Is There an Unconscious Mind or only Unconscious Processes?

1. Unconscious Influences on Cognition

1. Introduction

2. History of the Unconscious

3. Automatic Processing

4. Subliminal Stimuli

5. Priming Effect

6. Blindsight

7. Hypothesis

8. Conclusions

Introduction

Modern psychology and neuroscience routinely operate under the assumption that, apart from the mental processes that we have conscious access to, there are many other brain processes that contribute to our thoughts and behaviors that we cannot consciously access. Some of these unconscious processes are accessible to consciousness but ordinarily go unnoticed, other processes are not accessible to consciousness at all but can be inferred from behavior. An example of the former is when we do something but never examine the preceding thoughts that lead us to do this thing. An example of the latter is when we do something and there are no directly preceding thoughts. Pinpointing unconscious processes and understanding their causes can be very difficult despite the fact that they are ubiquitous and constant. Unconscious processes are thought by most scientists to guide and scaffold not only our physical coordination, but also perception, memory, decision making, motivation and even consciousness itself. All aspects of our behavior, because they are influenced by either innate tendencies or forgotten past experiences, are thought to be affected by unconscious factors.

There are a large number of mental phenomena recognized by cognitive neuroscience as unconscious. Related phenomena include unnoticed emotions, underappreciated motives, subliminal perceptions, unfinished thoughts, hidden phobias, concealed desires, automatic skills, procedural habits and reflexes. A popular example of an unconscious process is the way that people respond to some subliminal messages without being aware of the influence. This is a prototypical example of an unconscious process that most people can relate to. Subliminal messages do not just come from external, environmental stimuli, they also come from within. We will explore a number of such processes, analyze the similarities and differences between them and attempt to create a kind of taxonomy of unconscious phenomena.

We will conclude that behavior is unconscious when neural structures in the brain influence thought or behavior without sharing the full content of their processes globally, making it unavailable to consciousness. I have posited before that when someone becomes conscious of something, prefrontal and parietal association areas, guide the construction of mental representations (usually visual or auditory imagery in sensory areas) of this thing. Therefore, any process that takes place without being recognized by association areas, and subsequently depicted in sensory areas through mental imagery, goes unnoticed and is unconscious.

But this definition is not sufficient to account for all of the various related unconsious phenomena that we will encounter. Because science does not have a thorough definition of consciousness, attempting to delineate unconscious processes proves extremely difficult. Perhaps, though, a thorough definition of unconscious processes will help us define consciousness. In turn, because beliefs cannot be unconscious, this survey into the unconscious will help us to better understand what neurological forms beliefs can and cannot take.

Background

The science of psychology has made tremendous advancements in the past century in its understanding of the unconscious mind and of the automatic processing which underlies it. These advancements have been made in response to a very large amount of evidence that has shown that human behavior is highly influenced by brain procedures that are not recognized by or perceivable to conscious thought. Modern psychological research has thoroughly examined and recorded many observable effects of these unconscious, automatic influences but it has only begun to define the psychological and neurobiological nature of them. Currently the unconscious is viewed by science and philosophy as somewhat enigmatic. Although this chapter does not hope to fully explicate this enigma, it does hope to detail a paradigm for use in analyzing its periphery.

The anthropomorphic, clinically oriented ideas that were established by theorists who initially developed the concept of the unconscious have strongly affected the modern view.  Intellectuals such as Sigmund Freud and Carl Jung personified the unconscious as something that had a mind of its own. Because of the limitations of their day, these theorists were not able to analyze the mind or the unconscious from a rigorously biological perspective. As unconscious processes are primarily biological in origin, this perspective is necessary. British psychologist C. Lloyd Morgan famously stated that “In no case is an animal activity to be interpreted in terms of higher psychological processes, if it can be fairly interpreted in terms of processes which stand lower in the scale of psychological evolution and development.” I believe that Morgan’s canon should similarly be applied to the unconscious. Scientists should avoid anthropomorphizing it unnecessarily.

Some modern neuroscientists, psychologists and philosophers seem to think that all unconscious processes can be attributed to an unconscious mind that itself is a mysterious entity that is highly analogous to the conscious mind. This is probably because some unconscious behaviors such as the unfolding of dreams, the telling quality of free associations and the curious validity to many Freudian slips appear to be guided by an intelligent source. These examples will be framed as the results of brain areas acting autonomously - in intelligent ways - but only because they have been programmed with these simple forms of intelligence through their interaction with the conscious brain areas over the span of many years. Not only have brain areas that act automatically and autonomously been programmed by higher-order brain areas, but they have also been programmed by the environment and thus they contain veridically associated elements of objective reality. The primary visual area by itself is dumb and deaf and practically blind, even to its own visual representations, but because it has been programmed by real visual phenomenon in the environment it has its own form of intelligence in the structure of the representations that it is capable of building. In other words, lower brain areas that serve as slave units to consciousness can create quasi-conscious outcomes when they act on their own. These outcomes, even when they seem to involve intentionality or epiphenomenality are merely phantoms of volitional behavior.  It is only the effects of the complex interactions between brain processes and memory then, that take true unconscious processes and weave them into the apparition of an unconscious mind.

If the cognitive unconscious was not guiding conscious thought, scaffolding it and handing it relevant associations, it could not exist on its own. It is important to mention that even though conscious thought guides the mental imagery that is created, it is painting it with experiences and memories that mostly remain preattentive. Everything implicit in the mental imagery that we create is unconscious, only the aspects of the imagery that we notice and attend to, become conscious. Associations that were made conscious in the past are often not noticed or attended to directly but still “feel” like they are more than implicit simply because we could make them conscious if we attended to them.

It is the position of this author that it is only the conscious mind that engages in elaborate, meaningful analysis and what is thought to be the unconscious is actually a non-thinking byproduct of memory that enables both animals and humans to streamline processing and conserve cognitive and metabolic resources. The unconscious may be programmed in an intelligent way, but is not itself intelligent because it does not have the capacity to deliberate over prolonged time periods. Most of its processes carry to completion quickly and although this facilitates intuition, snap-judgments and loose associations, it obviates dedicated reasoning, extended analysis and algorithmic logic. The high-level conclusion that we are approaching here is that unconscious processes do not involve prolonged, persistent activations of cortex and thus are simpler than those that do because transient activations do not persist long enough to allow the global coactivations necessary for conscious thought.

