The first article here was published in Cognitive Neuroscience a while back - but in January, 2012, a response was published in Frontiers in Consciousness Research, and the first article was made available online NIH/PubMed public access at that time. This is a bit geeky, but it's some interesting reading.
Citation: Michael S. A. Graziano and Sabine Kastner (2011, Jan 1). Human consciousness and its relationship to social neuroscience: A novel hypothesis. Cognitive Neuroscience, 2(2): 98–113.
Human consciousness and its relationship to social neuroscience: A novel hypothesisRead the whole article - free from PubMed.
Michael S. A. Graziano and Sabine Kastner
Princeton University, Department of Psychology, Green Hall, Princeton NJ 08544
A common modern view of consciousness is that it is an emergent property of the brain, perhaps caused by neuronal complexity, and perhaps with no adaptive value. Exactly what emerges, how it emerges, and from what specific neuronal process, is in debate. One possible explanation of consciousness, proposed here, is that it is a construct of the social perceptual machinery. Humans have specialized neuronal machinery that allows us to be socially intelligent. The primary role for this machinery is to construct models of other people’s minds thereby gaining some ability to predict the behavior of other individuals. In the present hypothesis, awareness is a perceptual reconstruction of attentional state; and the machinery that computes information about other people’s awareness is the same machinery that computes information about our own awareness. The present article brings together a variety of lines of evidence including experiments on the neural basis of social perception, on hemispatial neglect, on the out-of-body experience, on mirror neurons, and on the mechanisms of decision-making, to explore the possibility that awareness is a construct of the social machinery in the brain.
“Men ought to know that from the brain, and from the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs and tears. Through it, in particular, we think, see, hear, and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant…”
~ Hippocrates, Fifth Century, BC.
A common neuroscientific assumption about human consciousness is that it is an emergent property of information processing in the brain. Information is passed through neuronal networks, and by an unknown process consciousness of that information ensues. In such a view, a distinction is drawn between the information represented in the brain, that can be studied physiologically, and the as-yet unexplained property of being conscious of that information. In the present article a novel hypothesis is proposed that differs from these common intuitive notions. The hypothesis is summarized in the following five points.
First, when a person asserts “I am conscious of X,” whatever X may be, whether a color, a tactile sensation, a thought, or an emotion, the assertion depends on some system in the brain that must have computed the information, otherwise the information would be unavailable for report. Not only the information represented by X, visual information or auditory information for example, but also the essence of consciousness itself, the inner feeling attached to X, must be information or we would be unable to say that we have it. In this hypothesis, consciousness is not an emergent property, or a metaphysical emanation, but is itself information computed by an expert system. This first point raises the question of why the brain would contain an expert system that computes consciousness. The question is addressed in the following points.
Second, people routinely compute the state of awareness of other people. A fundamental part of social intelligence is the ability to compute information of the type, “Bill is aware of X.” In the present proposal, the awareness we attribute to another person is our reconstruction of that person’s attention. This social capability to reconstruct other people’s attentional state is probably dependent on a specific network of brain areas that evolved to process social information, though the exact neural instantiation of social intelligence is still in debate.
Third, in the present hypothesis, the same machinery that computes socially relevant information of the type, “Bill is aware of X,” also computes information of the type, “I am aware of X.” When we introspect about our own awareness, or make decisions about the presence or absence of our own awareness of this or that item, we rely on the same circuitry whose expertise is to compute information about other people’s awareness.
Fourth, awareness is best described as a perceptual model. It is not merely a cognitive or semantic proposition about ourselves that we can verbalize. Instead it is a rich informational model that includes, among other computed properties, a spatial structure. A commonly overlooked or entirely ignored component of social perception is spatial localization. Social perception is not merely about constructing a model of the thoughts and emotions of another person, but also about binding those mental attributes to a location. We do not merely reconstruct that Bill believes this, feels that, and is aware of the other, but we perceive those mental attributes as localized within and emanating from Bill. In the present hypothesis, through the use of the social perceptual machinery, we assign the property of awareness to a location within ourselves.
