John F. Kihlstrom

University of California, Berkeley

Paper delivered at the Vienna Conference on Consciousness 2007 organized by the Faculty of Life Sciences at the University of Vienna, October 5, 2007.

 

Link to a précis of the talk, distributed in advance of the conference.

Link to general-interest article on "The Rediscovery of the Unconscious".

Link to other papers on the psychological unconscious.

 

Dammen und Herren, it is a privilege to speak to you today about the nature of unconscious mental life.

My graduate-school mentor, the late Martin T. Orne, was born in Vienna, and both his parents, Frank Orne and Martha Brunner-Orne, were graduates of your medical school, and among the founders of the Austro-American Association of Boston.

My topic, of course, also has strong associations with the University of Vienna: Sigmund Freud, a graduate of this medical school, is commonly credited with the discovery of the unconscious mind. Of course, as Henri Ellenberger, the great historian of psychiatry, has shown, the psychological unconscious has a history long antedating Freud (Ellenberger, 1970). But even so, Ellenberger makes clear that the discovery of the unconscious was in a very real sense set in motion by yet another Vienna graduate of a century earlier: I speak of Franz Anton Mesmer, whose doctrine of animal magnetism evolved into hypnosis as we know it today. I happen to think that Mesmer does not deserve his currently poor reputation (Kihlstrom, 2002), but that is an issue for another time: my task today is to discuss the rediscovery of the unconscious mind by modern psychology.

Let me first make the terms of the discussion clear: We are talking about unconscious mental life. There are many physical and biological processes that, in some sense, proceed unconsciously: the expansion of the universe, the orbiting of planets around the sun, evolution by natural selection, photosynthesis, the machinations of DNA.  The biochemistry of brain activity, which in humans at least gives rise to consciousness, itself goes on unconsciously. Considerations such as this led some Romantic philosophers, such as Edward von Hartmann, to declare that the unconscious pervades the universe. But as my colleague the philosopher John Searle has argued, the term unconscious only makes sense when applied to mental activity as a contrast to consciousness -- which leads us to ask what the hallmark of mental life is.

Here we turn to another son of Vienna, Franz Brentano (1838-1917), who taught here from 1874 to 1895 – and who in fact taught Freud, and happily included him in his "school". Brentano, of course, argued (in Psychology from an Empirical Standpoint, 1874) that intentionality is the mark of the mental: all mental states are intentional in nature, and only mental states are intentional. Put another way, mental states are representational: they are always about something. We don’t think, or feel, or desire in the abstract; rather we think, feel, or desire something.

The nature of intentional states was further explicated by Bertrand Russell – another Vienna connection, if somewhat tangential, through Wittgenstein – in terms of propositional attitudes, which state a relation between a person and some proposition P. These attitudes come in various forms: namely, knowing, feeling, and wanting – Kant’s trilogy of mind (Hilgard, 1980), to which we can add believing. I know that Vienna is in Austria; I believe that Vienna is a beautiful city; I feel honored to have been invited here; and I want to deliver a convincing presentation.

Put in the standard language of cognitive psychology, these representations take the form of percepts, memories, knowledge acquired through learning, and thoughts. In an experiment, subjects perceive words that were presented on a computer screen; they remember words that appeared on a list; they learn a new fact about the world; or they think about some problem they encounter in their environment. Usually, these representations are accessible to consciousness, in that the subjects are aware of what is on their minds. The question for us is whether these same representations can exist outside the scope of phenomenal awareness, and nonetheless influence our ongoing experience, thought, and action.

It is important to frame the question in this way because in contemporary psychology the most popular construal of unconscious mental life is in terms of automaticity (Bargh & Ferguson, 2000). According to this view, some mental processes occur outside the scope of conscious awareness and control. These processes are inevitably evoked by the appearance of certain stimuli, are incorrigibly executed once set in motion, consume little or no cognitive resources, and do not interfere with conscious mental activities. Automatic processes are unconscious in the strict sense that they are not available to phenomenal awareness under any circumstances, and can be known only by inference. The distinction between automatic and controlled processes is not without its problems (Moors & DeHouwer, 2006), but has become widely accepted within psychology, and lately a rather large industry has developed around its application in social psychology (Kihlstrom, 2006).