For over a decade, I have had an urging intuition that consciousness can be reduced to unconscious processes. Finally, I have come to the conclusion that this is true on neurobiological grounds. As discussed in the chapter on the octopus analogy, unconscious perceptions and associations are bottom-up processes that can be activated for a prolonged duration if they are selected by the PFC due to their relevance in goal direction. When a module (brain area responsible for a feature of memory) is activated for more than one cycle of reperception it creates a certain amount of continuity (uninterrupted global persistence) between subsequent thoughts that unconscious processes cannot maintain. In other words, consciousness is simply unconscious, associative processing with the continued activation of some processes (modules or neural assemblies) over successive thoughts (neural oscillations). This feature of continued activation augments associative searches by allowing specific features to be used as function parameters (to serve as coactivates) for more than one .

History of the Unconscious

The concepts of consciousness and unconscious influences originated in antiquity and have been contributed to by many different cultures. Hindu texts known as the Vedas (Alexander, 1990), Shakespeare (Faber, 1970), Paracelsus (Harms, 1967) and western philosophers such as Kierkegaard, Leibniz, Nietzsche and Spinoza have all contributed to the concept of the unconscious. One of the first psychologists to contribute substantially to the concept was Sigmund Freud. Freud was a clinical psychologist whose ideas about personal conflicts and the therapies necessary to treat them had a huge impact on the psychology of his time and continues to influence modern clinical psychologists. One of the most seminal parts of Freudian psychology was his conception of the unconscious (he abandoned the currently unscientific term “subconscious” early on).

Freud proposed that every person came across thoughts that troubled and frustrated them. He believed that people often tried to suppress these unsettling thoughts and ideas and that usually these resided in the unconscious. When these thoughts became active again they most often did so without conscious action or knowledge. These suppressed cognitions, many of which were thought to be formed at a very young age, were related to socially unacceptable ideas or desires, jealousy, guilt, inadequacy and traumatic memories. Unconscious thoughts were not available to introspection but could be “tapped” by the use of dream analysis, free association or verbal slips and then “interpreted” by a therapist trained in psychoanalytic methods. Freud also coined the term preconscious which described thoughts which are currently unconscious though available for recall at anytime. One of his most popular conclusions about the unconscious is that it can be taken to represent a tremendous influence on thought and behavior and that the conscious mind is only the “tip of the iceberg.”

John Searle in the “Rediscovery of the Mind” has written a critique of Freudian unconscious. Here he contends that “unconscious thoughts” are untenable constructs and that for thoughts to exist there must be a thinker. Loftus and Klinger have challenged this argument stating that such a thinker could exist silently, culminating in the idea of a dumb unconscious. In my opinion, if what the unconscious does is taken to constitute thinking it should be on a continuum with conscious thinking where unconscious “thoughts” are more discrete, less reconciled with other thoughts and less lasting in the brain. It certainly would not if we were using the previous definition of thought: cyclical oscillations of information between imagery and association areas.

Contrasting Freud’s view, modern psychology does not hold that the information that lies within the unconscious is necessarily repressed and it does not focus so closely on negative emotions. It simply posits that we do not have access to, notice or understand many of the processes underlying thought and behavior (Kihlstrom 1987). Much of Freud’s work is still valuable to modern psychologists and therapists but psychology has changed much since his time. Much of Freud’s work was based on speculation and observation but today’s psychologists are more apt to favor orientations based around research and experimentation. Freud was opposed by critics claiming that his ideas about the unconscious were not falsifiable or scientific and this criticism still lingers.

Today, most research on unconscious processing is done in the academic tradition of the information processing paradigm and not Freud’s psychodynamic one. Speculative concepts such as the Oedipus and Electra complexes, the death wish and the centrality of libidinous impulses are no longer thought to be useful and instead the cognitive tradition minimizes theoretical assumptions and rests on data-driven, empirical research. Even today though, nonscientists commonly use the concept of the unconscious haphazardly to discuss speculative, mystical or occult phenomena.    

Prior to the ‘70s most formal psychological research failed to address unconscious or automatic processing as a scientific phenomenon. Since the 1970s a great number of psychologists have conducted studies to help define exactly what affect the unconscious mind and its automatic processing have on behavior and mental processes. Subsequent work in the area developed a clear framework that carefully defines automatic processing and delves deeply into its implications on different aspects of psychology. Some see the unconscious mind as a limited metaphor that is not cohesive enough to be thoroughly refined. Neuroscientists are more apt to study unconscious processes than the more literary and psychoanalytic concept of the unconscious mind (Westen, 1998). For example, Timothy Wilson’s idea of an adaptive unconscious describes unconscious processes that are not lowly and simple but that involve more complicated, even goal-directed activities. The modifier, adaptive, holds the connotation that the unconscious has been fine-tuned by evolution to respond to organismal and environmental concerns. Keeping these things in mind we will take a look at a few different forms of unconscious processing in order to better understand how they work.

Unconscious and Automatic Processing

Reminiscent of Freund’s iceberg analogy, scientists today believe that a great deal of human behavior is affected by automatic processing. Automatic processing occurs anytime a person’s behavior is influenced without them being consciously aware of it. This type of processing affects what we like, what we are uncomfortable with, what we are motivated by and how we act. It would seem very difficult at times to distinguish conscious from automatic processes. Experts largely agree though that unconscious, automatic processes can be associated with specific, distinguishing elements (Shiffrin and Schneider 1977). Automatic processes are those that 1) occur outside of awareness; 2) are very efficient in that they require very few cognitive resources and can be completed in parallel with other processes; 3) they are uncontrollable in that they cannot be stopped or inhibited once they have been started and 4) they are never intentional. Finally, consciousness is often assessed with verbal reports whereas completely unconscious processes are unable to be perceived or reported upon verbally (Ericsson and Simon, 1993). Conscious processes are available globally so they can be easily directed toward the areas responsible for language and verbal imagery whereas unconscious processes are localized (decentralized and distributed), have limited outputs to other areas, and information about their content cannot be directed to language areas. Thus, unconscious processes are insular, but at the same time very fast. In fact, the conscious mind is thought to be hundreds of milliseconds behind unconscious processes (Shiffrin and Schneider 1977).

Actions that involve automaticity do not require conscious control to be completed. The ability to learn or acquire these automatic processes though, often requires practice or trial and error. In fact, it is thought that all actions conscious or unconscious involve parallel processing which is found when the conscious and the unconscious are working in unison. Walking, driving a car and many other complex functions that necessitate practice involve such parallel or dual processing. It is now thought that very few, if any, high-order cognitive processes use one or the other exclusively (Bargh 1989, 1994; Zbrodoff and Logan 1986).  Reading is a good example of dual processing because learning how to read takes a great deal of practice yet with time the difficulties involved in phonetics, spelling, and sentence recognition become second nature. After much practice one automatically delegates the technical aspects involved in reading to the unconscious and can concentrate his or her conscious thought on the content of the writing. Studies have shown that many forms of motoric, perceptual and cognitive processing can become highly automatic through extensive practice (Underwood 1974).

