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Cognitive science is usually defined as the scientific study either of mind or of intelligence (e.g. Luger 1994). Practically every formal introduction to cognitive science stresses that it is a highly interdisciplinary research area in which psychology, neuroscience, linguistics, philosophy, computer science, anthropology, and biology are its principal specialized or applied branches. Therefore we may distinguish cognitive studies of either human or animal brains, mind and intelligence.
Even in Ancient Greece philosophers like Plato and Aristotle were interested in understanding the nature of human knowledge. In the seventeenth century Descartes popularized the notion that the body and the mind were two separate entities, Res Extensa and Res Cogitans. Other thinkers on the matter of the mind in the seventeenth and eighteenth centuries included George Berkeley, Robert Burton, Thomas Hobbes, David Hume, Immanuel Kant, and John Locke. In the 1870s, Wilhelm Wundt moved the question of human knowledge into the arena of experimental psychology.
In the early twentieth century, the popular notion of mind was altered by John B. Watson's behaviorist viewpoint that consciousness was not an appropriate question for scientific inquiry and that only observable behavior should be studied. In the 1950s the prevailing viewpoint began to change again as scientists started conceptualizing theories of mind based on complex representations and computational procedures. George Miller pioneered the concept of mental representations, chunks of information that are encoded and decoded within the mind. John McCarthy, Marvin Minsky, Allen Newell, and Herbert Simon founded the field of artificial intelligence around the same time. Noam Chomsky further removed the study of the mind from the behaviorism of Watson, B.F. Skinner, and others that had been psychology's primary focus.
The term cognitive science was coined by Christopher Longuet-Higgins in his 1973 commentary on the Lighthill report, which concerned the then-current state of Artificial Intelligence research. In the same decade, the journal Cognitive Science and the Cognitive Science Society began.
 Principles of Cognitive Science
There are several approaches to the study of cognitive science. These approaches may be classified broadly as symbolic, connectionist, and dynamic systems.
- Symbolic - holds that cognition can be explained using operations on symbols, by means of explicit computational theories and models of mental (but not brain) processes analogous to the workings of a digital computer.
- Connectionist (subsymbolic) - holds that cognition can only be modeled and explained by using artificial neural networks on the level of physical brain properties.
- Dynamic Systems - holds that cognition can be explained by means of a continuous dynamical system in which all the elements are interrelated, like the Watt Governor.
 Levels of analysis
One of the central principles of systemics applied in the symbolic approach to cognitive science is that (1) there are different Levels of Analysis (LOA) from which the brain and mind can be studied, and (2) mental phenomena are best studied from multiple levels of abstraction. For example, these levels are broken into three (not well separated) groups, based on Marr's description of them:
- Computational (Behavioral) level: describes the directly observable output (or behavior) of a system.
- Algorithmic (Functional) level: describes how information is processed to produce the behavioral output.
- Implementational (Physical) level: describes the physical substrate that the system consists of (e.g. the brain; neurons).
A simple analogy often used to describe LOA is to compare the brain to a computer. The physical level would consist of the computer's hardware, the behavioral level represents the computer's software, and the functional level would be the computer's operating system, which allows the software and hardware components to communicate.
Another division of LOA, called specification levels, has been introduced by Gadomski (1993) in the TOGA (Top-down Object-based Goal-oriented Approach) metatheory, where the recognition of the levels is goal-oriented and they are connected by abstract carrier relation (see Computational modeling). From the top perspective, the following initial levels are distinguished: physical, information processing and intelligence. They can be decomposed successively according to arbitrarily assumed criteria of their user/developer.
