists in turn must acknowledge the fact that the brain is at its core a temporal organ. If one were to unwisely attempt to summarize the function of the brain in three words, those words might be anticipate the future. The brain tells time, generates temporal patterns, remembers the past, and endows us with the ability to mentally project ourselves forwards in time—all in order to predict and prepare for the future.
Mental time travel requires a delicate balance of science and art: rigorous extrapolation of the remembered past and dreaming up the inconceivable. This balance can go awry.
