A novel study: hypermnesia for books read years ago

ABSTRACT

Memory can increase across repeated tests without any further study, a finding known as hypermnesia (e.g., Erdelyi, M. H., & Kleinbard, J. (1978). Has Ebbinghaus decayed with time? The growth of recall (hypermnesia) over days. Journal of Experimental Psychology: Human Learning and Memory, 4(4), 275–289). This study is the first to examine hypermnesia in a recognition test over long delays between learning and test. The current experiment examined hypermnesia for popular novels across retention spans of up to 10 years. Participants took two tests separated by 24 hours on a novel they had previously read. The tests had identical questions presented in a different order. We found hypermnesia across the recognition tests, which was due to within-test memory improvements. Hypermnesia decreased as a function of retention time due to increased item losses at longer delays. We propose a guessing hypothesis to account for this result and suggest that increased item losses are in part due to greater instability of memory at longer intervals.

KEYWORDS:

• hypermnesia
• memory
• recognition memory
• forgetting

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 The cumulative recall hypothesis suggests that the magnitude of hypermnesia is related to the cumulative level of recall across multiple tests, and that hypermnesia is a result of longer retrieval time (Roediger et al., 1982). As such, this hypothesis applies to tests that are close in time, within minutes of one another. Because of this, the cumulative retrieval hypothesis is not be applicable for our study, in which tests are separated by 24 hours. Furthermore, this hypothesis applies to studies which implement recall to test memory. We do provide a consideration of the asymptotic retrieval principle that focuses exclusively on retrieval levels. The retrieval strategy hypothesis suggests that each retrieval attempt improves the strategies used to organize retrieval, resulting in more efficient recall on subsequent tests and fewer item losses between tests (e.g., Mulligan, 2001). Because this hypothesis is applicable for free recall, but not recognition, this hypothesis is not considered further here.

2 Average response time was 7.5 seconds (SE = .21 seconds). One person had unusually low response times, but their inclusion did not influence the pattern of results, so we elected to keep them in the analysis.

3 This information was collected for thoroughness should it be of interest for future research, but responses to these questions are not examined here because it is not of interest for our current research question.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.