Modeling storage and retrieval processes with clinical populations with applications examining alcohol-induced amnesia and Korsakoff amnesia

Multinomial processing tree models can provide for measures of underlying cognitive processes. In this paper, the Chechile [Chechile, R. A. (2004). New multinomial models for the Chechile-Meyer task. Journal of Mathematical Psychology, 48, 364-384] 6P model is described and applied to several applications involving clinical populations. The model provides for separate measures of storage and retrieval. Monte Carlo studies were conducted to examine the relative accuracy of two methods for obtaining an overall condition estimate for the 6P model, i.e., averaging estimates found for individuals versus pooling the multinomial frequency data before estimating the model parameters. The sampling studies showed that the pooling of frequencies resulted in more accurate parameter estimates. However, psychological assessment in clinical psychology requires precise measurement on an individual basis. In order to recover information about individuals from pooled frequency information, a modified jackknife method was advanced. The jackknife method is based on a contrast between the overall pooled frequency information and the pool frequency without the observations from a single individual. Another series of Monte Carlo simulations demonstrate that the new jackknife method resulted in better recovery of the correct individual parameter values relative to estimates based on only the data from the individual. Finally, the 6P model was used to examine the data from two previously reported studies with clinical populations. One application addressed the effect of alcohol-induced amnesia, and the other application dealt with Korsakoff amnesia. In both cases the pattern of storage and retrieval measurements resulted in a clarification of the underlying storage and retrieval differences between the clinical group and the control group.