We are living in exciting times full of technological innovation and developments. We are in the process of developing driverless cars, using reusable rocket technology to go to space and are making significant improvements in the application of Artificial Intelligence. Despite all these amazing developments, we still know surprisingly little about something that has been with us for as long as humans have existed: consciousness.
Lots of research has been conducted in the past few decades aiming to understand how our consciousness works. It is ironic that we have made such significant progress in other fields of science but are still struggling with the study of consciousness, something we have an abundance of empirical data of. Some scientists say this is due to the fact that consciousness is not suitable for scientific investigations because the very definition of consciousness is not clear. There is no fixed scientific definition of consciousness and it is not easy to obtain one, since consciousness is not observable. However, John Searle in his 1998 paper titled “How to study consciousness scientifically” argued that one must distinguish analytic definitions, which attempt to explain the essence of a concept, from common-sense definitions, that simply clarify what one is talking about. In that sense, the common-sense definition of consciousness “refers to those states of sentience and awareness that begin when we wake up from a dreamless sleep and continue through the day until we fall asleep again”. The definition and understanding of consciousness has undergone a few changes in the past decades and has also split into a few opposing views.
Most of the research conducted on consciousness has been focused on our awareness of visual objects, therefore focusing on visual consciousness. The reason for this is that researchers can easily control what is presented to participants and can afterwards directly ask them for a verbal report of their visual experience. The main limitation with this approach was articulated by cognitive psychologist Victor Lamme: “You cannot know whether you have a conscious experience without resorting to cognitive functions such as attention, memory or inner speech.” Therefore, if a participant fails to report a conscious perception, it might only be due to the failure of his cognitive functions.
However, failure in cognitive functions are not the only issues that could arise when conducting experiments to assess people’s consciousness. In post-decision wagering situations for example, participants make a decision (e.g. whether a displayed object is light or dark blue) and then place a wager.
If the participant’s decision is correct, they earn the amount of money wagered, but if they fail to make the correct decision, they loose their money that they wagered. Common sense dictates that wagers should be bigger and more successful if participants’ conscious awareness is high and wagers should be small and imprecise when conscious awareness is low (e.g. colour blindness).
However, several problems arise when the amount of the wagers are the index by which one measures conscious awareness. First of all, using cash as a medium raises the questions of the personal value that money has to each participant.
While a wealthy participant may be indifferent towards small amounts of money, his betting behaviour will probably differ from one of a participant who is personally living from paycheck to paycheck. Furthermore, a natural human tendency is loss aversion and this tendency definitely impacted the betting strategies of the participants.
Another method for studying consciousness looks at consciousness from a neurobiological standpoint. It has been argued that in order to get a better understanding of consciousness, it is essential to look at what happens in certain brain areas when we obtain behavioral indicators of conscious awareness.
Lamme even argued that we should think of consciousness in neural terms instead of behavioral ones – essentially stating that consciousness is a completely biological and physical feature of the organism rather than some abstract concept.
Lamme focused on visual consciousness and found that when subjects where presented with a visual stimulus it led to an automatic processing of the stimulus at different levels of the visual cortex.
The forward sweep refers to the visual stimulus “travelling” through the visual cortex through successive levels. More specifically, the visual stimulus goes through the primary visual cortex, the V1, which receives the sensory inputs from the thalamus and goes through the secondary visual cortex, known as V2, which is the second major area of the visual cortex. You can imagine this forward sweep as a tennis ball which is being thrown vertically into the air.
This process takes about 100-150 milliseconds. After the forward sweep, the recurrent processing starts. Recurrent processing basically involves the feedback from the higher to the lower areas, enabling strong interactions between these different areas. Essentially, recurrent processing is the tennis ball falling back into your hands due to gravity.
The cognitive psychologists Lamme, Fahrenfort and Scholte in 2007 observed that conscious experience seemed to be directly linked to recurrent processing. They set up an experiment taking advantage of the masking effect.
The masking effect basically states that when a first visual stimulus is followed by a second visual stimulus, the second one prevents the conscious perception of the first. Lamme, Fahrenfort and Scholte asked subjects to indicate whether a given target figure (e.g. a specific coloured circle) had been presented or not. The subjects were exposed to both masked and unmasked conditions, meaning that in some of the cases, a second visual stimulus appeared right after the first one. During the entire experiment the subjects brain activity was recorded by placing electrodes on their scalps to measure the electrical activity of the brain.
The Electroencephalogram (EEG) findings showed that there was no evidence of recurrent processing in the masked condition, meaning that when subjects were not consciously aware of the target stimulus there was also no recurrent processing going on in their visual cortex.
Additionally, in 1999 several researchers obtained similar results that underlined the importance of recurrent processing in being consciously aware.
Corthout et. al used a special kind of magnetic stimulation (known as TMS) to briefly disrupt the functions of the primary visual cortex (V1) through magnetic pulses at different times after presenting the subjects to the visual stimulus. Their findings showed that the conscious perception of the stimulus was eliminated when the TMS was applied around 100 milliseconds after the presentation of the stimulus, whereas conscious perception did not change when the TMS was applied less than 80 milliseconds after the stimulation.
Since the recurrent processing starts at around 100 milliseconds after stimulus presentation, when conscious perception was eliminated, the magnetic impulses disturbed the recurrent processing. On the other hand, applying the magnetic impulses before 80 milliseconds implies that only the feedforward sweep would be disrupted which, it seems, did not have any effect on conscious perception. Therefore, this experiment underlines the hypothesis that recurrent processing is required for conscious perception.
These experiments and their findings are making several scientists believe that we must change the way we think about consciousness. Rather than being some abstract concept, it should be seen as a physical process just like digestion or photosynthesis.
Understanding consciousness is a particularly complex endeavour as it requires significant knowledge in several areas such as biopsychology, neuroscience, philosophy and partly artificial intelligence.
A breakthrough in this area would bring us significantly closer to understanding the human brain and to understand the cause-effect relationship of our species. While research in this area is very important, it could bring about several philosophical issues related to free will and the concept of determinism.
Several studies have already shown that for certain actions, our body is already carrying out neurochemical processes before we even make the conscious decision to carry out the action. Therefore, our future findings in the field of consciousness will be vital to understand the real control we have over our actions.