Editing Semantic memory (section)

====ACT-R: a production system model====
The adaptive control of thought (ACT)<ref>Anderson, J. R. (1983). ''The Architecture of Cognition''. Cambridge, MA: Harvard University Press.</ref> (and later [[ACT-R]] (Adaptive Control of Thought-Rational)<ref>Anderson, J. R. (1993b). ''Rules of the mind''. Hillsdale, NJ: Erlbaum.</ref>) theory of cognition represents [[declarative memory]] (of which semantic memory is a part) as "chunks", which consist of a label, a set of defined relationships to other chunks (e.g., "this is a _", or "this has a _"), and any number of chunk-specific properties. Chunks can be mapped as a semantic network, given that each node is a chunk with its unique properties, and each link is the chunk's relationship to another chunk. In ACT, a chunk's activation decreases as a function of the time from when the chunk was created, and increases with the number of times the chunk has been retrieved from memory. Chunks can also receive activation from [[Gaussian noise]] and from their similarity to other chunks. For example, if ''chicken'' is used as a retrieval cue, ''canary'' will receive activation by virtue of its similarity to the cue. When retrieving items from memory, ACT looks at the most active chunk in memory; if it is above threshold, it is retrieved; otherwise an "error of omission" has occurred and the item has been forgotten. There is also retrieval latency, which varies inversely with the amount by which the activation of the retrieved chunk exceeds the retrieval threshold. This latency is used to measure the response time of the ACT model and compare it to human performance.<ref>{{cite journal | last1 = Anderson | first1 = J. R. | last2 = Bothell | first2 = D. | last3 = Lebiere | first3 = C. | last4 = Matessa | first4 = M. | year = 1998 | title = An integrated theory of list memory | journal = Journal of Memory and Language | volume = 38 | issue = 4| pages = 341–380 | doi=10.1006/jmla.1997.2553| citeseerx = 10.1.1.132.7920 | s2cid = 14462252 }}</ref>