Early studies of unconscious processing showed that people can acquire complex procedural knowledge, and use this knowledge to guide behavior without the ability to articulate what the knowledge is. Studies of “artificial grammar” expose people to nonsense words with complex sets of synthetic grammatical rules. Words like “GHAKBT” and “POHBST” would be shown to participants. With practice the participants would be able to discern between new words that were either consistent or inconsistent with the grammatical rules that they learned. They could verbally report on their intuition but were completely unable to articulate what the rules of the artificial grammar were.

Another early interest was the role of automatic processes in stereotype formation. When we encounter a member of a group which has been stereotyped we often automatically activate the group’s stereotype without conscious awareness or rationalization. Once activated, the stereotype can influence how we think about or treat this person without our conscious approval or understanding. Most people have limited ability to notice this effect despite the fact that experimental studies have shown that such implicit stereotypes can profoundly influence a subject’s behavior. As with people who have been influenced by subliminal stimuli, when asked to explain their behavior they often confabulate, making up false explanations for their behavior. Stereotypes can be unconscious beliefs or attitudes that serve as covert biasing signals, held largely in implicit memory and retrieved from it for use.

In a paper entitled “Stereotypes and prejudice: Their automatic and controlled components,” (Devine, 1889) the researcher conducted three studies to examine the differences between automatic and controlled processes involved in prejudice. The study showed that high and low prejudice persons are equally knowledgeable of cultural stereotypes. The researcher used thought listing tasks to gather evidence in support of the idea that it does not take hate, or motivation to activate a stereotype, only an association between two concepts. It is because of our way of neural organization that one can receive information consciously and make quick judgments or quick associations, without having to undergo the previous rationalizations that were necessary to make the initial associations. If a person has never rationalized a reason to be biased against someone of a different group, then the stereotype has no basis in memory and so cannot be automatically activated.

It is not understood whether the unconscious can create new associations; whether it can take one concept, rationalize it and associate it to another without conscious awareness. This makes one wonder whether most associations, within the neural association areas, were at one time rationalized by the conscious. One might find themself trying to hurt someone that they have been consciously jealous of in the past without having to become consciously jealous of them again in the present. This points to the idea that the further an association has been elaborated upon in the past, the more conscious it can be taken to be in the present. The unconscious was programmed with certain motivations in mind, so when we use some of these old automatisms we have to ensure that the motivation or emotion that was there when it was created fits the current scenario, otherwise we might be planning behavior with unintended consequences.

Subliminal Perception

Stimuli that are never perceived by consciousness are able to profoundly affect behavior. This is known as subliminal perception. There are many ways to be exposed unconsciously to outside information without being aware of it.  Information that is available for very brief periods or available among a lot of “noise” can be “hidden” from focused attention but still have access to the mind (Vokey and Read, 1985). Visual stimuli that are flashed on a screen very quickly can enter early visual cortex without being processed sufficiently to reach consciousness. Visual stimuli can also be presented and then masked, thereby interrupting the processing. Auditory stimuli can be subliminal if they are played below an audible volume, masked by other stimuli or recorded backwards. Contrary to superliminal stimuli, these forms of subliminal stimuli are below an individual’s absolute threshold for conscious perception.

 Studies examining subliminal stimuli have shown that emotionally arousing pictures can be flashed on a screen for a duration too short for conscious attention to be directed to them. Nonetheless, early processing areas in the visual cortex begin to perceive this imagery and can send outputs to emotional areas increasing physiological arousal without awareness. The person that witnessed the shocking imagery might report that they feel shocked or uneasy but cannot explain why. Perception without awareness (Ortells, Juan et al, 2002) can influence many different types of behavioral consequences including complex decision making. The next section on the phenomenon of priming discusses the effects of stimuli that are consciously perceived but that affect behavior on an unconscious level because exposure to them has been forgotten.

Priming

Priming, or the implicit memory effect, takes place when superliminal exposure to a stimulus is forgotten about completely but still influences the response to a similar stimulus later. Word-stem completion tests are an excellent example. These demonstrate that if someone is shown a long list of words that includes the word misguided, they will be more likely to use the word when asked later to complete a word starting with the letters mis. Priming works best for stimuli within the same modality. This means that visual priming works best with visual cues and verbal priming with verbal cues. But priming can also occur between modalities (Zurif, 1995). Priming can be perceptual (where tab primes table) or conceptual (where tab primes the word chair). Similarly fox can prime the recollection of the word wolf because of their perceptual resemblance. The word fox can also prime the adjective sly, conceivably because of their semantic or conceptual associations (Matsukawa et al., 2005). Multiple primed concepts have been shown to interact together to prime (or speed up processing of) an associated concept in what has been called context priming. This happens when one reads written text. The grammar and vocabulary of a sentence provide contextual cues for words that occur later in the sentence. These later words are processed more quickly than if they had been read alone (Stanovich & West, 1983).

Lexical decision tasks are interesting tests where participants are asked to quickly indicate whether a set if letters is a word or nonword (e.g., “fishing” versus “lishing”). It takes time and processing resources to determine if the word in known vocabulary. But there is a very easy way to speed this process up. These tests show that priming of a related word can increase reaction time. For example if you are shown the word “nurse” and asked if it is a word or nonword, your reaction would be faster if nurse was preceded by “doctor” than if it was preceded by “butter.” Showing people the word “water,” even minutes before, will speed up their recognition of drink as a valid word. This is interesting because since water activates the word drink, it also must activate many other similar words such as “pool,” “splash” and “wet.” This suggests that past associative linkages between concepts may cause us to have a predilection for activating a related concept without having a conscious rationale. Interestingly, primed concepts have been shown to illogically effect decisions. In fact, completely uninformative, only nominally related stimuli can prime networks that result in illogically biased estimations and decisions and this is known as primed contamination (Chapman & Johnson, 2002).