A central tenet of cognitive science is that a complete understanding of the mind/brain cannot be attained by studying only a single level. For example, consider the problem of remembering a phone number and recalling it later. How does this process occur? One approach would be to study behavior through direct observation. You could present a person with a phone number, ask them to recall it after some delay, and measure their accuracy. Another approach would be to study the firings of individual neurons while a person is trying to remember the phone number. Neither of these experiments on their own would fully explain how the process of remembering a phone number works. Even if we had the technology available to map out every neuron in the brain in real-time, and we knew when each neuron was firing, we still would not know how a particular firing of neurons translates into the observed behavior. Thus we need an understanding of how these two levels relate to each other. This can be provided by a functional level account of the process. By studying a particular phenomenon from multiple levels, we are better able to understand the processes that occur in the brain to give rise to a particular behavior. For criticisms of this framework see Functionalism (psychology).
 Interdisciplinary nature
Cognitive science is an interdisciplinary field with contributors from various fields, including psychology, neuroscience, linguistics, philosophy, computer science, anthropology, biology, and physics. Cognitive science tends to view the world outside the mind much as other sciences do. Thus it too has an objective, observer-independent existence. The field is usually seen as compatible with the physical sciences, and uses the scientific method as well as simulation or modeling, often comparing the output of models with aspects of human behavior. Still, there is much disagreement about the exact relationship between cognitive science and other fields, and the interdisciplinary nature of cognitive science is largely both unrealized and circumscribed.
Many, but not all, who consider themselves cognitive scientists have a functionalist view of the mind—the view that mental states are classified functionally, such that any system that performs the proper function for some mental state is considered to be in that mental state. Thus, according to functionalism about the mind, even non-human systems, such as other animal species, alien life forms, or advanced computers can, in principle, have mental states. This perspective is one of the reasons the term "cognitive science" is not exactly coextensive with neuroscience, psychology, or some combination of the two.
From the external point of view, the largest interdisciplinary context of cognitive science is systemics. It includes the socio-cognitive extension of the cognition models and theories over different social environments social systems, with the emphasis on distributed cognition and intelligence.
 Cognitive science - The term
The term "cognitive" in "cognitive science" is "used for any kind of mental operation or structure that can be studied in precise terms" (Lakoff and Johnson, 1999). This conceptualization is very broad, and should not be confused with how "cognitive" is used in some traditions of analytic philosophy, where "cognitive" has to do only with formal rules and truth conditional semantics. (Nonetheless, that interpretation would bring one close to the historically dominant school of thought within cognitive science on the nature of cognition - that it is essentially symbolic, propositional, and logical.)
The earliest entries for the word "cognitive" in the OED take it to mean roughly pertaining "to the action or process of knowing". The first entry, from 1586, shows the word was at one time used in the context of discussions of Platonic theories of knowledge. Most in cognitive science, however, presumably do not believe their field is the study of anything as certain as the knowledge sought by Plato.
 Scope of cognitive science
Cognitive science is a large field, and covers a wide array of topics on cognition. However, it should be recognized that cognitive science is not equally concerned with every topic that might bear on the nature and operation of the mind or intelligence. Social and cultural factors, emotion, consciousness, animal cognition, comparative and evolutionary approaches are frequently de-emphasized or excluded outright, often based on key philosophical conflicts. Some within the cognitive science community, however, consider these to be vital topics, and advocate the importance of investigating them.
In any way, the essential questions of cognitive science seem to be: What is intelligence? and How is possible to model it computationally?.
Below are some of the main topics that cognitive science is concerned with. This is not an exhaustive list, but is meant to cover the wide range of intelligent behaviors. See List of cognitive science topics for a list of various aspects of the field.
 Artificial intelligence
Main article: Artificial intelligence
"... One major contribution of AI and cognitive science to psychology has been the information processing model of human thinking in which the metaphor of brain-as-computer is taken quite literally. ." AAAI Web pages.
Artificial intelligence (AI) involves the study of cognitive phenomena in machines. One of the practical goals of AI is to implement aspects of human intelligence in computers. Computers are also widely used as a tool with which to study cognitive phenomena. Computational modeling uses simulations to study how human intelligence may be structured. (See the section on computational modeling in the Research Methods section.)