But the fact that some mental processes can occur unconsciously says nothing about whether the mental representations on which they operate, and which they in turn generate, can be unconscious. Certainly automatic processes can act on what Freud would have called preconscious representations, before focal attention (cathexis) is directed to them. But the representations that they generate are generally thought to be consciously accessible. I may not know how unconscious inferences automatically generate the moon illusion (Kaufman & Rock, 1962; Rock & Kaufman, 1962), but I am certainly aware of the moon when I look at it, and I am aware that the moon looks larger on the horizon than it does at zenith. So the question remains: can we have mental representations -- percepts, memories, thoughts, bits of knowledge – which are themselves unconscious, yet influence our experience, thought, and action nonetheless?

Here the study of implicit memory represents a milestone in our understanding of unconscious mental life. We now know that amnesic patients can show priming effects, in which the presentation of a prime affects processing of a target presented later, even though they cannot consciously remember the prime. Priming effects exemplify what Daniel Schacter (Schacter, 1987) has labeled implicit memory – or the influence of a past event on subsequent experience, thought, or action, in the absence of conscious recollection of that event.

Subsequent research has shown that explicit (conscious) and implicit (unconscious) memory can be dissociated in a wide range of conditions, including the amnesic syndrome associated with damage to the medial temporal lobes or diencephalon, the anterograde and retrograde amnesias associated with electroconvulsive therapy for depression, the anterograde amnesias produced by both general anesthesia administered to surgical patients and conscious sedation in outpatient surgery, dementia, including Alzheimer’s disease, normal aging, posthypnotic amnesia, and the functional amnesias associated with dissociative disorders such as fugue and multiple personality.

Here is a demonstration of the dissociation between explicit and implicit memory in the amnesic syndrome: a profound impairment in free recall and recognition, but spared priming on a fragment-completion task (Warrington & Weiskrantz, 1970; see also Graf, Squire, & Mandler, 1984).

Just as implicit memory refers to the influence of past events that cannot be consciously remembered, so implicit perception refers to the influence of events in the current stimulus environment that cannot be consciously perceived (Kihlstrom, Barnhardt, & Tataryn, 1992). Explicit and implicit perception are dissociated in so-called subliminal perception, where priming effects occur even though the prime is presented at an intensity, or for a duration, that is below the threshold for conscious perception; or when the prime has been masked by another stimulus.

Dissociations between explicit and implicit perception can also be observed in other conditions, including blindsight associated with lesions to the striate cortex (Weiskrantz, 1986), visual neglect resulting from damage to the temporo-parietal area of the brain; prosopagnosia; hypnotic blindness and deafness; and the "hysterical" blindness and deafness observed in cases of conversion disorder. They have also been observed in "preattentive" processing in such paradigms as parafoveal vision and dichotic listening, inattentional blindness (Mack & Rock, 1998), repetition blindness, and the attentional blink. In most of these cases the stimulus is in no sense subliminal, which is why I prefer implicit perception as the more appropriate umbrella term.

Subliminal perception effects are sometimes classified as instances of implicit memory, on the ground that the presentation of the prime occurs before the presentation of the target. But in subliminal perception, the stimulus-onset asynchrony is extremely brief, less than a second, with no intervening distraction, so that the prime is presented in what William James called "the specious present". More important, in implicit memory the subject is aware of the prime when it is presented, but subsequently forgets it; in implicit perception the subject was never aware of the prime at all. On these grounds, priming by stimuli presented during general anesthesia are better counted as instances of implicit perception.

Here is a demonstration of the dissociation between explicit and implicit perception in masked priming, with spared semantic priming in a lexical decision paradigm in the absence of conscious perception (Marcel, 1983).

Apparently, subjects can also learn unconsciously, in the sense that new knowledge acquired through experience can affect their ongoing behavior, without being aware of what they have learned. So, for example, Arthur Reber (A.S. Reber, 1993) has shown that subjects can pick up on the "grammar" by which strings of letters have been arranged, so that they can discriminate between grammatical and ungrammatical letter strings, even though they cannot articulate the grammar itself.

Similar implicit learning effects have been observed in a number of different paradigms, including categorization, the detection of covariation, sequence learning, and the control of complex systems. Again, these effects are sometimes classified as instances of implicit memory, but source amnesia, where subjects are aware of what they know but cannot remember where they have learned it, is a better example of implicit memory. By contrast, subjects in implicit learning remember their learning experiences quite well – they just aren’t consciously aware of what they have learned from them. I prefer to reserve that term for unconscious episodic memory – memory for events embedded in a specific spatiotemporal context. Thus, implicit learning refers to the acquisition of semantic or procedural knowledge.