Priming is thought to occur because the neural networks of closely related representations activate and disinhibit each other. The priming phenomenon is not conscious and is unstoppable, an artifact of neural architecture. There are two types of priming, positive and negative. Positive priming, which can occur even if the stimulus is not seen, speeds up the processing of a stimulus. It is thought to be caused by spreading activation where encountering a stimulus makes the representations of it in memory (and other closely associated representations) more active (Mayr & Buchner, 2007). This increased activity makes it so that a related task can fully activate this representation making it consciously accessible. Negative priming occurs when someone experiences a stimulus and chooses to ignore it. The act of ignoring something that is brought to mind makes it less accessible in the future (Reisberg, 2007). The distractor inhibition model asserts that ignored stimuli are actively inhibited in the brain (Mayr & Buchner, 2007).

Studies of patients with anterograde amnesia due to damage to the medial temporal lobe and hippocampus, show that patients retain the ability for perceptual priming and some abilities related to conceptual priming (Cermak et al., 1985). This indicates that the priming phenomenon is independent of the declarative memory system which is controlled by the medial temporal lobe and hippocampus. In the same way, the polypedal pattern of coactivation described in the last chapter is hippocampal independent. For the most part, the dynamics of activation, coactivation and deactivation are driven by the same neural logic that underlies priming phenomena.

Priming and stimulus repetition improves performance and it also decreases neural processing in the cerebral cortex. Studies utilizing a number of different brain imaging techniques indicate that perceptual priming reduces processing (and the energy expenditure and bloodflow associated with it) in early sensory areas (Wig et al., 2005). This is probably because earlier activation sharpens representational networks reducing the efforts needed to reactivate these networks. Conceptual priming has been linked to reduced blood flow in the prefrontal cortex, indicating that its involvement in the semantic processing of words is reduced by prior exposure (Demb et al., 1995). That a fundamental part of the process of conceptual priming, a largely unconscious phenomenon, takes place in the PFC demonstrates that the involvement of the PFC and other association areas does not ensure attention, awareness or consciousness.

Blindsight

An analysis of the phenomenon of blindsight provides an advanced understanding of
human unconsciousness and also has implications for decision making. Past
experimentation involving blindsight created some of the first scientific evidence for the brain basis of automatic processing. This evidence contradicted the once prevalent notion that
sense perceptions must enter consciousness in order to affect behavior. The human brain contains multiple mechanisms, many of which can function simultaneously, allowing it to perform many complex operations smoothly and efficiently. For instance, there are multiple systems, cortical and subcortical, involved in vision.  

Scientist Lawrence Weiskrantz coined the term blindsight after effectively distinguishing two of our visual systems from one another. Weiskrantz and his group administered sight tests to people who were brain damaged. The subjects were normal except for the fact that the damage that they sustained left them blind in large parts of their visual fields (Ptito & Leh, 2007). When a person damages the visual system on a certain side of their head it produces blindness in the visual field on the opposite side of the body. For example, a person who severely damages their right visual cortex will be blind to everything to the left when they are looking straight ahead.

Weiskrantz and other researchers have found that when an object is placed in an
individual’s blind field (scotoma), they report that they are not able to see it, yet they can reach
for it and grab it with uncanny accuracy. The subjects seem surprised and cannot
explain how they were able locate the object after they began to reach for it. They
were able to grab the object because their efforts were aided by a visual system that
does not interact directly with the conscious mind. The retina in the eye gives rise to two separate pathways in the brain one to the visual cortex and the other to a midbrain area called the superior colliculus. The superior colliculus cannot communicate much with the consciousness because the connections that it makes with the cortex are rigid and inflexible. It does communicate with motor outputs and it gives the motor centers the information needed to reach for an object that it perceives. Individuals with blindsight can perform many tasks in their blind field, like discriminate between an x and and o, distinguish between colors or brightness intervals and other things. The interesting thing is that each patient claims that they could not see anything at all, that they made their guesses randomly and that they expect to perform at chance.

At first, this second pathway to the midbrain seems like a redundancy, but on closer inspection it becomes clear that unconscious processing centers like these take responsibilities from the cortex to free up the cortex’s processing resources. A great deal of our movement and thought is not regulated by the conscious mind. Much of this is processed unconsciously, so that we do not have to think about it, and can let our conscious mind devote its time and energy to the more difficult operations.  After the cortex repeats the same action a number of times, it becomes second nature because other unconscious areas intervene and take over. Many further studies have examined the shift from controlled processes to automatic ones and made note of changes in brain activity. Behavioral data have shown that the tasks became automated after practice and that responses become faster, less variable and more accurate (Jansma et al., 2001).

The action of blindsight does not show that there is an unconscious mind that engages in volitional processing. Rather, it shows that the perception of a visual stimulus can interact with a low level of mechanistic processing to organize movement by triggering reflex memory. The behavior in blindsight is very efficient, is uncontrollable, non-intentional and outside of conscious awareness. A subsequent study (Scharli et al, 2003) has shown that people with normal vision can experience blindsight. The researchers performed experiments on normal subjects to simulate blindsight. They presented a visual target on a computer screen in one of six locations followed by a metacontrast mask.  Even when subjects did not acknowledge the location of a stimulus they nevertheless guessed at its location with above chance accuracy. As in blindsight, they are able to somehow consciously perceive, not the stimuli themselves, but the effects caused by perceptive, subcortical areas.

Because evolution is the gradual process of adding to and refining an organism, we
find that the more complex animals retain many of the fundamental traits of their
ancestors. The visual system that allowed the blindsight subjects to locate the object
in their blind field is in fact an evolutionary remnant from much earlier ancestors.  
Fish, amphibians and reptiles have superior colliculi but do not have a cerebral cortex. Thus frogs, lizards and other reptiles have automatic action systems that enable them to respond to their environment in seemingly informed ways that are actually devoid of conscious analysis. It seems that we can assume that many nonmammalian vertebrates, because they are not in possession of a cerebral cortex, would have almost no insight into their visuomotor abilities. This would be equivalent to the individual with blindsight that cannot verbally report any visual experience whatsoever. If a stimulus were to reach a sensory area, and from there travel, not to cortical association areas, but to motor areas, initiating a movement, this should probably not qualify as a conscious act if the person never became aware, through explanatory mental imagery, of why they performed the movement.

This reptilian visual system is responsible for many movements that are automatic for us. If it (the superior colliculus say) were to be lesioned we would have increased difficulty organizing our automatic eye movements and our responses to visual stimuli – actions that we normally pay no attention to because we take them for granted. Normally deliberative and automatic neural systems work together synchronously and we are not able to distinguish one from the other.  In the case of blindsight though, the damage to the subject’s brain creates a schism between the conscious and the unconscious, which is able to be observed and studied by scientists.  