There is some debate in the field as to whether the mind is best viewed as a huge array of small but individually feeble elements (i.e. neurons), or as a collection of higher-level structures such as symbols, schemas, plans, and rules. The former view uses connectionism to study the mind, whereas the latter emphasizes symbolic computations. One way to view the issue is whether it is possible to accurately simulate a human brain on a computer without accurately simulating the neurons that make up the human brain.
Main article: Attention
Attention is the selection of important information. The human mind is bombarded with millions of stimuli and it must have a way of deciding which of this information to process. Attention is sometimes seen as a spotlight, meaning one can only shine the light on a particular set of information. Experiments that support this metaphor include the dichotic listening task (Cherry, 1957) and studies of inattentional blindness (Mack and Rock, 1998). In the dichotic listening task, subjects are bombarded with two different messages, one in each ear, and told to focus on only one of the messages. At the end of the experiment, when asked about the content of the unattended message, subjects cannot report it.
 Language processing
The ability to learn and understand language is an extremely complex process. Language is acquired within the first few years of life, and all humans under normal circumstances are able to acquire language proficiently. Some of the driving research questions in studying how the brain processes language include: (1) To what extent is linguistic knowledge innate or learned?, (2) Why is it more difficult for adults to acquire a second-language than it is for infants to acquire their first-language?, and (3) How are humans able to understand novel sentences they have never heard before?
The study of language processing ranges from the investigation of the sound patterns of speech to the meaning of words and whole sentences. Linguistics often divides language processing into orthography, phonology and phonetics, syntactics, semantics, and pragmatics. Many aspects of language can be studied from each of these components and from their interaction.
The study of language processing in cognitive science is closely tied to the field of linguistics. Linguistics was traditionally studied as a part of the humanities, including studies of history, art and literature. In the last fifty years or so, more and more researchers have studied knowledge and use of language as a cognitive phenomenon, the main problems being how knowledge of language can be acquired and used, and what precisely it consists of. Linguists have found that, while humans form sentences in ways apparently governed by very complex systems, they are remarkably unaware of the rules that govern their own speech. Thus linguists must resort to indirect methods to determine what those rules might be. If speech is indeed governed by rules, they appear to be opaque to any conscious consideration.
A very fecund way to approach cognitive issues in language is the pragmatics of language, that is, the current use of the language by a real speaker. From a pragmatic analytical perspective it is possible to show that some people who have a profession in which they categorically work with language (e.g. journalists) have a behavior which is not predictable by known theories. The pragmatic approach is also useful in the study of collective distributed decision making, particularly in broadcasted systems (for instance aviation approach control - APP).
 Learning and development
Learning and developments are the processes by which we acquire knowledge and information over time. Infants are born with little or no knowledge (depending on how knowledge is defined), yet they rapidly acquire the ability to use language, walk, and recognize people and objects. Research in learning and development aims to explain the mechanisms by which these processes might take place.
A major question in the study of cognitive development is the extent to which certain abilities are innate or learned. This is often framed in terms of the nature versus nurture debate. The nativist view emphasizes that certain features are innate to an organism and are determined by its genetic endowment. The empiricist view, on the other hand, emphasizes that certain abilities are learned from the environment. It is clear that intelligent behavior has components that are both innate and learned, but the extent to which particular behaviors are innate is a major research question. In the area of language acquisition, for example, many questions remain about whether or not a special language acquisition device is necessary to facilitate the learning of language, or if humans can learn language through more general learning processes that take advantage of the information available in the environment.
Main articles: Memory
Memory allows us to store information for later retrieval. Memory is often thought of consisting of both a long-term and short-term store. Long-term memory allows us to store information over prolonged periods (days, weeks, years). We do not yet know the practical limit of long-term memory capacity. Short-term memory allows us to store information over short time scales (seconds or minutes).
Memory is also often grouped into declarative and procedural forms. Declarative memory refers to our memory for facts and specific knowledge (e.g., Who was the first president of the U.S.A.?). Procedural memory allows us to remember actions and motor sequences (e.g. how to ride a bicycle).
