Authors: Claudia Hammond
The same David Eagleman who throws people backwards off buildings has another idea which, like Buonomano’s theory, relies on the idea that our brain cells possess inherent properties of timing. When you look at a picture it takes a certain amount of energy for the neurons in your brain to identify what you are seeing. Think back to the giraffe/mango task, where people who are shown a series of pictures of giraffes with a surprise mango in the middle insist that the mango was present for longer than each giraffe. Registering the giraffe the first time uses a certain amount of energy. On seeing an identical giraffe picture the brain doesn’t need to waste as much energy considering it. Eagleman’s theory is that our sense of duration is based on the amount of neural energy used. So the first picture of the giraffe would take more energy and therefore seem longer, while subsequent giraffe pictures use less energy and seem shorter. Then up pops the mango. It’s new and
requires more energy for the brain to register what it is, so it appears to be present for longer. In terms of the evidence for this idea, it is true that rates of neuronal firing do increase when there’s a new picture and drop off when the pictures repeat. Whether this is exactly how we calculate timings remains to be seen, but it is certainly a plausible idea. We know that novelty does play a part in timing, even at longer durations. If you arrive in a new city and walk from your hotel to a restaurant, the processing of all the new sights and sounds will use up a lot of neuronal energy, which will give the impression that the journey has taken a long time. The walk back, along a route now more familiar, will seem shorter.
The idea that neuronal activity itself might be used to measure time could also explain the difficulties that people with schizophrenia can have with time perception. Unlike voice-hearing or delusional thinking, this symptom tends to be less well-known, but some people find they are no longer able to view the present while simultaneously remembering the recent past and anticipating the future. The philosopher Edmund Husserl believed that holding these three time-frames in mind was essential for consciousness and for giving us a firm sense of reality. In schizophrenia this can be disrupted, making time feel unreal. People with schizophrenia find it hard to spot the oddball in an experiment or even to detect flickering lights. Their neural responses suggest that everything they see seems fresh and new. Usually when you show someone the same giraffe again and again their neural response diminishes, but not with people with schizophrenia.
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We can predict the timing of everything from the swinging of a pendulum to a car door closing without trapping our fingers. We don’t even notice these small timing judgements that we make hundreds of times a day. But imagine how unsettling it would be if they started to appear to be out of kilter. Add to this the disturbance of your thoughts. If you have lost all cues to temporal reality and have no way of ordering your thoughts chronologically to identify which are memories, which are daydreams and which is the reality here and now, it is no surprise that a psychotic episode can feel terrifyingly disorientating. Philosopher and neuroscientist Dan Lloyd goes as far as to suggest that a disorder of temporal perception might even account for some of the symptoms clustered under the diagnosis of schizophrenia. This makes sense. I’ve already mentioned the influence of dopamine in time perception and one of the theories for the cause of schizophrenia, ‘the dopamine hypothesis’, implicates this neurotransmitter. It is possible that dopamine in effect sets the mind’s clock, dictating the rate of the pulses, and that some symptoms of schizophrenia could result from a disruption to the clock.
Eagleman’s theory can also explain the stopped clock illusion. The initial tick seems longer because it’s the first time your brain has registered the movement of the second hand, then the neuronal firing and the energy used drops off and so does the perception of time passing as the second hand continues on around the clock face. Likewise a bright light that’s turned on momentarily appears to last longer than one that is more faint and an interval filled with a
complex piece of music seems longer than one with a simpler piece. Is this because we are timing them via the energy used to process them?
I realise I have covered a lot of different theories here. My best guess, based on the available evidence, is this: that pulses which are already being used for other purposes are measuring time in our brains. They might be ripples, they might be energy packets, but, whichever they are, when we turn our attention to time itself, they speed up. This acceleration, which you might recall from the discussion of the sheep going through the gate, gives the impression that time is dilating. Extreme anxiety also speeds up the pulses, so while Chuck Berry desperately tries to save his own life the pulses get faster and time gets slower. To estimate a length of time, we use the dopamine system along with combinations of those four crucial areas of the brain – the cerebellum, the basal ganglia, the frontal lobe and the anterior insular cortex – depending on the time-frames involved.