Unconsciousness, Processing Resources and Habit

Concepts in the brain can become interrelated and they can maintain their closeness even when the reason that they have been paired is no longer able to be recalled by the conscious mind. We do our learning by associating new concepts to old ones, or old concepts to old ones in new ways. Concept pairings that are rationalized or used routinely are often taken as knowledge, beliefs or mental schemas. When we make associations with our conscious mind, the brain changes physically, neuronal pathways between associated nodes become more used and therefore more accessible. I have called this gradual process “implicitization” and this is one way for processes to become unconscious.

The following is an example depicting implicitization: People like to get birthday cards and messages from individuals who they know, even if they do not interact with that person on a regular basis. Upon receiving the birthday card or message the person thinks highly and/or fondly of the sender. In many cases the receiver has made many inferences about birthday messages in the past. Some of these may be along the lines of: “if someone sends me a birthday message they want to continue a long-term friendship with me because it is very likely now that they will send me one next year,” or “someone who wants to send me a card every year values me and is less likely to be trying to manipulate me in the short-term.”  When these rationalizations are made by the conscious mind, the brain forms stronger neural connections between birthday cards and positive emotion. In the future, when the person receives a birthday card, they can skip directly to the overarching association without needing to review past rationalizations. They are able to feel the emotion, connection, happiness or fondness for the person who gave them the card without having to reason through why they should feel this way. The rationale that underpins the feeling is implicit.

I only recently received instruction on a very fundamental rule of spelling. My grandmother recently taught me a well known mnemonic for spelling: “Use I before E except after C.” I had to use this rule many times while typing this exact manuscript. At first, I had to stop and think to remember the mnemonic rhyme to be able to spell the words. After a few usages the spelling became more and more automatic. Finally, by the time that I used this rule in the first sentence of this paragraph, it was second nature, I typed it without having to think about it. This automaticity is not due to an intelligent, unconscious mind that processes in parallel with my conscious, and does half of my thinking for me. This automaticity is due to the organization of neural connections and the way that they cooperate to become a passive resource for conscious thought.

People actually have very little insight into their actions for two main reasons: 1) because we do so many things at a time and 2) because it is hard to notice mistakes or omissions since one can only concentrate on one thing at a time. If one is doing something new it can be very difficult to exhibit proficiency because our processing resources are limited and the procedures involved must be consciously deliberated over because only a small fraction of them flow automatically.  If one is working in an area of expertise however, they may have repeated a procedure so many times that most of the elements involved have been sufficiently attended to at one point that they are now effortless. When I perform repeated statistical analyses composed of several steps or grade dozens of papers using the same rubric, slowly the process becomes less effortful. My mind will have more and more opportunity to wander while I complete the steps as my fingers and eyes are guided by past routine. After a while, and after a high degree of automation I start to wonder how these memories that my repeated actions are creating may reemerge in other future tasks. They could rear themselves to my benefit, or if I am not careful, to my detriment.

Our behavior in any situation can be thought of as mostly a patch-work of different responses that we have in our repertoire that are inflexibly and somewhat arbitrarily applied in our everyday activities. At one point, these behaviors (especially when they were first conceived, thought through or imitated) were open to analysis, insight and change. Over time, the behaviors became closed off to new information, to introspection and even to consciousness. After a behavior or a reaction or a tendency or a frame of mind has been open to consciousness, it transitions toward becoming unconscious. The pathways in the brain become more and more ingrained. The psychological avenues in the brain become more and more familiar to us, more trusted because they have proven effective, or at least not harmful. A temporary solution becomes a tendency, becomes a habit, becomes a way of life.

This automation of learned behaviors can be highly beneficial because it allows us to use our limited processing resources to attend to other, incipient behaviors and allows us to pool together a number of automated activities to accomplish more complex, conglomerated activities. The down side of this is that sometimes we have a tendency to put automated activities together in ways that they were not meant to be combined and this can lead to confused behavior, mistakes and even misinformed thought. We combine these automatisms according to instinct, impulse, intuition and, probably to a more limited extent, reason.

Eventually, we stop questioning entire domains of automatic behavior. For instance, we might stop questioning the shortcut that we take home from work and soon we might stop attempting to learn new routes. We might no longer devise new routes, plan them by looking at a map, or even happen upon them by trial and error.  Pretty soon, overcome with concerns about other options that we have, we stop taking old routes that we used to like altogether. Often times the decision to abandon a formerly favored route is not a particularly “conscious” one at all.  There may have been no specific point in time when you decided to stop taking it and if other concerns become more consuming you may never even realize that you forgot about it.  Abandoning or altogether forgetting certain behaviors, interests or frames-of-mind can happen just as easily. Disuse can inadvertently close up any avenue. As we will discuss later, this process is natural and it is important that much of our behavior, especially the rudimentary stuff, is automated to a degree where we don’t have to think about it anymore. Once we realize that our posture is poor and expend effort to maintain postural adjustments over many days, it may remain good for life without us thinking about it much at all. People can also develop social composure, poise and equanimity and then retain it indefinitely without having to recultivate it. So many things - so many aspects of our very person - can be, like my mother used to tell me, “like riding a bike – once you learn it, it’s always there.”

The fact that we have vast repositories of fixed patterns of action enables us to do all of the complex things we do. Imagine having to think about every movement, every decision in a comprehensive way all the time. Nothing would get done. If your morning routine wasn’t automated to a high degree, you would never get out of the door. If your daily routine wasn’t either, you would be the equivalent of a newborn, hard at work trying to figure everything out – always starting from square one. The main difference between you and your hypothetical clone that has lived its lifetime immobilized in a dark, soundproof vat (and so is mentally equivalent to an infant) is the implicit memories that work together to construct explicit thought. Such a clone would be almost totally functionless even though its brain was working fine. Further, this clone would have such a bereft mental life it would be difficult to deem it conscious. One of the reasons that humans develop to become so complicated behaviorally is because after we are motivated to do a simple thing, we learn from it, automate the actions involved in it and can now perform a more complex activity, that responds to a set of more complicated concerns. This works for physical movements and for mental imagery that we create in our minds eye. By exploring this process on a neurological level we should uncover truths about the mind, the brain and even practical truths about how we should comport ourselves morally, socially and professionally.

