Due to numerous factors, consciousness remains one of the most understudied areas in psychology. First of all, it is really hard to define conscious state, and there is still an on-going debate as to what this state entails. Secondly, how do you measure consciousness? Finally, is our cognitive function affected by whether we process information consciously or unconsciously?
In this post I will try to highlight some major theories and viewpoints on the issue. I will also outline important studies and research on human consciousness.
Theories of consciousness: overview
This view has the most empirical evidence compared to the others, which stems from cognitive neuroscience. The view suggests that the state of consciousness is defined by higher order mental representations of being in a particular mental state. This is in direct contrast to the first-order theories of consciousness, which assume that consciousness is determined solely by mental representation of perceived stimuli; thus, conscious experience of seeing a face is determined by mental representation of face alone. Higher-order theory, however, suggests that this is not enough, and that there also should be a mental representation of being conscious. The basic argument is that no mental state is conscious if one is unaware of being in such mental state.
It is widely assumed that the theory accepts the view that higher-order mental representations depend on neural activity in prefrontal and parietal cortex.
One of the high-order theories is a Recurring Processing theory suggested by Lamme (2006). According to the theory, we process information in two stages. First one is feedforward processing, which rapidly delivers visual information (such as colour, shape etc.) to visual cortex; information may or may reach motor areas (deep feedforward processing), causing unconscious response such as looking. Second stage is recurrent processing, in which information is exchanged between higher and lower areas by the means of feedback connections. Then, conscious reportable experience is possible when this information reaches and activates prefrontal and parietal cortex.
2. Neuronal Global Workspace theory
This theory holds that neurons in prefrontal and parietal cortex form a network (workspace) for conscious processing. This is similar to the higher-order theory - however there is one crucial difference. According to the Workspace theory, such functions as behaviour and ability to perform cognitive tasks depends on activity of this 'conscious' workspace. Higher-order view, by contrast, suggests that ability to perform cognitive tasks mostly depends on first-order mental representations, therefore remaining unaffected by whether information is processed consciously (by the prefrontal and parietal cortex).
3. Information Integration theory
This theory suggests that complex patterns of neurons form a single 'core' system, which allows for a variety of possible informational states being represented. Similarly to the previous theories, the activity of the 'core' is assumed to depend on prefrontal and parietal cortex activity. 'Core' processing is what is defined as conscious processing. Similarly to the higher-order theory, II theory assumes that unconscious processing (outside the 'core') does not necessarily lead to poor task performance. However it lacks complexity - and ability to represent many different possibilities. Therefore, higher-level cognitive tasks, which require context sensitivity, might require awareness.
4. First-order views
The first-order view maintains that conscious awareness is determined by early sensory activity alone, independently of higher-order representations. Thus the crucial difference between the first-order and higher-order view is that the latter predicts that conscious awareness is determined at least in part by prefrontal and parietal activity.
Most first-order theories explain the difference between awareness and unawareness by positing that the latter is associated with weak information or with representations in alternative (e.g. subcortical) sensory pathways. Thus this view suggests that conscious and unconscious processing will have different functional consequences.
Numerous neuroimaging studies have identified activations in prefrontal and parietal cortices in association with conscious awareness. These findings support the higher-order, global workspace and information integration views over the first-order view.
Dual-process model v hierarchical model
There are two ways to account for a change in awareness with constant task performance. One is to assume that the conscious and unconscious processing are two separate channels which contribute to task performance, but which operate independently. Thus, change in processing channel should not affect task performance; such dual-process model can be represented as follows: