Authors: Claudia Hammond
THE MAN WHO THOUGHT THE WORKING DAY HAD FINISHED
A man sat in the consulting room at the Santa Lucia Foundation on the outskirts of Rome waiting to see Dr Giacomo Koch. Back in the sixties the hospital looked after war veterans, now it specialised in neurological damage and the man was hoping the specialists would be able to help him. He was only 49 years old, yet was finding it hard to concentrate and for a few days he had felt a bit weak down one side of his body.
The case was an intriguing one. The man was convinced something quite serious was wrong, but the doctors could not diagnose a recognisable condition. They ran test after
test. To check his memory there was the Digit Span, the Corsi Span, the Rey-Osterrieth Complex Figure test (immediate and delayed recall), the Verbal Supraspan and the Forward and Backward test. To test his visuospatial skills there were the Raven Progressive Matrices. For concentration there was the Trial Making test, for language the Verbal Fluency and Phrase Construction tests. For decision-making there were the Tower of London and Wisconsin Card Sorting tests. The doctors calculated his scores. They were all normal. They had him copy drawings, learn lists of words and complete well-known phrases. Still his scores were normal.
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But the man had also reported another strange sensation; his mind clock and the actual clock seemed to be radically out of synch. He would go into the office, do what felt like a day’s work, get ready to leave and find it wasn’t even lunchtime. On other occasions, events seemed to last for a much shorter time than was the actual case – a minute to him seemed like just 30 seconds.
In the light of this, the doctors performed some time-estimation tasks. In order to get a fair baseline measure, they arranged for eight volunteers, also in their forties, to take the same tests. Each sat alone in front of a computer screen while a series of random numbers appeared one at time. Their task was simply to read the numbers out loud. This would prevent them from counting time in their heads. Afterwards all they had to do was to guess how long the tests had taken. The results of one trial could be down to chance, so they repeated the task with different numbers until they had done it 20 times. In each
instance, the man performed worse than the eight volunteers. His ability to judge the passage of time was somehow impaired.
A brain scan indicated some damage to the right frontal lobe, which as the name implies is near the front of the brain on the right. This gives us a clue as to the next area of the brain implicated in time perception, an area we would normally associate with the ability to hold something in mind known as working memory. It is this skill that allows you to read through a recipe, then remember the list of ingredients while you go to the cupboard to fetch them. The very front of the frontal lobe, the pre-frontal cortex, which is located behind the forehead, seems to be particularly crucial.
The involvement of this area of the brain in time-keeping is backed up by the curious new finding that children with Tourette’s syndrome have recently been found to be better than other children at judging durations of just over a second.
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Suppressing their tics involves activity in the prefrontal cortex and experts have found those children with Tourette’s who were particularly good at suppressing their tics did even better on the timing tasks. This suggests that their need to use this region of the brain to control their tics brings an added advantage in terms of time perception.
So far we have looked at two areas of the brain associated with time perception – the cerebellum, low down at the back of the brain for those millisecond judgements, and the frontal lobe, behind the forehead, for durations of seconds. But what happens when we try to judge much
longer durations of hours or even days without access to a clock or any clues as to day and night?
THE PERFECT SLEEP
Do glaciers carve their way through caves underground in the same way as they gouge through mountains above the ground? This was the question that the French speleologist Michel Siffre set out to answer when he planned an underground expedition in 1962. But having made his initial arrangements, he began to ponder a quite different question, one which was to revolutionise another field of study entirely.
He would make the trip as planned, taking all the standard equipment such as tents, ropes, lanterns and food, but would leave one item behind – his wristwatch. Instead of recording glacier measurements, he would systematically record his perceptions of time passing. He wanted to explore the natural rhythms of the body untainted by outside cues. The longest attempts to do this had at that point lasted only seven days, with both American and Soviet astronauts taking part in Cold War isolation studies to assess how people might survive in fall-out shelters after a nuclear attack. Michel had done the same, volunteering to spend a week in silent darkness in an experiment at an air force base in Ohio. Now he wanted to try it out for far longer, in more extreme conditions.
The authorities were not keen on letting a 23-year-old embark on such a risky expedition. But Michel was determined and he had form when it came to persuasion, having
convinced a professor at the Academy of Sciences in France to take him on as a geology student when he was only 15. The difference this time was that he was putting his life at risk.
The location Michel had selected for his experiment was the Scarasson Cavern, a cave created from hundreds of horizontal layers of ice, which, unusually for a subterranean glacier, wasn’t linked to a glacier on the surface. To reach the ice cave Michel would need to descend a 130-foot shaft, part of which was S-shaped, meaning that if he were to slip on the ice and break his arm it would be impossible to haul him out; a minor fracture would result in death. Assuming he made it safely down into the cave, he planned to spend
two months
down there in complete isolation. He offered to sign disclaimers, freeing the authorities from any legal responsibility for his safety, but they insisted they would still be morally responsible. He was too young, they told him, too inexperienced, and above all too optimistic. Even after he made a year of detailed preparations, some still maintained the whole idea was nothing but a stunt. The turning point came when he delivered a lecture on his previous expeditions to his friends at the Club Martel potholing group. They saw that he was serious and agreed to act as a support team. Still he would need funding and written permission. He made numerous visits to the offices of officials where he would sit and wait, only to be told after an hour or more that the person in charge was too busy to see him. Michel started to feel these office visits might require more perseverance than the expedition itself.
While he negotiated all the bureaucratic obstacles, Michel
theorised about the experiment he was hoping to carry out on his own mind. He speculated that time existed on three levels: biological time, which stretched across many years; perceived time, created by the brain and conditioned by light and dark; and the objective time as shown on a clock. His interest was in comparing the final two. Specifically he wanted to discover through extreme self-experimentation whether humans have an inner clock that somehow synchs with ‘clock time’ even without any external cues. He also wanted to know how time would
feel
. On past trips underground he had found that time warped. The subterranean world was so absorbing that whenever he returned to the surface he was astonished to discover how much time had passed.