So the fact that much of our behavior is a patchwork of inflexible actions is good thing; however, it can be bad if we have little insight into how we are sewing the patches together. But would it be helpful to question our driving route at each and every intersection? When we stop questioning ourselves and the applicability of our actions it is very easy to fall into entrenched routines. After years of driving, heavy traffic or a major obstruction on our favorite route won’t deter us, we are willing to wait it out instead of expending the mental energy and exercising the mental discipline it takes to devise an alternate path. What we think now and how we allowed ourselves to think in the past is going to affect our ability to make decisions in the future. If the thoroughfares that are being employed are not numerous, pertinent or well-functioning, behavioral complexity and functionality can be expected to decline. The less variability we seek, the less new knowledge we procure and the less we try to adjust our behavior to closely account for small variations in our environment the simpler our behavior becomes.  This can be very unfortunate. Animals that are less intelligent than us, never have the chance to reclaim their paths in the same way that we do. Older people as well. As we get older we find that all we are is those circuits, aging makes behavioral tendencies very hard to get out of, very hard to change. However, older people can be less limited than anyone for the fact that they have had the most time to expose themselves to novelty, and if they have done this, we can expect them to have the largest repertoires of automatic behaviors.

This topic has much to do with the unexamined life. Unexamined circumstances are ones which you live your way through, but don’t spend much time questioning or analyzing. It has been said that fools allow a great deal of their life to pass by them without examining it, and also that neurotics spend too much time examining meaningless circumstances without benefiting from it. Surely the subject of animal intelligence and animal knowledge overlaps a good deal with this form of examination. Perhaps animals do consciously know a great deal more than we give them credit for, they just don’t examine it using the “higher-order” criteria the way we do. Game animals may have some general ideas about what a hunter is and how to avoid one, without actually examining the human constructs of hunter, hunted and hunting. Perhaps many animals own the gist of love, affection, sadness, rejection, anticipation and friendliness but it is hard for us to see it because they reflect on them and systemize with them in ways that are not expanded by human knowledge. Perhaps another reason why it is difficult to find evidence of high-order conceptual distinctions in animals is because, even though the animal has made the distinction, it is now implicit, and because it is not linked to language, is more difficult for the animal to demonstrate or be motivated to demonstrate.

A great deal of our tendencies have never been acknowledged by us. A smaller number of our tendencies have been acknowledged once or a few times but will never be acknowledged again. An even smaller number of our tendencies will be acknowledged again sometime in our life. It only seems as if once we acknowledge something, that we will acknowledge it all the time, this is because of the power of implicitization. Once we understand why it is bad to interrupt someone we can inhibit the urge without having to reconsider why from first principles. Also, there is a near infinite number of ways to become aware of our tendencies: considering what others will think, considering if someone will be offended, considering whether we ought to wait for a better opportunity, considering if we have done this thing before, considering whether it would be better to come up with an alternate plan. Just because we are made to reflect on a personal tendency in relation to one such concern doesn’t mean that we are truly aware of it as a whole. Just because we can become aware of an aspect of our behavior does this mean that we are self aware?

We said earlier that processes that do not give rise to mental imagery are unconscious. This would imply that with every behavior we are unconscious of a multitude of things. As we tie our shoes we are rarely conscious of our earliest memories of shoe tying, of the minutiae of the physical movements necessary to manipulate the laces or how we would look to another while doing so. These are all things that our attention could be directed to and that we could build imagery about but usually do not. Subcortical areas of the brain that guide the physical coordination of the fingers to tie laces into a bow cannot share the content of their processes with the parts of the cortex that build imagery. People can form mental representations about these kinds of processes and become aware of them, but only indirectly. In this example they would have to either watch or feel themselves tie the shoe and they would probably have to do it slowly. As mentioned earlier, Sigmund Freud made an important distinction regarding such instances and called thoughts that are not conscious, but available to consciousness, preconscious. Thus with each behavior there is a tremendous number of possible mental representations that we could construct but do not and these represent thoughts that are preconscious. Preconscious concepts are very different from unconscious processes. Unconscious processes, although they also do not reach consciousness are actually taking place in the brain.

When we learn and experience we are constantly making new associations. We bind a number of areas together to create imagery. When we do this, we are conscious of many of the associations but because we are often binding several different features from long-term memory at a time there are too many associations being made for us to keep track of all of them. These associations may resurface later, not because we consciously will them to but because of the neural affinities between the associated memories. Many such associations are implicit in our thoughts. The associations underlying the principles of visual perspective are never explicitly spelled out in most people’s mind despite the fact that the visual system would be lost if it couldn’t rely on them. There are many mundane associations between features that we have never questioned but that influence the conscious imagery that we construct. Even associations that we have been conscious of in the past – where we have glimpsed the causal relationship between two concepts, and supported this association with evidence or rationale – can influence us implicitly. Once the association between two concepts is made firmly enough, we often do not need to recollect either the evidence or the rationale to recall or act on the association. This allows precedence to inform behavior.

Becoming conscious of a distinct association between two things happens when a particular association between two concepts is coactivated with other associations. Together these coactivates create imagery in early sensory areas that depicts some kind of interaction between the associated concepts. This imagery is reappraised by association areas, which maintain the two concepts as coactivates but adds new ones, which are sent back to early sensory areas to create more imagery and so on. In other words, the longer the cortical octopus holds two concepts in its embrace during alternating cycles of imagery and reperception, the more the relationship between those two concepts will become conscious. Ironically, the more closely associated these two concepts come to be, the more their imagined aspects become chunked together and the more the association between them is an implicit assumption in subsequent bouts of coactivation.

Conscious and unconscious processes coexist and complement each other like the ancient symbols, yin and yang. It is difficult to see where one starts and where the other begins. The heart of the yin has a small circle of yang, just as our consciousness is structured around unconsciousness. The dividing line between the two intertwined tear drops can be taken to be awareness, the boundary between liminality and subliminality. In Chinese philosophy the yin force is passive, the yang force is active and it is thought that wise people can distinguish between the two. Finally, according to Chinese theory the interaction of the two determines the destinies of humans and other creatures. The parallels here are memorable and might even be instructive.

