Dissociating memory accessibility and precision in forgetting

Abstract

Forgetting involves the loss of information over time; however, we know little about what form this information loss takes. Do memories become less precise over time, or do they instead become less accessible? Here we assessed memory for word–location associations across four days, testing whether forgetting involves losses in precision versus accessibility and whether such losses are modulated by learning a generalizable pattern. We show that forgetting involves losses in memory accessibility with no changes in memory precision. When participants learned a set of related word–location associations that conformed to a general pattern, we saw a strong trade-off; accessibility was enhanced, whereas precision was reduced. However, this trade-off did not appear to be modulated by time or confer a long-term increase in the total amount of information maintained in memory. Our results place theoretical constraints on how models of forgetting and generalization account for time-dependent memory processes.

Protocol registration

The stage 1 protocol for this Registered Report was accepted in principle on 4 June 2019. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.c.4368464.v1.

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Fig. 1: Schematic of the experimental procedure.
Fig. 2: Memory performance by condition.
Fig. 3: Model-derived probability estimates for each type of the subjective memory judgement.
Fig. 4: Kullback–Leibler divergence by condition.

Data availability

All anonymised behavioural data collected via the online task are freely available on the Open Science Framework website (http://osf.io/8mzyc/).

Code availability

All HTML, PHP and MATLAB scripts used to run the experimental task and analyse the data are freely available on the Open Science Framework website (http://osf.io/8mzyc/).

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Acknowledgements

We thank S. Mod, L. Begic, T. Houldridge and T. Maltby for help with collecting the laboratory-based pilot data. A.J.H. is funded by the Wellcome Trust (204277/Z/16/Z) and the Economic and Social Research Council (ES/R007454/1). B.A.R. is funded by a Learning in Machines and Brains Fellowship from the Canadian Institute for Advanced Research and a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada (RGPIN-2014-04947). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

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Contributions

S.C.B., B.A.R. and A.J.H. contributed to research design and provided input on the manuscript. S.C.B. and A.J.H. wrote the manuscript and developed the analysis pipeline. S.C.B. coded the experimental tasks, derived the experimental metrics and implemented the statistical analyses.

Corresponding authors

Correspondence to Sam C. Berens or Aidan J. Horner.

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Competing interests

The authors declare no competing interests.

Additional information

Peer review information Primary Handling Editor: Marike Schiffer.

Supplementary information

Supplementary Information

Supplementary Figures, Supplementary Tables, Supplementary Methods and Supplementary References.

Reporting Summary

Supplementary Software 1

A ZIP archive containing MATLAB functions and R scripts necessary for running each analysis reported in the manuscript and reproducing all the figures. This archive has 5 subdirectories ’#_Dependencies’ (file dependencies), ‘0_PreReg’ (pre-registered analyses), ‘1_Sujective’ (exploratory analyses of subjective report data), ‘2_ExNeither’ (exploratory analysis that excluded ‘Neither responses’), and ‘3_Kld’ (exploratory analyses on Kullback–Leibler divergence statistics).

Supplementary Software 1

A ZIP archive containing all the HTML, JavaScript and PHP files required for running the experimental task on a MySQL enabled webserver. ‘index.php’ is the first page that naïve participants are served.

Supplementary Data 1

A Microsoft Excel Workbook with three different sheets. Sheet 1 (titled ‘ManmadeWords’) lists all the word stimuli in ‘manmade object’ semantic category. Sheet 2 (titled ‘NaturalWords’) lists all the word stimuli in ‘natural object’ semantic category. Sheet 3 (titled ‘MainDataset’) contains all the anonymised data included in the final sample.

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Berens, S.C., Richards, B.A. & Horner, A.J. Dissociating memory accessibility and precision in forgetting. Nat Hum Behav (2020). https://doi.org/10.1038/s41562-020-0888-8

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