Source of activation confusion model

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SAC (source of activation confusion) is a computational model of memory encoding and retrieval. It has been developed by Lynne M. Reder at Carnegie Mellon University. It shares many commonalities with ACT-R.


SAC specifies a memory representation consisting of a network of both semantic (concept) and perceptual nodes (such as font) and associated episodic (context) nodes. Similar to her husband's (John Anderson) model, ACT-R, the node activations are governed by a set of common computational principles such as spreading activation and the strengthening and decay of activation. However, a unique feature of the SAC model are episode nodes, which are newly formed memory traces that binds the concepts involved with the current experiential context. A recent addition to SAC are assumptions governing the probability of forming an association during encoding. These bindings are affected by working memory resources available.

SAC is considered among a class of dual-process models of memory, since recognition involves two processes: a general familiarity process based on the activation of semantic (concept) nodes and a more specific recollection process based on the activation of episodic (context) nodes. This feature has allowed SAC to model a variety of memory phenomena, such as meta-cognitive (rapid) feeling of knowing judgments, remember-know judgments, the word frequency mirror effect,[1][2] age-related memory loss[3] perceptual fluency, paired associate recognition and cued recall,[4][5] as well as account for implicit and explicit memory tasks without positing an unconscious memory system for priming.


  1. ^ Reder, L. M. et al. (2002). 'A reexamination of stimulus-frequency effects in recognition: Two mirrors for low and high frequency pseudowords. Journal of Experimental Psychology: Learning, Memory, and Cognition, 28, 138-152.
  2. ^ Reder, L. M. et al. (2000). A mechanistic account of the mirror effect for word frequency: A computational model of remember-know judgments in a continuous recognition paradigm. Journal of Experimental Psychology: Learning, Memory, and Cognition, 26, 294-320.
  3. ^ Buchler, N. E. G., & Reder, L. M. (2007). Modeling age related memory deficits: A two-parameter solution. Psychology and Aging, 22(1), 104-121
  4. ^ Reder, L. M., et al. (2007). Retrograde facilitation under midazolam: The role of general and specific interference. Psychonomic Bulletin & Review, 14(2), 261-269.
  5. ^ Buchler, N. G., Light, L., & Reder, L. M. (2008). Memory for items and associations: Distinct representations and processes in associative recognition. Journal of Memory and Language, 59, 183-199.