Eventually Michel raised the necessary funds and persuaded the authorities to let him go ahead. Although he would ultimately be all alone in the cavern, during the preparations he had a team of people helping him. For several weeks beforehand his friends from the potholing club stayed with him in his parents’ house, preparing equipment and supplies during the day and sleeping in the hallways at night. Meanwhile Michel had been instructed to rest. The team loaded the equipment onto trucks and drove as near to the cave as they could. When the trucks got snowed in they even built a primitive telefiric railway with a cable and brakes for moving the heaviest items. They marched through the snow for hours at a time carrying the rest of the supplies to the mouth of the cavern. They negotiated the difficult descent and ensured that Michel would have all the equipment and supplies he needed. Once the
underground camp was set up, two of the men spent three nights in the tent as a trial.
Michel said goodbye to his mother. Again she told him how afraid she was. Again he told her how hopeful he felt. He spent the last night before his descent in a tent at base-camp with the idea that he would feel rested before his descent. Instead his fear kept him awake, and when he emerged from his sleeping bag next morning he had slept so little that his bones ached. As he began the climb up to the mouth of the cavern he was struck by an attack of amoebic dysentery. Things weren’t looking good. Still he gave the team strict instructions not to join him underground until two months had passed, signing a statement immediately before his descent, which declared that during the first month no one must attempt to rescue him, whatever the circumstances. Finally he handed over his wristwatch and began his descent with the team. They checked that the tent and camp bed were as he wanted them, taught him how to change the batteries powering the light bulb and the telephone, took some samples of ice from the glacier and then they left. Calls of
‘Au revoir
’ echoed down the chamber. Michel heard them pull the ladders up. Until they came to fetch him in two months he really was alone. Did his mind or body contain a clock that could judge the passage of time, and would he continue to be able to guess when a minute had passed?
Before we return to Michel at the end of his two lonely months, I want to look at the way we assess durations of a few seconds or more, an amount of time that would seem like nothing to Michel, but which surprisingly counts as
long in time-perception research. Warren Meck is a neuroscientist at Duke University in the USA who studies people with a skewed sense of time. By examining the cognitive processes involved in processing durations ranging from seconds to hours, he has localised the perception of time-frames of more than a few seconds to an area at the centre of the brain called the basal ganglia. Until 2001 no one had any idea that these areas housing a mass of neurons could be involved in the perception of time. The basal ganglia, one in each hemisphere of the brain, are deep inside the middle of your head and they loop around in a curve a bit like the older kinds of hearing aid which curl around over the top of the ear. The basal ganglia help control movement using the neurotransmitter dopamine to put brakes on your muscles. If you want to sit down you need to stop the activity in all your muscles, apart from those needed to maintain your sitting position. Then when you want to get up the basal ganglia release the brake on the muscles and that helps you to move off smoothly. Meanwhile a brake is put on those postural movements that were keeping you still. Without enough dopamine to power this brake you would experience both the tremors and jerky movements associated with Parkinson’s disease. You would find it difficult to initiate movement, rather like trying to drive with the handbrake on. But the basal ganglia are also implicated in timing events which last longer than two seconds. This is also something people with Parkinson’s disease find difficult. This condition destroys the cells producing dopamine and the greater the number of cells a person has lost, the harder they find it to estimate time.
The whole dopamine system appears to be crucial in the perception of time. If you give someone the drug haloperidol, often prescribed for schizophrenia, it blocks the receptors for dopamine and causes people to
under
estimate the amount of time that’s passed, while the recreational drugs methamphetamines (or speed) do the opposite; they increase the levels of dopamine circulating in the brain, which causes the brain’s clock to speed up with the result that people then
over
estimate the amount of time that has passed. This might seem somewhat counter-intuitive, but it echoes the process that has been hypothesised to occur when people are in fear for their lives.
EMOTIONAL MOMENTS
The basal ganglia, along with the cerebellum and the frontal lobe, bring to three the areas of the brain we’ve looked at so far. When you consider their other functions, it makes sense that these areas of the brain also relate to time. But the involvement of a fourth area is more mysterious. A psychologist called Bud Craig noticed that whenever people carried out time estimation tasks in a brain scanner, another area kept showing up yet appeared to go unremarked – an area that processes sensations from the rest of the body. He realised that parts of the body
outside
the brain might have a part to play in time perception.
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If it’s very quiet and you lie very still in bed at night, you can sometimes detect your heartbeat, without putting a hand up to your chest. Ten per cent of people can feel their heartbeat at any time, particularly if they’re lean, young
men – it helps to have as little flesh as possible getting in the way. This ability to detect changes in our physiology is known as interoceptive awareness. When I was making a programme about it, I canvassed lots of people to see whether they could do it. None could. As I climbed the many stairs up to my flat I passed the door of the lean young man called Hadley who lives in the flat below. He’s used to my asking strange questions for programmes and when I knocked on his door and asked whether he could hear his own heart beating, he instantly tapped out its rhythm on the table. Now no one is suggesting that we keep time using our heartbeats, but interoceptive awareness could play a part.
The area of the brain that interests Bud Craig is called the anterior insular cortex. It allows us to detect how our body feels and is responsible for gut feelings like disgust, or butterflies in the stomach when you’re in love – those feelings that are mental, yet on the cusp of physical. This would fit in with research on mindfulness, which has found that during mindful meditation people show stronger activity in the insular cortex. We know that people who are deprived of their senses say that time goes slowly. Could the rate of signals coming in through the different senses, including interoceptive awareness, contribute to the creation of our sense of time?