The Big Idea – Consciousness

It’s something that governs our perception of reality and tells us we exist. We all know that we have it, yet scientists are still struggling to pin down exactly what it is...

The room is full of people, yet totally silent. Sitting on cushions, their eyes are closed and their faces expressionless. They look totally absorbed in something – as well they might, for they are attempting to get to grips with one of the most profound mysteries in all science: the nature of consciousness.

As practitioners of Buddhist meditation, they’re using mind-watching techniques that were developed over 2500 years ago by the Indian philosopher Siddhartha Gautama, better known as the Buddha. The aim of these techniques is to turn the conscious mind in on itself and to watch it in action.

According to Buddhists, such introspection can give insights into the nature of the mind, reality and the mystery of consciousness. Such claims usually cut little ice with scientists, yet now highly trained Buddhist monks are joining with them to probe the nature of consciousness. By summoning up mental states while undergoing brain scanning, the monks are opening up a new approach to what researchers call ‘the hard problem’: how does brain activity produce the experience of being conscious?

For something most of us are sure we possess, consciousness has proved amazingly hard to pin down. As early as the 5th century AD the philosopher and Catholic saint Augustine of Hippo identified self-awareness as a key aspect of consciousness when he declared: “I understand that I understand”. It took another 1200 years before the first working definition of consciousness emerged, with the English philosopher John Locke claiming it to be “the perception of what passes in a man’s own mind”. As for how this perception emerged, the 17th-century French philosopher René Descartes used what he regarded as unimpeachable logic to conclude that the conscious mind must surely be made of different stuff from brains and bodies – a distinction now known as Cartesian Dualism. Not until the mid-19th century were scientists able to attempt an assault on the mystery of consciousness. The advent of anaesthetics – in which physical exposure to chemicals like ether triggered unconsciousness – had revealed an intimate connection between the body and mind, flatly contradicting Descartes’ claim. Researchers then set about tackling ‘the hard problem’, seeking to bridge the gulf between the subjective experiences of the mind and the objective study of brain activity.

In the 1860s, Wilhelm Wundt of Heidelberg University – now regarded as the father of experimental psychology – took the first tentative steps, using the ancient technique of introspection, training students to note their conscious response to outside stimuli. Wundt’s research highlighted the importance of understanding ‘qualia’, the subjective experiences we have of the world around us – the ‘redness’ of red, or ‘sweetness’ of sugar. Yet while Wundt worked hard to make his work objective, it was hard to gauge if someone’s experience was the same every time, or matched anyone else’s. He also lacked ways to reliably and objectively measure brain activity that he could correlate with subjective experience.

Wundt’s biggest achievement was convincing leading figures such as influential American psychologist William James that consciousness was a direct outcome of brain activity, and thus worthy of study. The challenge now was to find a way to tackle ‘the hard problem’. The first breakthrough came in 1929, when German neurologist Hans Berger used electrodes placed on the skulls of subjects to measure electrical activity within the brain. Called the electroencephalogram (EEG), it allowed Berger to discover two types of electrical activity, called alpha and beta waves, that seemed to be linked with key aspects of consciousness. Alpha waves oscillated around 10 times a second and appeared to reflect the state of consciousness, becoming fainter during sleep or anaesthesia. Beta waves, on the other hand, were about three times faster, and reflected concentration levels and nonconscious responses like the startle reflex.

Are we running on autopilot?

Berger’s discovery began the study of what are now called neural correlates of consciousness (NCCs): types of brain activity associated with conscious experience. These are now a major focus of research by scientists, many of whom think that the key to understanding consciousness involves them understanding how the brain binds together a host of NCCs into a single, unified whole.

It is a belief spurred on by a surprising discovery made in the 1960s: that we’re consciously aware of only a tiny fraction of what our brains perceive. A team led by American neurologist Benjamin Libet applied very weak stimuli to the skin of patients whose brains had been exposed for neurosurgery. EEG measurements revealed that their brains had detected the stimuli, yet the patients said they felt nothing. It was the same story with stronger stimuli that lasted less than 0.5 seconds – while the brains of the patients detected it, the patients hadn’t consciously felt anything.

Similar findings have since emerged from studies of NCCs like vision and the resulting qualia such as the ‘redness’ of red. Our eyes funnel in information at the rate of around a megabyte per second, yet our consciousness seems to ignore all but a tiny amount of it.

This huge disparity suggests the brain processes a massive amount of sensory input unconsciously, distilling it down before we become aware of it. Such processing must take time to perform – suggesting there must be a time delay between our brains detecting a stimulus and our mind consciously registering it. Attempts to measure this delay have led to perhaps the most startling discoveries yet made into the nature of consciousness.

In 1976, a team of researchers led by the German neurologist Hans Kornhuber decided to set up an experiment that would measure the time delay involved in consciously deciding to move a finger, and actually making the movement. The speed of nerve impulses suggested the time delay would be around 200 milliseconds (ms), similar to that of reflex actions. Yet the delay found was much longer – which was at least consistent with the idea that anything involving the conscious mind involves a lot of processing. However, the researchers also found that the brain activity began around 800ms before people claimed to have consciously decided to move a digit. Earlier this year, researchers at the Bernstein Center for Computational Neuroscience in Berlin, Germany, claimed to have found evidence for an astonishing seven-second gap between brain activity linked to a decision and conscious awareness of that decision.