Once again this illustrates the central theme of this book – that we are creating our own perception of time, based on the neuronal activity in our brains with input from the physiological symptoms of our bodies. This could seem like a reductionist explanation, that time is simply chemical, something created by neuronal activity in concert with the dopamine system, but these neuroscientific explanations should not reduce the importance of our subjective experience of time. For Chuck Berry or Alan Johnston or even Michel Siffre lying in his cold sleeping bag in his ice cave, the pulsing of neurons meant nothing. It was the experience that mattered and this is the part we can change. We have
multiple skills when it comes to considering time. We can mentally throw ourselves forward into the future or back into the past. We can imagine situations in the future that we have never witnessed, we can put events into chronological order, detect rhythm in music, speak, catch a ball, run for a train, cross the road and all without needing any awareness of what’s happening in the brain.
Yet this reality we create for ourselves can easily get disturbed. Eleanor finds it hard to judge time without a clock. How much harder would it be with no daylight and no one else to ask?
OPERATION TIME
For two months, or 1,500 hours, Michel Siffre had lived in total isolation underground in the French Alps with no idea whether it was night or day. He allowed his body to tell him when to rest and went to bed whenever he felt tired, describing this body-dictated sleep as more perfect than he could ever have above ground. He ate when he was hungry. But he soon lost his appetite. The one advantage of the low temperatures was that his food stayed fresher for longer than he had expected, but he was no cook and his attempts to make rice pudding went so wrong that he had to open a tin of pineapple chunks to take the taste away. In the end he found he only really enjoyed bread and cheese. Each day he read, kept a diary and noted down physiological measurements from the electrodes fixed to his head and chest. The experiment he had dreamed of conducting for so long was going well, but he was becoming increasingly
miserable. His mattress was made from a thick piece of sponge, but because it lay on a floor of ice in below-freezing temperatures, the bed was often damp. His feet were permanently wet and the air permanently dank. His clothes never dried out overnight, so he would put them back on next day and shudder at the bitter wetness against his skin. After spending so many hours sitting down each day he developed back pain, but was determined not to take painkillers in case they interfered with his physiological experiments.
Michel found himself passing the hours by contemplating another time entirely – the future. He tried to find ways to entertain himself; his version of quoits involved attempting to throw sugar lumps into a pan of boiling water. A record player had been lowered down the shaft for company, but Beethoven and Mario Lanza weren’t a success. ‘The symphonies that had once charmed me became merely chaotic noise. And the popular songs sung by the best café singers seemed only to increase my feeling of loneliness.’ He was so lonely that the only thing he describes with any real pleasure in his diary is a spider he captured and kept in a box as a pet. He talks of often looking at her and feeding her tiny amounts of food and liquid.
However, despite the wet conditions and his increasing hatred for the yellow lining of his tent, he became so fond of his makeshift home that he began to spend more and more time in bed, leaving the tent as infrequently as possible. When he did venture out into the cave to take measurements he loved to look back and see his cosy, freezing home glowing in the dark. He soon lost interest in keeping the cave tidy and allowed the rubbish to pile up outside the
front of his tent. The low temperatures meant that the food was slow to rot, but he did notice mildew growing on an apple core and, ever on the look-out for an opportunity to experiment, he left a line of apple cores so that someone could check on the mildew’s progress the following year.
With no daylight Michel developed a squint and found it increasingly hard to distinguish green from blue. He didn’t feel claustrophobic, but towards the end of his underground stay he was experiencing dizzy spells and afterwards doctors confirmed that his body had entered a state they called ‘incipient hibernation’.
