Examining Event-Related Potential (ERP) correlates of decision bias in recognition memory judgments.

Holger Hill,Sabine Windmann,Alexandra Key

doi:10.1371/journal.pone.0106411

Holger Hill, Sabine Windmann + Show 1 more

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https://doi.org/10.1371/journal.pone.0106411

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Abstract

Memory judgments can be based on accurate memory information or on decision bias (the tendency to report that an event is part of episodic memory when one is in fact unsure). Event related potentials (ERP) correlates are important research tools for elucidating the dynamics underlying memory judgments but so far have been established only for investigations of accurate old/new discrimination. To identify the ERP correlates of bias, and observe how these interact with ERP correlates of memory, we conducted three experiments that manipulated decision bias within participants via instructions during recognition memory tests while their ERPs were recorded. In Experiment 1, the bias manipulation was performed between blocks of trials (automatized bias) and compared to trial-by-trial shifts of bias in accord with an external cue (flexibly controlled bias). In Experiment 2, the bias manipulation was performed at two different levels of accurate old/new discrimination as the memory strength of old (studied) items was varied. In Experiment 3, the bias manipulation was added to another, bottom-up driven manipulation of bias induced via familiarity. In the first two Experiments, and in the low familiarity condition of Experiment 3, we found evidence of an early frontocentral ERP component at 320 ms poststimulus (the FN320) that was sensitive to the manipulation of bias via instruction, with more negative amplitudes indexing more liberal bias. By contrast, later during the trial (500–700 ms poststimulus), bias effects interacted with old/new effects across all three experiments. Results suggest that the decision criterion is typically activated early during recognition memory trials, and is integrated with retrieved memory signals and task-specific processing demands later during the trial. More generally, the findings demonstrate how ERPs can help to specify the dynamics of recognition memory processes under top-down and bottom-up controlled retrieval conditions.

Highlights

Reports about past events and experiences rely on accurate retrieval of stored information in memory, and on subjective decision-making processes, called response biases
There were significant Event related potentials (ERP) old/new effects alongside a three-way interaction showing that the old/new effects were missing in the block condition for the liberal criterion
In Experiment 2, we examined whether the bias manipulation by instruction would affect ERPs differently at two different levels of accurate old/new discrimination, to explore the possibility that criterion setting functions interact with memory retrieval processes

Summary

Introduction

Reports about past events and experiences rely on accurate retrieval of stored information in memory, and on subjective decision-making processes, called response biases. The latter play a role especially when the memory trace is weak or retrieval is difficult so that individuals are unsure, but need to report as in forced choice situations. A growing number of experimental studies have shown that variation in memory decision bias is not merely a nuisance variable that needs to be controlled for, but may itself contain important information about cognitive states, processes, and even traits [7,8,9]. Even illusory memories can be reflected in measures of decision bias [14,15]

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