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. 2025 Feb;53(2):692-709.
doi: 10.3758/s13421-024-01599-4. Epub 2024 Jul 3.

Effect of levels-of-processing on rates of forgetting

Nan Peng  1 , Robert H Logie  2 , Sergio Della Sala  3
Affiliations

Effect of levels-of-processing on rates of forgetting

Nan Peng et al. Mem Cognit. 2025 Feb.

Abstract

The levels-of-processing (LOP) framework, proposing that deep processing yields superior retention, has provided an important paradigm for memory research and a practical means of improving learning. However, the available levels-of-processing literature focuses on immediate memory performance. It is assumed within the LOP framework that deep processing will lead to slower forgetting than will shallow processing. However, it is unclear whether, or how, the initial level of processing affects the forgetting slopes over longer retention intervals. The present three experiments were designed to explore whether items encoded at qualitatively different LOP are forgotten at different rates. In the first two experiments, depth of processing was manipulated within-participants at encoding under deep and shallow conditions (semantic vs. rhyme judgement in Experiment 1; semantic vs. consonant-vowel pattern decision in Experiment 2). Recognition accuracy (d prime) was measured between-participants immediately after learning and at 30-min, 2-h, and 24-h delays. The third experiment employed a between-participants design, contrasting the rates of forgetting following semantic and phonological (rhyme) processing at immediate, 30-min, 2-h, and 6-h delays. Results from the three experiments consistently demonstrated a large effect size of levels of processing on immediate performance and a medium-to-large level effect size on delayed recognition, but crucially no LOP × delay group interaction. Analysis of the retention curves revealed no significant differences between the slopes of forgetting for deep and shallow processing. These results suggest that the rates of forgetting are independent of the qualitatively distinct encoding operations manipulated by levels of processing.

Keywords: Encoding; Episodic memory; Levels of processing; Long-term forgetting; Recognition.

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Conflict of interest statement

Declarations. Conflicts of interests: The authors have no conflicts of interests to disclose. Ethics approval: Approval was obtained from the School of Philosophy, Psychology and Language Sciences Research Ethics Committee, University of Edinburgh (Ethics approval number: 185-2021/5). All procedures performed in this study were in accordance with the principles of the Declaration of Helsinki. Consent to participate: Informed consent was obtained from all participants included in the study. Consent to publication: Consent for submitting the study results to the journal was obtained from all participants. The listed authors have approved this manuscript for submission.

Figures

Fig. 1
Fig. 1
Experimental procedure of the encoding and retrieval trials in Experiment 1
Fig. 2
Fig. 2
Means and standard errors of d primes at different delays under deep and shallow levels of processing (Experiment 1)
Fig. 3
Fig. 3
Means and standard errors of d primes at different retention intervals under deep and shallow levels of processing (Experiment 2)
Fig. 4
Fig. 4
Means and standard errors of d primes at different retention intervals under deep and shallow levels of processing (Experiment 3)
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