Here is a demonstration of the dissociation between explicit and implicit learning in neurologically intact subjects: having memorized a set of letter strings generated by a finite-state grammar, subjects are able to discriminate among grammatical and ungrammatical letter strings, despite being unable to identify the grammatical rules themselves (A. S. Reber, 1989).

There is even some evidence of implicit thought – where subjects are influenced by ideas that are not, themselves, properly construed as percepts or memories (Dorfman, Shames, & Kihlstrom, 1996; Kihlstrom, Shames, & Dorfman, 1996).

For example, the late Kenneth Bowers and his colleagues (Bowers, Regehr, Balthazard, & Parker, 1990) showed that subjects could discriminate between problems that were soluble and those that are not, even though they had not actually arrived at the solutions in question.

Similar effects have been observed in both neurological patients and intact subjects making risky choices, and in studies of insight learning.

Bowers concluded that an unconscious representation of the solution influenced subjects’ choice behavior, and I think there is merit in his further suggestion that such "intimations" are related to the intuition phase of creative problem-solving. In this view, the unconscious solution gathers strength during the incubation phase, and emerges fully into consciousness as an insight.

In addition to this evidence for the cognitive unconscious, there are also hints of unconscious emotion and motivation.

David McClelland and his colleagues, for example, claimed that procedures such as the Thematic Apperception Test assessed subjects’ unconscious motives, while personality questionnaires such as Jackson’s Personality Research Form assessed conscious motives (McClelland, Koestner, & Weinberger, 1989).

Viewed from this perspective, the frequently lamented lack of substantial correlation between "projective" and "objective" assessments of motive dispositions counts as a dissociation between explicit and implicit motivation (e.g., Spangler, 1992).

In addition, there is some evidence that explicit and implicit motives are elicited by different kinds of stimuli, and predict performance on different types of tasks.

On the affective side of the ledger, Peter Lang cogently argued that, in principle, every emotional state consists in three components: the subjective feeling, the physiological correlate, and the behavioral response.

If so, then -- at least in principle – we can identify explicit emotion with the subjective feeling state, and implicit emotion with the behavioral and physiological components.  Where physiological or behavioral components of emotion occur in the absence of a feeling state, I think we can rightly speak of a dissociation between explicit and implicit emotion (Kihlstrom, Mulvaney, Tobias, & Tobis, 2000).

Lately, social psychologists such as Anthony Greenwald, Mahzarin Banaji, and their colleagues have introduced the Implicit Association Test, a reaction-time measure intended to reveal prejudices and other attitudes that subjects are not aware of harboring (Greenwald et al., 2002).  

But I think the first experimental evidence for the kind of dissociation I have in mind was provided by Winkielman and his colleagues, who presented "subliminal" (actually masked) pictures of smiling and frowning faces to subjects, in an attempt to prime positive or negative moods (Winkielman, Berridge, & Wilbarger, 2005).  In fact, the subjects' mood-ratings showed no difference between the two conditions.  Nevertheless, the subjects primed with the happy faces drank more of a beverage, and increased their desire and willingness to pay for that beverage, compared to those primed with the sad faces.  Given that mood is related to consummatory behavior, we can say that the subjects showed behavioral expressions of positive emotion, even though they were unaware of any change in their feeling state.  

Although these kinds of findings give sufficient reason for taking unconscious mental life seriously, it has to be said that the evidence in each of these domains is not equally strong. I think that implicit perception and memory have now been established to the satisfaction of all but a few critics (and I think that nothing would convince these dissenters anyway!). Implicit thought is on somewhat softer ground, if only because there have been so few relevant studies. Implicit learning has been explored in the laboratory for more than 40 years, but I think that the dissociation between explicit and implicit learning has not been established with the rigor that characterizes research in the domains of perception and memory.

This holds true for implicit motives, and implicit emotions, as well. For example, the correlations between explicit attitudes measured by rating scales and implicit attitudes measured by the IAT are often quite substantial (at least by the standards of personality research), suggesting that the IAT is more an unobtrusive measure of conscious attitudes that subjects would rather not reveal, than a measure of unconscious attitudes as such.

There is also the matter of the comparative power of unconscious processing. Recently, in both the scientific literature and the popular press, authors have touted the power of unconscious learning and thought – that unconscious learning and automatic processing allow us to solve more complex problems, more efficiently, than is possible consciously (Gladwell, 2005; Wilson, 2002).

