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Spreading activation is a method for searching associative networks, neural networks, or semantic networks. The search process is initiated by labeling a set of source nodes (e.g. concepts in a semantic network) with weights or "activation" and then iteratively propagating or "spreading" that activation out to other nodes linked to the source nodes. Most often these "weights" are real values that decay as activation propagates through the network. When the weights are discrete this process is often referred to as marker passing. Activation may originate from alternate paths, identified by distinct markers, and terminate when two alternate paths reach the same node. However brain studies show that several different brain areas play an important role in semantic processing.〔Karalyn Patterson, Peter J. Nestor & Timothy T. Rogers: "Where do you know what you know? The representation of semantic knowledge in the human brain" ()〕 Spreading activation models are used in cognitive psychology〔Collins, Allan M.; Loftus, Elizabeth F., "A spreading-activation theory of semantic processing", Psychological Review. 1975 Nov Vol 82(6) 407-428 ()〕〔John R. Anderson. ("A spreading activation theory of memory." ) ''Journal of Verbal Learning and Verbal Behavior'', 1983〕 to model the fan out effect. Spreading activation can also be applied in information retrieval,〔S. Preece, A spreading activation network model for information retrieval. PhD thesis, University of Illinois, Urbana-Champaign, 1981.〕〔Fabio Crestani. "Application of Spreading Activation Techniques in Information Retrieval". ''Artificial Intelligence Review'', 1997〕 by means of a network of nodes representing documents and terms contained in those documents. == Cognitive Psychology == As it relates to cognitive psychology, spreading activation is how the brain moves through an entire network of ideas to retrieve specific information. The spreading activation theory presents the array of concepts within our memory as cognitive units, each consisting of a node and its associated elements or characteristics, all connected together by edges.〔Anderson, John R., "A spreading activation theory of memory", Journal of Verbal Learning and Verbal Behavior 22. 1983 ()〕 A spreading activation network can be represented schematically, in a sort of web diagram with shorter lines between two nodes meaning the ideas are more closely related and will typically be associated more quickly to the original concept.〔Collins, Allan M.; Loftus, Elizabeth F., "A spreading-activation theory of semantic processing", Psychological Review. 1975 Nov Vol 82(6) 407-428 ()〕 When a word (the target) is preceded by an associated word (the prime) in word recognition tasks, participants seem to perform better in the amount of time that it takes them to respond. For instance, subjects respond faster to the word “doctor” when it is preceded by “nurse” than when it is preceded by an unrelated word like “carrot”. This semantic priming effect with words that are close in meaning within the cognitive network has been seen in a wide range of tasks given by experimenters, ranging from sentence verification to lexical decision and naming.〔Chwilla, Dorothee J.; Hagoort, Peter; Brown, C. M., "The mechanism underlying backward priming in a lexical decision task: spreading activation versus semantic matching", The Quarterly Journal of Experimental Psychology, 1998, 51A (3), 531-560 ()〕 As another example, if the original concept is “red” and the concept “vehicles” is primed, they are much more likely to say “fire engine” instead of something unrelated to vehicles, such as “cherries.” If instead “fruits” was primed, they would likely name “cherries” and continue on from there. The activation of pathways in the network has everything to do with how closely linked two concepts are by meaning, as well as how a subject is primed. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spreading activation」の詳細全文を読む スポンサード リンク
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