The impact of threat of shock on memory for threat-irrelevant information: Evidence for a role of reduced semantic organization.

Research into the effects of acute anxiety on episodic memory has produced inconsistent findings, particularly for threat-neutral information. In two experiments, we tested the hypothesis that anxiety induced by threat of shock can interfere with the use of semantic-organizational processes that benefit memory. In Experiment 1, participants viewed and freely recalled two lists of semantically unrelated neutral words, one encoded in a threatening context (threat blocks) and one encoded without threat (safe blocks). As predicted, significantly fewer words were recalled during threat than safe blocks. Moreover, free recall patterns following threat blocks showed lower levels of semantic organization as assessed using a "path length" measurement that considers the semantic distance between pairs of consecutively recalled words. Both effects unexpectedly interacted with block order, such that they primarily reflected improved recall and increased semantic organization from the first to the second block in participants who received the threat block first. Experiment 2 used semantically related word lists to reduce potential impacts of task experience on semantic organization. Free recall was again less accurate and showed longer (less organized) path lengths for threat than safe blocks, and the path length effect no longer interacted with block order. Moreover, threat-induced changes to path lengths emerged as a mediator of the relation between physiological effects of threat (increased skin conductance) and reduced subsequent memory. These data point to semantic control processes as an understudied determinant of when and how acute anxiety impacts episodic memory.