Date on Master's Thesis/Doctoral Dissertation

12-2013

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Psychological and Brain Sciences

Committee Chair

Lyle, Keith B.

Author's Keywords

Memory; Threat; Location; Stimuli; Evolution; Ancestral

Subject

Memory--Psychological aspects; Fear--Psychological aspects; Space perception

Abstract

Humans respond to the presence of threatening stimuli more rapidly than nonthreatening stimuli, a trait that some authors believe humans have been selected for. Based on this finding, it has been proposed that humans should also have superior location memory for threatening stimuli, possibly depending on whether stimuli have ancestral (e.g., snakes) or modern (e.g., guns) ecological relevance. This is herein called the Superior Location Memory for Threatening Stimuli (SLMTS) hypothesis. Some authors believe that humans possess a domain-specific adaptation that gives rise to the hypothesized memory advantage for threatening stimuli. The primary aim of this dissertation is to test the SLMTS hypothesis. Three experiments were performed using stimuli that fully crossed threat level (threatening versus nonthreatening) and ecological relevance (ancestral versus modern). Each experiment included a learning phase, in which subjects responded to threatening or nonthreatening stimuli in various locations, and a subsequent location memory phase. Experiments 1 and 2 tested explicit location memory. Experiment 1 compared recall and recognition tests of conscious location memory. Experiment 2 used a version of the Process Dissociation Procedure to test both conscious and unconscious influences of location memory. Location memory for ancestral nonthreatening, ancestral threatening, and modern threatening stimuli was better than for modern nonthreatening stimuli. These results do not support the SLMTS hypothesis but rather support the general mnemonic principles (GMP) hypothesis, which is that location memory is best for stimuli that are uncommon, arousing, and valenced (either positive or negative). However, Experiment 3 tested implicit location memory and supported the SLMTS hypothesis: Implicit memory was greater for threatening than nonthreatening stimuli. I argue that, taken together, the results of the three experiments do not require the invocation of a specific adaptation for explanatory purposes. Finding support for the GMP hypothesis in Experiments 1 and 2 and the SLMTS hypothesis in Experiment 3 is consistent with a domain-general explanation: Location memory is best for stimuli that are deemed most relevant to the memory system given current circumstances and goals. The relevance of these findings to evolutionary psychological theories of memory is discussed and suggestions for future research are offered.

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