Posterior distribution analysis of the retention of briefly studied words

The way in which memories decline over time has been studied for over a century, but remains an unresolved issue because of a lack of sufficiently precise data and effective model selection techniques. Here we address this gap with a particular focus on whether the decline in memory retention is complete or asymptotes above chance performance. We collected stem cued recall and stem completion data with tighter control over levels of interference and more data per retention interval than most previous studies. We analyzed the data using Hierarchal Bayesian models free from assumptions regarding the functional form of the forgetting curve. Population distribution estimate of retention at one hour well above the chance completion rate provided strong evidence for the use asymptote parameters in models of retention regardless of the functional form of the model.