 Perception and action
Main article: Perception
Perception is the ability to take in information via the senses, and process it in some way. Vision and hearing are two dominant senses that allow us to perceive the environment. Some questions in the study of visual perception, for example, include: (1) How are we able to recognize objects?, (2) Why do we perceive a continuous visual environment, even though we only see small bits of it at any one time? One tool for studying visual perception is by looking at how people process visual illusions. The image on the right of a Necker cube is an example of a bistable percept, that is, the cube can be interpreted as being oriented in two different directions.
Action is taken to refer to the output of a system. In humans, this is accomplished through motor responses. Spatial planning and movement, speech production, and complex motor movements are all aspects of action.
 Research methods
Many different methodologies are used to study cognitive science. As the field is highly interdisciplinary, research often cuts across multiple areas of study, drawing on research methods from psychology, neuroscience, computer science and systems theory.
 Behavioral experiments
In order to have a description of what constitutes intelligent behavior, one must study behavior itself. This type of research is closely tied to that in cognitive psychology and psychophysics. By measuring behavioral responses to different stimuli, one can understand something about how those stimuli are processed.
- Reaction time. The time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. For example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing.
- Psychophysical responses. Psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. They typically involve making judgments of some physical property, e.g. the loudness of a sound. Correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. Some examples include:
- sameness judgments for colors, tones, textures, etc.
- threshold differences for colors, tones, textures, etc.
- Eye tracking. This methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. The fixation point of the eyes is linked to an individual's focus of attention. Thus, by monitoring eye movements, we can study what information is being processed at a given time. Eye tracking allows us to study cognitive processes on extremely short time scales. Eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed.
 Brain imaging
Brain imaging involves analyzing activity within the brain while performing various cognitive tasks. This allows us to link behavior and brain function to help understand how information is processed. Different types of imaging techniques vary in their temporal (time-based) and spatial (location-based) resolution. Brain imaging is often used in cognitive neuroscience.
- Single photon emission computed tomography and Positron emission tomography. SPECT and PET use radioactive isotopes, which are injected into the subject's bloodstream and taken up by the brain. By observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. PET has similar spatial resolution to fMRI, but it has extremely poor temporal resolution.
- Electroencephalography. EEG measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. This technique has an extremely high temporal resolution, but a relatively poor spatial resolution.
- Functional magnetic resonance imaging. fMRI measures the relative amount of oxygenated blood flowing to different parts of the brain. More oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. This allows us to localize particular functions within different brain regions. fMRI has moderate spatial and temporal resolution.
- Optical imaging. This technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. Since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active (i.e., those that have more oxygenated blood). Optical imaging has moderate temporal resolution, but poor spatial resolution. It also has the advantage that it is extremely safe and can be used to study infants' brains.
- Magnetoencephalography. MEG measures magnetic fields resulting from cortical activity. It is similar to EEG, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in EEG is. MEG uses SQUID sensors to detect tiny magnetic fields.
 Computational modeling
Computational models require a mathematically and logically formal representation of a problem. Computer models are used in the simulation and experimental verification of different specific and general properties of intelligence. Computational modelling can help us to understand the functional organization of a particular cognitive phenomenon.
- Symbolic modeling, is based on the technologies of expert systems or more general Knowledge-Based Systems. They are especially used in information engineering and, recently, in generalized systemics, see for example GOFAI.
- Subsymbolic modeling which includes Connectionist/neural network models. Connectionism relies on the idea that the mind/brain is composed of simple nodes and that the power of the system comes primarily from the existence and manner of connections between the simple nodes. Neural nets are textbook implementations of this approach. Some critics of this approach feel that while these models approach biological reality as a repetition of how the system works, they lack explanative powers as complicated systems of connections with even simple rules are extremely complex and often less interpretable than the system they model.
- Physical Dynamical systems.
All the above approaches tend to be generalized to the form of integrated computational models of a synthetic/abstract intelligence, in order to be applied to the explanation and improvement of individual and social/organizational decision-making.