Fifth, because we have more complete and more continuous data on ourselves, the perceptual model of our own awareness is more detailed and closer to detection threshold than our perceptual models of other people’s awareness.
The purpose of the present article is to elaborate on the hypothesis summarized above and to review some existing evidence that is consistent with the hypothesis. None of the evidence discussed in this article is conclusive. Arguably, little conclusive evidence yet exists in the study of consciousness. Yet the evidence suggests some plausibility to the present hypothesis that consciousness is a perception and that the perceptual model is constructed by social circuitry.
The article is organized in the following manner. First the hypothesis is outlined in greater detail (Awareness as a product of social perception). Second, a summary of recent work on the neuronal basis of social perception is provided (Machinery for social perception and cognition). A series of sections then describes results from a variety of areas of study, including hemispatial neglect, cortical attentional processing, aspects of self perception including the out-of-body illusion, mirror neurons as a possible mechanism of social perception, and decision-making as a means of answering questions about one’s own awareness. In each case the evidence is interpreted in light of the present hypothesis. One possible advantage of the present hypothesis is that it may provide a general theoretical basis on which to understand and fit together a great range of otherwise disparate and incompatible data sets.
In a recent article from Frontiers in Consciousness Research, Christian Agrillo and Davide Agrillo offered a response to the above article in terms of near-death-experiences serving as a tool for understanding the link between consciousness and social perception.
Citation: Agrillo, C. and Agrillo, D. (2012, Jan). Near-death experiences as a tool for forming a broader comprehension of the link between consciousness and social perception: commentary on Graziano and Kastner (2011). Frontiers in Consciousness Research, 3:6. doi: 10.3389/fpsyg.2012.00006
Near-death experiences as a tool for forming a broader comprehension of the link between consciousness and social perception: commentary on Graziano and Kastner (2011)
Christian Agrillo(1) and Davide Agrillo(2)1 Department of General Psychology, University of Padova, Padova, Italy2 Faculty of Medicine and Surgery, University of Padova, Padova, Italy
A commentary on Human consciousness and its relationship to social neuroscience: a novel hypothesis by Graziano, M. S. A., and Kastner, S. (2011). Cogn. Neurosci. 2, 98–113.
The nature of human consciousness and its neuroanatomical correlates is one of the most profound issues in the field of neuroscience today. Recently, Graziano and Kastner (2011) put forward the intriguing idea that consciousness is a perception, processed by the same neural network which is involved in social perception. The authors provided a number of interesting lines of evidence to support their view, including experiments on the neural correlates of social perception, on neglect, on mirror neurons, and on the mechanisms of decision-making. They also pointed to the involvement of the temporo-parietal junction (TPJ) in “out-of-body” experiences. In their words: “given that the right TPJ has been implicated so strongly in the social perception of others, this evidence appears to support the hypothesis that the machinery for social perception also builds a perceptual model of one’s own mental experience” (p. 106).
Out-of-body experiences are only one of the recurring features commonly reported within the wider phenomenon known as “near-death experiences” (NDEs). NDEs have been defined as an altered state of consciousness which occurs during an episode of unconsciousness, as a result of a life-threatening condition (Greyson and Stevenson, 1980). Under these circumstances, patients sometimes report perceiving a tunnel, a bright light, deceased relatives, a review of their lives, and out-of-body experiences, in which they describe a feeling of separation from their bodies and the ability to watch themselves from above. Most patients have described NDEs as very pleasant. Extensive changes in personality are often found to occur after an NDE, such as decrease in the fear of death (Greyson, 1983) and decrease of neurotic anxieties (Noyes and Kletti, 1977). However, some reports of unpleasant experiences similar to nightmares have been also described. Although people have wondered whether “good” people have pleasurable experiences and “bad” people have distressing ones, a lack of correlation between apparent life deeds and type of NDE has been reported (Greyson and Bush, 1992). Interestingly the content of NDEs seems similar worldwide, across cultures and all times: NDEs occur about equally to people of both genders and of all ages, educational and socioeconomic levels, spiritual beliefs, religious affiliations, and life experiences (Bush, 2002). The exact incidence of this phenomenon is not known. However, during the last decade, NDEs are likely to occur with increasing frequency because of the improved techniques of resuscitation (van Lommel, 2011).