In some sense, these claims revive Romantic notions of the power of The Unconscious that were popular in the 19^th century (Hartmann, 1868/1931). But it has to be said that these claims are not well founded in the scientific evidence – if for no other reason than that there are relatively few methodologically adequate comparisons of conscious and unconscious processing. There is every reason to think that unconscious perception is analytically limited, for example. Universities like this one, where an older generation teaches what it knows to a younger one, are ample evidence of the power and importance of conscious, deliberate thinking, and conscious, deliberate learning.

More to the point, the debate over automaticity testifies to the odd situation that consciousness still makes psychologists uncomfortable – the philosopher Own Flanagan calls it conscious shyness (Flanagan, 1992). Partly as a holdover from the bad old days of behaviorism, and partly as a reflection of the functionalist stance that is so popular in the philosophy of mind, psychologists and other cognitive scientists are often reluctant to take consciousness seriously, or even utter the word. Still, we must take care that our acceptance of unconscious mental life does not tilt unnecessarily into a stance of conscious inessentialism or epiphenomenalism.

Beyond mere acceptance that the psychological unconscious is a viable concept after all, the phenomena I’ve described here may offer a new approach to one of the central problems in psychology, cognitive science, and neuroscience – what, following Wittgenstein (there’s that Vienna connection again) we might characterize as the puzzling leap from body to mind: what are the neural substrates of conscious awareness?

We get part of the answer from studies of sleep and dreams, like Prof. Hobson’s (Hobson, Pace-Schott, & Stickgold, 2000), and from studies of general anesthesia. But we will also get part of the answer from comparing the neural correlates of explicit and implicit perception, memory, thought, and the like. The explicit-implicit distinction offers a natural control condition for neuroscientific research: what are the differences, in terms of neural activity, between the conscious and the unconscious influence of percepts and memories. In this way, we may get new insights into precisely what makes conscious percepts, and conscious memories, conscious.

Among these insights, I think, is that the neural correlates of consciousness are going to be as variable as consciousness itself. Conscious recollection has its seat in the hippocampus and the rest of the medial temporal lobe memory system, but conscious (visual) perception has its seat in the striate cortex. Where the neural correlates of consciousness lie may depend precisely on what people are conscious of.

Setting neuroscience aside, the explicit-implicit distinction also gives us some insight into the psychological distinction between conscious and unconscious mental life. Returning to Brentano’s and Russell’s discussion of intentionality, note that each of their examples of a mental state invoke the self, and delineate a kind of ownership between the person and what is going through his or her mind. In linguistic terms, conscious mental states always include some reference to the self as the agent or patient of some action, or the stimulus or experiencer of some state.

Consider the sorts of tasks in which we demonstrate the dissociation between explicit and implicit memory (e.g., Graf, Squire, & Mandler, 1984). First, the subject studies a list of words, including the word paragon. On an explicit memory task, the subject is asked what he or she remembers, and replies, in effect, "I remember" such-and-such an event from the past -- with the emphasis on the first person: "I remember studying this item". But when a subject is asked to complete a word-stem or a fragment, or to identify a word, or to determine whether a letter string is a word, self-reference is missing, or is there in a very different way: "That fragment can be completed with paragon", instead of the more familiar response parachute, or parallel. Whatever is going on in the brain during conscious perception and memory, what is going through the mind is a connection between some mental representation of some object or event, and a mental representation of the self. This link is, I think, missing in instances of unconscious processing (Kihlstrom, 1997).

More than 200 years ago, Immanuel Kant asked whether the notion of unconscious mental states made any sense, and concluded that it does.

But only 100 years ago, writing during the infancy of psychology, William James warned in the Principles that the unconscious was "the sovereign means for believing what one likes in psychology, and of turning what might become a science into a tumbling-ground for whimsies". It is all too easy for us, as psychologists, especially psychologists still living in the shadow of Freud, to tell people what they unconsciously believe, or feel, or want – how could they possibly contradict us? Studies of automatic and controlled processes, and of explicit and implicit perception, memory, and the like, offer a solution to James’ warning, because they offer strict criteria for identifying unconscious mental processes and unconscious mental states – and for tying inferences about subjects’ unconscious mental lives to objective evidence of their behavior in the controlled environment circumstances of the laboratory.

The result is that we can now talk about the unconscious in a scientifically respectable way, and discover its scope and limitations, and seek to identify the neural correlates of consciousness.

That, I think, is a great advance in the science of mental life, and I thank you for the opportunity to share it with you.

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