Are there multiple memory systems?

And is one of them specialized for storing and retrieving personality traits?

The evolved architecture of the human mind should be interpenetrated with many functionally specialized systems. This principle applies to memory, as well as to learning, reasoning, concept formation, and so on. From this perspective, there is no such thing as “memory”, conceptualized as a unitary system. Rather, there are many different memory systems, each designed to solve a different kind of adaptive problem.

These systems would be useless in the absence of decision-making procedures that are well-designed for retrieving information from them. This suggests that decision rules should have co-evolved with memory systems: Different decision rules need different search engines, each designed to retrieve the most relevant packets of information from various memory systems. This perspective is discussed and tested in papers below on the “scope hypothesis”, especially the 2002 Klein et al paper in Psychological Review.

Other papers report research suggesting that the human mind contains a system specialized for the storage, retrieval, and acquisition of information about people’s personality traits. A specialized learning mechanism is implicated, and there may be a separate subsystem specialized for acquiring and storing information about the self. For more information, email Stan Klein at UCSB.

Klein, S., Cosmides, L., Tooby, J., & Chance, S. (2002). Decisions and the evolution of memory: Multiple systems, multiple functions. Psychological Review, 109, 306-329.

Reviews neuropsychological and experimental evidence for a distinction between episodic and semantic memory about the self. Argues decision systems had to co-evolve with memory systems; tests the scope hypothesis, an example of this; argues priming is functional, not a byproduct of neural activation

Klein, S. B., Cosmides, L., Tooby, J. & Chance, S. (2001). Priming exceptions: A test of the scope hypothesis in naturalistic trait judgments. Social Cognition, 19, 443-468.

Experiments on scope hypothesis, as discussed in Decisions and the Evolution of Memory, above

Klein, S., Cosmides, L., Gangi, C., Jackson, B., Tooby, J. & Costabile, K. (2009). Evolution and episodic memory: An analysis and demonstration of a social function of episodic recollections. Social Cognition, 27 (2), 283-319.

We quickly form stable summaries of another person’s personality traits (friendly, shy, etc), even based on thin information. Why then retain the episodic memories on which the summaries were based? This paper tests the hypothesis that episodic memories allow trait judgments to be updated by new information. It shows that when a delay makes people functionally amnesic (the trait summaries remain but the episodes are lost) no updating occurs; it also demonstrates the same effect in a person who is amnesic due to brain trauma.

Klein, S., Rozendahl, K., & Cosmides, L. (2002). A social-cognitive neuroscience analysis of the Self. Social Cognition, 20, 104-132.

Reports the case of DB, a patient with brain damage who has intact knowledge of his own personality traits, yet impaired knowledge of those of this daughter, impaired knowledge of other domains of knowledge, and impaired episodic retrieval. Suggests a dissociation within the semantic memory system

Klein, S., Cosmides, L., Costabile, K., & Mei, L. (2002). Is there something special about the self? A neuropsychological case study. Journal of Research in Personality, 36, 490-506.

Reports the case of RJ, an individual with autism, who has acquired accurate knowledge of his own personality traits, yet has not acquired culturally consensual knowledge about other domains of semantic knowledge (animals, foods, tools). Suggests a system specialized not just for storing information about the self, but for acquiring it.

Klein, S., Cosmides, L. & Costabile, K. (2003). Preserved knowledge of self in a case of Alzheimer’ s dementia. Social Cognition, 21(2), 157-165.

Reports case of KR, an individual with severe semantic impairments due to Alzheimer’s dementia. She has accurate knowledge of her personality traits prior to onset (and those of her daughter), but not of her current personality, which has changed. Suggests specialized storage system for personality traits, but that ability to update this store can be impaired.

Klein, S., Cosmides, L., Murray, E. & Tooby, J. (2004) On the acquisition of knowledge about personality traits: Does learning about the self engage different mechanisms than learning about others? Social Cognition22(4), 367-390.

Reports further analysis of RJ, an individual with autism, who has acquired accurate knowledge of his own personality traits, but has failed to acquire accurate knowledge of the personality traits of other members of his family. That acquisition about the self is normal while acquisition about others is impaired, further suggests a system specialized for acquiring knowledge about the self: a domain-specific learning mechanism.

Klein, S., German, T., Cosmides, L. & Gabriel, R. (2004). A theory of autobiographical memory: Necessary components and disorders resulting from their loss. Social Cognition, 22(5), 460-490.

Proposes a theory of how different cognitive mechanisms interact to produce personal memory experiences, and predicts a number of different disorders that would result from the loss of each. Provides a roadmap for discovering new dissociations and syndromes related to self knowledge and memory.

Klein, S. (2005) The cognitive neuroscience of knowing one’s self. In Michael S. Gazzaniga, (Ed.), The New Cognitive Neurosciences, III (pp. 1077-1089). Cambridge, MA: MIT press.