These findings have disturbing implications for the long-cherished notion of free will, as it suggests our actions are not initiated by our conscious mind, but by the non-conscious brain activity out of our perception. As such, free will maybe limited to our consciously choosing not to act in ways determined by our unconscious mind.

Another perplexing discovery was made in 1979 by Libet and his colleagues during studies of the effect of applying direct stimuli to the brain. Again, common sense suggested only a brief delay should exist between the stimulus and conscious detection – but, once more, the researchers found a substantial delay, of around 500ms. And they found something else: that the brain ‘back-dates’ the conscious response, thus creating the impression there was hardly any delay at all.

All these findings suggest that the brain has developed a host of techniques for binding together sensory inputs from the outside world to give us a conscious model of what’s going on around us.

The theatre of the mind

This notion of consciousness as a model of reality fits in well with the sense we have of our brains creating a kind of mental ‘theatre’. In 1988, the Dutch-born American psychologist Bernard Baars took this idea to create the ‘global workspace’ theory of consciousness (GWT).

According to GWT, conscious processes are those currently in the ‘spotlight’ of mental attention, while others remain out of the spotlight, stored in the memory until needed. Meanwhile, unconscious processes are at work behind the scenes – and also form the audience, reacting to what’s currently in the spotlight. GWT is no mere metaphor. It is based on results now emerging from the biggest breakthrough yet in the objective study of conscious processes – brain-scanning. Techniques such as functional magnetic resonance imaging (fMRI) give researchers detailed, real-time maps of brain activity, allowing it to be related to conscious processes. This has led to an explosion in NCC study, with specific parts of the brain relating to conscious processes. For example, a central region of the brain known as the thalamus appears to be crucial in bringing sensory input into the ‘spotlight’ of conscious attention, while the ventromedial cortex near the front seems to create our sense of life having some sort of purpose.

At the same time, researchers are starting to look again at Wundt’s methods for tackling the notoriously difficult subjective aspect of consciousness. They have been recruiting a group of people with decades of experience of controlling their conscious states and reporting their experience – Buddhist monks. Early results from brain-scan studies of monks suggest their years of practising intensive meditation enables them to produce stable mental states to order, giving researchers the consistency needed for reliable insights into the subjective experience of consciousness. Research teams from Rutgers University in the United States and the French National Centre for Scientific Research in Paris have worked with a Tibetan Buddhist lama who can repeatedly switch mental states to order and hold them for around a minute, giving plenty of time to gather data.

Such a meeting of cutting-edge technology and ancient spiritual practice may lead to new insights into the role of NCCs and our ability to control them. Yet it still fails to address some major mysteries about consciousness. Why do we possess it? What advantages does it confer? And are humans alone in being fully conscious?

One possible explanation lies in the view of consciousness as a means of creating a mental model of reality. Any organism with such a model can do more than merely react to stimuli and pray the response is fast enough to escape predators. It can use the model to foresee threats and opportunities out there in the ‘real world’ – freeing it from the speed limitations of non-conscious reflexes. A conscious creature, in other words, need not stumble around blindly, hoping its reflexes will keep it safe. By binding together non-conscious responses to create even a simple model of reality, a creature possessing some degree of consciousness can avoid getting into tight spots in the first place – giving it a huge evolutionary advantage.

This in turn suggests that asking whether an organism is conscious or not may, in fact, be the wrong question. Rather, consciousness may be a matter of degree – with, say, an insect having a markedly less sophisticated model of reality than a human. As with so many aspects of consciousness, definitive answers are still some way off. Even so, there is growing excitement that scientists are now closing in on the mystery of how 1400g (3lb) of squidgy tissue can endow us with our ineffable but unique sense of self.

STUDYIING CONSCIOUS THOUGHT – TIMELINE

528 BC

Indian philosopher Siddhartha Gautama – aka the Buddha – makes study and control of consciousness the basis of a movement now known as Buddhism.

401 AD

The philosopher and Catholic saint Augustine of Hippo identifies self-awareness as a key aspect of consciousness, declaring: “I understand that I understand”.

1690

In his ‘Essay Concerning Human Understanding’, the English philosopher John Locke defines consciousness as “the perception of what passes in a man’s own mind”.

1874

German psychologist Wilhelm Wundt moves consciousness out of purely philosophical inquiry, and advocates its study via introspection.

1890

Pioneering Harvard University psychologist William James rejects Cartesian Dualism, concluding that consciousness is just a product of brain activity.

1979

American brain scientist Benjamin Libet discovers the half second delay between brain activity and the conscious sense of deciding to act. The brain edits out the delay to keep our conscious experiences in step with reality.

1988

Psychologist Bernard Baars puts forward his ‘global workspace’ theory, according to which consciousness is the process by which normally unconscious processes are said to be brought together on a mental ‘stage’.

1990s – present

Advent of brain-scanning methods such as fMRI prompts huge leap of interest in consciousness by revealing brain activity in unprecedented detail.