Conclusions

We have considered here that perhaps the unconscious is not an entity, separate from consciousness, meant to be anthropomorphized. It is part of our mental tool set, part of the wiring of the brain, involved in the simplification of physical action, memory recall, motivation, and other behavior. This review has allowed us to form some general conclusions about how unconscious or automatic effects operate:

1) It is not necessary to be aware of incoming information for it to affect performance

2) automatic processing, unlike controlled processing, cannot be reported about verbally

3) automatic activity involves activation in an area that is too transient to be noticed or recalled

4) automatic activity involves activation in an area that either does not communicate appreciably to the PFC, or at least the PFC has not been tuned to recognize its communications

5) perhaps conscious activity is generally composed of the same types of processes as unconscious activity, only conscious activity is temporally prolonged 

This discussion of unconscious processes may have a powerful bearing on how beliefs are formed and how they can go wrong. Many of the mistakes of belief formation involve a mix of conscious and unconscious thinking-gone-wrong. The true cognitive factors involved in belief determination may be relatively cognitively impenetrable to many because they involve implicit assumptions that go mostly unnoticed. Certain aspects of belief evaluation probably become automated over time until a point is reached where it is very difficult to have introspective insight into a process that illusorily appears conscious and deliberate. But even early beliefs are probably muddled and disarrayed.

The first beliefs, formed in early childhood, must come about without being scrutinized rationally or explicitly. An infant does not have the capacity to search for justification for its beliefs, a process that probably involves life experience and even proficiency with language. This tells us that, as infants grow older, they probably implicitly maintain some of their criteria (which was never exposed to declarative criticism) for accepting beliefs. Infants certainly form strong expectations and attitudes - two processes that appear very much like beliefs. But how do they do this? Looking at beliefs ontogenetically, blurs the line between beliefs and attitudes. Looking at beliefs from the perspective of unconscious processing, blurs the line between implicit and explicit belief.

The neuroscience or neuropsychology of belief is a contentious topic. Some researchers have argued that beliefs must be represented in the mind by consistent, recognizable patterns of neural activity, whereas others have argued that scientists should not expect there to be a coherent neurological substrate or physical embodiment of a belief. To explore this, we must first concede that although beliefs must be physical phenomena and that different beliefs must share some neurological similarities, they are not unitary. There must be several types of beliefs and to some degree every belief must have a different physical, or neuroanatomical makeup. This literature review has pointed out that there are accepted beliefs, rejected beliefs and beliefs that are in the process of being entertained or tried-out. Such “candidate beliefs,” that might be held in suspended disbelief, would probably have a different basis in the brain than a belief that is firmly entrenched in the psyche. New beliefs are usually more tentative whereas the oldest beliefs are unlikely to be overturned easily because of emotional and implicit factors that are difficult to overcome. The neural “networks” that correspond to personally important, long-held beliefs must involve extensive, wiry masses of neurons and axons that branch out and interact with sensory, language and even subcortical systems. On the other hand, a short-lived belief may only amount to a small number of synaptic changes in temporal or prefrontal cortex.  Because beliefs come in so many different flavors, one would assume that they each must have different neural bases. We certainly wouldn’t expect the following types of beliefs to involve the same neuroanatomical infrastructure: uncertain beliefs, religious beliefs, beliefs about motor praxis, superstitious beliefs, implied beliefs, well-contemplated beliefs, common misconceptions, dogmatic beliefs, iconoclastic beliefs, make-beliefs, self-serving beliefs, self-defeating beliefs, etc. Neuroscience does not nearly seem to be ready to attempt to reduce belief from the mysterious, personal experience that we all know, to the cooperation and interactions of the molecules that build and organize neurons, their circuits and their emergent mental processes.  

We can no longer blame the “malicious” unconscious mind for stereotyping individuals against our wishes. We must blame the reemergence of associations that we made hyperaccessible in the past for this automatic stereotyping.  When we dance we can no longer attribute the complex movements which seem so “natural” yet so intricate to the dexterity of the conscious mind. We should attribute this to the many complex memories for movement that we have created within our brain and spine throughout our lives. The unconscious is not a mind, is not an entity and anthropomorphizing it using human adjectives may be fun but is misleading. Or is it? Is it equally as anthropomorphic to attribute beliefs and other high-order cognitive states to our conscious mind?

When I was very young, the material I read about the unconscious led me to believe that it was a mysterious and intelligent entity that connived and planned with foresight and its own set of goals. After reading the psychological literature about unconscious processes more recently, I have come to see them as inadvertent reflexes, misunderstood impulses, and generally just a side effect of the way memory interacts with consciousness. The unconscious is more a series of discrete, unrelated processes than anything that has the cohesion and sophistication to be comparable to consciousness. To me, this illusion of an unconscious entity dissipated to become no longer a mind, no longer another entity that shares my head. However, another major theme that has emerged in this discourse is the piecemail, fragmentary, irrational, unsystematic, unreliable nature of conscious processes. Many studies have shown that we are just a bundle of instincts and impulses and that there is often very little true continuity even in our conscious lives. These findings along with things like the cohesiveness and meaningfulness of my dreams, my Freudian slips and my intuition has urged me to reconsider. Perhaps if I am going to consider my consciousness to constitute a mind despite the fact that it is insubstantial in many ways, then it is only fair to permit unconsciousness the same nominal privilege. Withholding this distinction from unconsciousness could be considered existential hypocrisy.

How can we pursue distinctions between conscious and unconscious processes if conscious processes are actually composed of unconscious ones as discussed above? Earlier I argued that temporal persistence of unconscious processes creates consciousness. Unconscious, associative linkages are responsible for priming all of the things that come to consciousness and unconscious motivational-neurons in the subcortex decide to keep these things primed. “We” don’t pick and choose our associations or motivations, we can inhibit some, but the rationale for this inhibition was, again, summoned unintentionally by associative networks. Remember, when you coactivate a number of different features, concepts that you could never anticipate, or even summon voluntarily, are invoked.

In his newest book, which I thoroughly recommend, Antonio Damasio argues that people become conscious only when “self comes to mind.” In fact, many scientists and philosophers claim that only when conceptions of self-awareness are brought up are we actually conscious. I find this reasoning questionable. I think that we can be conscious when anything is brought to mind. Can’t we be conscious when we are thinking about a friend, about a political situation or about an interesting philosophical question? I think that consciousness is on a continuum where we can be more or less conscious depending on how active the neocortex is. Proposing that self must come to mind for consciousness to happen is discontinuous. It argues that whenever you think of self you are fully conscious and whenever you do not you are fully unconscious. Perhaps many people feel this way because they know that computers and other simple animals can process information, much like the human mind, but do not have a sense of self-awareness. Because computers and simple animals do not have conceptions of self and because they are not conscious people think that only things with a conception of self can be conscious. This kind of logic is known as a false syllogism which occurs when two correct premises lead to an unfounded conclusion. This is also an example of discontinuous thinking. To me, consciousness is on a continuum, gradational, not black or white. There are many things that humans can do that unconscious computers cannot and these things are quantitatively not qualitatively.

