A memory-theoretic account of citation propagation

Abstract

Despite the common assumption that citations are indicative of an article's scientific merit, increasing evidence indicates that citation counts are largely driven by variables unrelated to quality. In this article, we treat people's decisions of what to cite as an instance of memory retrieval and show that observed citation patterns are well accounted for by a model of memory. The proposed exposure model anticipates that small alterations in factors that affect people's ability to retrieve to-be-cited articles from memory early in their life cycle are magnified over time and can lead to the emergence of highly cited papers. This effect occurs even when there is no variation in the starting point exposure probabilities (i.e. when assuming a level playing field where all articles are treated equally and of equal 'quality'), and is exacerbated by natural variation in retrievability of articles due to encoding. We discuss the implications of the model within the context of research evaluation and hiring, tenure and promotion decisions.

Keywords: bibliometrics; citation counts; information search; memory; research evaluation.

Figure 1.

Density plots of the memory-theoretic model’s predicted distribution of citation counts as a function of the encoding parameter. The tick marks at the bottom correspond to individual articles.

Figure 2.

Density plots of the memory-theoretic model’s predicted distribution of citation counts as a function of the similarity of articles. The tick marks at the bottom correspond to individual articles.

Figure 3.

(a–f) Density plots of actual citations (red) and model predictions (blue) for 3 years of publications. Model predictions are based on the median value of each quantile across 100 simulations for each year.

Figure 4.

Plots of best fitting encoding parameter as a function of publication year (a) and predicted number of papers with zero citations for both the stochastic model (b) and the memory-theoretic model (c).

Figure 5.

Plot of the predicted evolution of citation probabilities over time for the memory-theoretic model for year 1989. Main panel shows first 5000 epochs. The inset shows evolution over all epochs. Each line represents a different quantile (1.0, 0.99, 0.95, 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, 0.20, 0.10, 0.05, 0.01 and 0.00) based on the final probabilities. The thick back-dashed line corresponds to the 50th percentile of the distribution. Quantiles ending above 0.5 are represented by solid lines, whereas those ending below 0.5 are dotted. The red-dashed line corresponds to the starting point probabilities.