Throughout his stay two members of the team remained above ground at the cave’s entrance, sitting in baking sun during the day and lying in freezing temperatures at night. They were forbidden from contacting him lest this give him a clue as to the time of day. Instead, a telephone line had been rigged up which linked him with the surface and he called them whenever he woke, ate or was planning to sleep. They were under instruction to keep a record of the precise hour at which he phoned, but not to reveal it to him. By the second morning Michel was already two hours off-kilter. Within a week he was two days behind reality. Within 10 days he thought night was day and even noted in his diary that with their cheery ‘Hellos’ the team sounded as though they’d been up for hours. In fact he had woken them yet again in the middle of night.
During each phone call he took his pulse and counted from 1 to 120 at the rate of one digit per second. But here something extraordinary happened. He thought the count took the two minutes that it should, but his colleagues with
the stopwatch knew it was taking five minutes. Life without day or night had skewed his mind time. He had lost any accurate sense of the passage of hours or minutes and found he couldn’t even guess how long his phone call to the surface had lasted. Initially he used his Mario Lanza records to judge short periods of time, but soon, ‘The beginning and the end of a record blend and become integrated in the flood of time . . . Time no longer has any meaning for me. I am detached from it, I live outside time.’ Time had become something he could no longer judge, something he found strange.
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He was undoubtedly bored and lonely, yet found that although each day felt endless, when he looked back he thought it had lasted far fewer hours than it really had. This is a common paradox of time. Yet it was passing even faster than he realised. He eked out his cheese rations to make it last the whole two months, but he was so wrong about time that in fact he needn’t have deprived himself.
He did have a suspicion that he might not have the right date, that he might be a few days ahead, but insisted he couldn’t possibly be behind. Then the team suddenly announced that the experiment had come to an end and that it was already 14 September. He was astonished. He thought he had 25 days to go. But the discovery that he could now leave the damp cave behind and emerge into the sunlight did not bring him joy. Instead he was confused. He felt he had lost his sense of reality and as a result had lost 25 days. Where had that time gone? He felt cheated of his memories.
Then time warped once again. Although he was expecting to stay for almost another month, as soon as he discovered that the team were on their way down to fetch him, time
felt unbearably slow. Even in the last few minutes before their arrival he wondered how they could be taking so long. He had always known that once the team arrived they would have to spend one more night underground getting everything ready for the ascent, but now he felt too impatient to wait. And he was afraid. He found himself overcome with the fear that having survived this long, he might die right at the last moment. The sound of every tiny rock fall or crack in the ice made him flinch. Finally his friends reached him and he felt calmer. They were disgusted by his rubbish tip, which was by now waist-high, but relieved to see that he was okay. At the last moment he delayed leaving. He knew the press was camped out on the surface waiting for his glorious arrival, but he continued collecting samples from inside the cave until his colleagues told him he really must stop.
The journey back to the top was tough. In his weakened state he had to be winched up on a platform, but even so he blacked out and almost gave up when he had to climb using his own strength through what they called the cat hole. They covered his eyes to shield him from the daylight. He blacked out again and was rushed to a helicopter, but not before his friend Anne-Marie had held some fresh violets to his nose for him to smell. This was to become a very strong memory for him; the first nice smell he had experienced in two months.
Some claimed the whole operation had been nothing more than a publicity stunt and that the phone contact meant he wasn’t truly living in isolation, but most accepted that at the age of 23 Michel had founded the field of
chronobiology – the scientific study of the effect of time on biological rhythms. His experiments demonstrated for the first time the existence of a body clock that can function independently of light and dark. Before Michel’s experiment no one knew how the body’s rhythms worked, but analysis of his sleep and wake cycles revealed that regardless of the time of day, if a series of sleep and active periods were added together they always came to 24 hours and 31 minutes. This is the one clock in the body that we can precisely locate. It is in a part of the hypothalamus gland at the base of the brain called the suprachiasmatic nucleus. The neurons here oscillate constantly, providing a rhythm of just over 24 hours which is corrected by daylight.
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Because Michel had no daylight he began doing what is known as free-running and each day he became another 31 minutes out of synch. Eventually he became so off-kilter that he was sleeping during the day rather than at night, yet his body was keeping to a surprisingly regular routine.