 Neurobiological methods
Research methods borrowed directly from neuroscience and neuropsychology can also help us to understand aspects of intelligence. These methods allow us to understand how intelligent behavior is implemented in a physical system.
 Key findings
Cognitive science has much to its credit. Among other accomplishments, it has given rise to models of human cognitive bias and risk perception, and has been influential in the development of behavioral finance, part of economics. It has also given rise to a new theory of the philosophy of mathematics, and many theories of artificial intelligence, persuasion and coercion. It has made its presence firmly known in the philosophy of language and epistemology - a modern revival of rationalism - as well as constituting a substantial wing of modern linguistics.
The philosophical underpinnings of research in cognitive science have been continually criticized by philosophers and scientists alike. See Functionalism (Cognitive Science) for an extended entry on this.
 Notable researchers in cognitive science
See the Category of Cognitive Scientists or the list of cognitive scientists
Some of the more recognized names in cognitive science are usually either the most controversial or the most cited. Within philosophy familiar names include Daniel Dennett who writes from a computational systems perspective, John Searle known for his controversial Chinese Room, Jerry Fodor who advocates functionalism, and Douglas Hofstadter. Hofstadter, famous for writing Gödel, Escher, Bach, which questions the nature of words and thought, is Director of the Fluid Analogies Research Group of the Center for Research on Concepts and Cognition at Indiana University. In the realm of linguistics Noam Chomsky and George Lakoff have been influential. Popular names in the discipline of psychology include James McClelland and Steven Pinker.
 See also
- Artificial consciousness
- Cognitive science of mathematics
- Cognitive bias
- Cognitive linguistics
- Cognitive neuropsychology
- Cognitive neuroscience
- Cognitive psychology
- Computational neuroscience
- Educational psychology
- Embodied cognitive science
- Important publications in cognitive science
- List of cognitive scientists
- List of institutions granting degrees in cognitive science
- Neural Darwinism
- Neural network
- Notation bias
- Simulated consciousness
- Society of Mind theory
- SP theory
- Concept Mining
- Baumgartner, P., et. al. Eds. (1995). Speaking Minds: Interviews With Twenty Eminent Cognitive Scientists. Princeton, NJ: Princeton University Press.
- Bechtel, W. et. al. Ed. (1999). A Companion to Cognitive Science. Blackwell Companions to Philosophy. Malden, MA: Blackwell Publishers.
- Damasio, A. R. (1994). Descartes' Error: Emotion, Reason and the Human Brain. New York: Grosset/Putnam.
- Gardner, H. (1985). The Mind's New Science. New York: Basic Books.
- Gazzaniga, M. S. Ed. (1996). Conversations in the Cognitive Neurosciences. New York: The MIT Press.
- Hunt, M. (1982). The Universe Within: A New Science Explores the Human Mind. Brighton: The Harvester Press.
- Lakoff, G and Johnson, M. (1999). Philosophy In The Flesh. New York: Basic Books.
- Luger, G. (1994). Cognitive science : the science of intelligent systems. San Diego: Academic Press.
- Thagard, P. (2nd, 2005). Mind : Introduction to Cognitive Science. Cambridge, MA: The MIT Press.
 Further reading
- Stanford Encyclopedia of Philosophy: Cognitive Science
- Cognitive Science - American Assoc. for Artificial Intelligence
- aiKnow: Cognitive Artificial Intelligence
- MIT CogNet
- Dr. Roy Ruddle's history page at the University of Leeds
- Carl Stahmer's history page at the University of Santa Barbara
- List of People
- Publications & Publishers
- The Journal of Cognitive Science
- The MIT Press
- Indiana Undergraduate Journal of Cognitive Science
 External links
- Indiana Archives of Cognitive Science: An online information portal of everything Cognitive Science
- A special issue of the journal Labyrinthe, 2005 (in French): "La cognition"
- Departments of cognitive science
- CogWiki: a wiki for Cognitive Science
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