I don’t think that a conception of “self” must come to mind to allow consciousness. In fact, I believe that one may have self come to mind while barely being conscious at all. I think that many conceptions of self, like the ones that someone who is highly inebriated might have, can be very simple, even implicit. Imagine yourself drunk to the point where you will not be able to remember anything the next morning (this is called a blackout). Someone who is awake during an alcohol induced blackout is barely conscious, may not be self-monitoring well, but will still have the capacity to hold conceptions about their self. The lives we lead have ingrained conceptualization of self in us to such a degree that when “self comes to mind” it is often practically a reflex – not a deliberative conscientious process. If self must come to mind for us to be conscious this means that much of the neurotic, egoic thinking I do during the day is conscious but pondering I do about philosophical issues unrelated to self is not. This just doesn’t sound right.

The absence of self in autistic individuals presents another good example. Individuals with autism are thought to have very limited empathy for others. Despite their abilities to systemize and understand many nonsocial features of their environment, neurologically they are poorly equipped to conceive of other selves and they often treat other people as if they were objects. Individuals with autism not only lack the ability to conceptualize other selves but also have a very limited sense their own selves. In other words, self rarely comes to mind in autism but this lack of self-awareness should not make us think of them as any less conscious. This reasoning calls for a revised definition of consciousness.

Personally, I think that anytime someone makes an inference about knowledge or belief, above and beyond the simple perceptions that led to it, then they are conscious. When you are perceiving something directly, and also aware of your perception relative to some other concern, you are conscious. This ability, unlike the self-awareness criterion for consciousness, can be seen on a spectrum where different beings have varying ability to create conceptualizations beyond what they can perceive. Further, this criterion for the extent of consciousness is consistent with what we know about unconscious processes. Unconscious processes take place in the cortex when some areas (often sensory areas) are able to contribute to imagery but are not able to coactivate with association areas. Global, temporally-persisting processes must, by definition, extend beyond perception and when they do they become inferences, knowledge and beliefs.

Types of Conscious / Unconscious Processing

The unconscious allows the conscious mind to skip from conception A to conception C when it used to have to go through B first. A is now sufficient to pull up C by itself and B is habituated to. In most cases B can be recalled declaratively (meaning it is preconscious), but is implicit in the process of moving from A to C. In terms of the octopus we introduced in the last chapter, B is a module that can be left out entirely from the coactivation process and the modules that comprise A can activate module C on their own. Thus, a module becomes implicit, and its features become unconscious, when it is no longer needed - during coactivation with its normal coactivates - to recruit another particular module. In this way, the octopus of consciousness is constantly obviating the need for modules. Even some modules that are used are not noticed. Some modules can only be attentively activated, some must be activated by the environment and others must be activated by a special combination of the two. It is as if the octopus realizes where some of its arms are, but cannot tell in the hurry, where other arms are positioned.

Freud maintained that during our waking lives we are conscious and intermittently affected by unconscious processes.  It seems to me that I am usually unconscious but affected intermittently by conscious thoughts and insights.  The unconscious mind can be summed up to one thing, and that is undeliberated action.

References:

Alexander, C. N. 1990. Growth of Higher Stages of Consciousness: Maharishi's Vedic Psychology of Human Development. C. N. Alexander and E.J. Langer (eds.). Higher Stages of Human Development. Perspectives on Human Growth. New York, Oxford: Oxford University Press

Cermak, L.S.; Talbot, N.; Chandler, K.; Wolbarst, L.R. (1985). "The perceptual priming phenomenon in amnesia". Neuropsychologia 23 (5): 615–622.

Demb, J.B.; Desmond, J.E.; Gabrieli, J.D.E.; Vaidya, CJ; Glover, GH; Gabrieli, JD (1995). "Semantic encoding and retrieval in the left inferior prefrontal cortex: a functional MRI study of task difficulty and process specificity". J. Neurosci 15 (9): 5870–5878.

Devine, Patricia. “Stereotypes and prejudice: Their automatic and controlled components,” Journal of Personality & Social Psychology. Vol 56(1), Jan 1989, pp. 5-18.

Harms, Ernest., Origins of Modern Psychiatry, Thomas 1967 ASIN: B000NR852U, p. 20

Jansma JM, Ramsey N, Slagter H, Kahn R. (2001)  Functional Anatomical Correlates of Controlled and Automatic Processing. Journal of Cognitive Neuroscience, Volume: 13 Number: 6 Page: 730-743.

Matsukawa, Junko; Joan Gay Snodgrass; Glen M. Doniger (2005). "Conceptual versus perceptual priming in incomplete picture identification". Journal of Psycholinguistic Research 34 (6).

Mayr, Susanne; Axel Buchner (2007). "Negative Priming as a Memory Phenomenon: A Review of 20 Years of Negative Priming Research". Journal of Psychology 215 (1): 35. 

Ortells, Juan J; Daza, Maria T; Noguera, Carmen; Carmona, Encarna; fox, Elaine; Abad, Maria J F “Perception without awareness: The qualitative differences approach,” Shohov, Serge P. (Ed). (2002). Advances in psychology research, Vol. 14 (pp. 119-142). Hauppauge, NY, US: Nova Science Publishers, Inc. vi, pp. 243.

Ptito, A. and Leh, S.E. (2007). "Brain Mechanisms of Blindsight.". Article invitée; Neuroscientist 13 (5): 506–18

Reisberg, Daniel: Cognition: Exploring the Science of the Mind (2007), page 255, 517.

Scharli, Heinz; Brugger, P; Regard, M; Mohr, C; Landis, Th, “Localisation of "unseen" visual stimuli: Blindsight in normal observer,” Swiss Journal of Psychology - Schweizerische Zeitschrift fur Psychologie - Revue Suisse de Psychologie. Vol 62(3), Sep 2003, pp. 153.

Stanovich, Keith E.; Richard F. West (1983). "On Priming by a Sentence Context". Journal of Experimental Psychology 112 (1).

Westen, D. (1998). The scientific legacy of Sigmund Freud: Toward a psychodynamically informed psychological science. Psychological Bulletin, 124, 333-371

Wig GS, Grafton ST, Demos KE, Kelley WM. (2005). Reductions in neural activity underlie behavioral components of repetition priming. Nat Neurosci. Sep;8(9):1228-33.

Zurif, E.B. (1995), "Brain Regions of Relevance to Syntactic Processing." in Knowledge of Meaning: An Introduction to Semantic Theory, eds. Richard Larson and Gabriel Segal. MIT Press.