According to some authors, NDEs are a transcendental state of consciousness, in which the mind and the self-function work independently from the unconscious body (Greyson, 2000; van Lommel et al., 2001). Both biological and psychological interpretations have been suggested, according to which NDEs would be explained by specific altered mental states related to critical healthy conditions (for recent reviews see Facco, 2010; Agrillo, 2011; Mobbs and Watt, 2011; van Lommel, 2011). For instance, it is known that endorphins are released under stress and are known to block pain and to induce feelings of well-being and even intense pleasure. This might be responsible for the positive emotional tone of most NDEs. In addition, cortical disinhibition associated with anoxia has been considered responsible for the perception of a tunnel (Blackmore, 1996). Regardless of the exact reasons underlying these visions, it is undeniable that NDEs may play an important role in the comprehension of human consciousness.
A large body of evidence has indicated that the temporal lobe is involved in mystical and religious experiences, and a recent study has also found altered temporal lobe functioning in patients who have reported NDEs (Britton and Bootzin, 2004). Temporolimbic epilepsy seems to activate elements of NDEs (Durwen and Linke, 1987), with the involvement of the same neuroanatomical regions which Graziano and Kastner (2011) have suggested form an important neural network for consciousness and social perception.
In addition to neuroanatomical correlates, there is another important aspect that should be mentioned. Many studies have shown that patients sometimes report meeting deceased relatives, friends, or unknown human beings during the time in which they seem to be dying. This has been commonly attributed to the person’s expectations or wishes to be reunited with their deceased loved ones at the time of their death. However, if this expectation alone was driving the process, people would presumably recognize the human figures; conversely, most of them are unrecognizable. Several authors have tried to provide an explanation for this incongruence (Agrillo, 2011). It is worth noting that both kinds of vision (familiar and unfamiliar figures) belong to the same category: social stimuli, conspecifics. The deep alteration of consciousness reported in NDEs therefore involves the perception/hallucination of social stimuli, suggesting a potential link between consciousness and social perception.
Interestingly, many people are emotionally close to their pets and hope to be reunited with them after death. Therefore, in accordance with the expectation hypothesis, it would also be reasonable to find a large number of hallucinations of deceased pets (non-social stimuli from an evolutionary perspective). However, Kelly (2001) reported that, among almost 300 cases of NDEs, only two people (∼0.7%) reported seeing their pets. Again, this is theoretically compatible with the idea of common cognitive–neural systems between our consciousness and the perception of social stimuli.
We believe that Graziano and Kastner (2011) have raised an interesting point, and that the machinery that computes information about other people may be the same machinery that computes information about our own awareness: this would explain why the altered state of consciousness which occurs during NDEs may lead to hallucinations of social stimuli, regardless of people’s expectations or wishes.
References (links to most articles available at the site)
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- Mobbs, D., and Watt, C. (2011). There is nothing paranormal about near-death experiences: how neuroscience can explain seeing bright lights, meeting the dead, or being convinced you are one of them. Trends Cogn. Sci. (Regul. Ed.) 15, 447–449.
- Noyes, R., and Kletti, R. (1977). Panoramic memory: a response to the threat of death. Omega (Westport) 8, 181–194.
- van Lommel, P. (2011). Near-death experiences: the experience of the self as real and not as an illusion. Ann. N. Y. Acad. Sci. 1234, 19–28.
- van Lommel, P., van Wees, R., Meyers, V., and Elfferich, I. (2001). Near-death experience in survivors of cardiac arrest. Lancet 358, 2039–2045.