Tyler M. Miller

Dementia Staging across Three Different Methods

Background/Aims: To investigate the effectiveness of an item response theory (IRT)-based approach to staging dementia. Methods: IRT estimates of dementia severity in 1,485 patients were used to stage dementia and then compared to dementia staging using the classic Clinical Dementia Rating Scale (CDR) algorithm and the Sum of the Boxes (SOB) approach. Results: Measurement imprecision was highest when dementia stages were determined based on the classic algorithm (48% of sample), lower when they were determined based on the SOB approach (12%), and lowest when determined using IRT-based staging (0%). Conclusion: The classic CDR algorithm weights boxes largely according to clinical experience. The SOB approach weights all boxes equally. The IRT approach weights boxes according to their actual ability to identify dementia severity and therefore provides the most precise information for staging dementia.

The bizarreness effect: evidence for the critical influence of retrieval processes

People show better memory for bizarre sentences relative to common sentences, a finding referred to as the bizarrness effect. Interestingly, this effect is typically only obtained using a mixed-list design, in which participants study common and bizarre sentences in the same list. This bizarreness effect in mixed-list designs has been explained as the result of both enhanced encoding processes and efficient retrieval processes. The present experiment was designed to isolate the unique contributions of the retrieval context to the bizarreness effect. Participants studied common sentences in one room under one set of instructions, and bizarre sentences in another room under another set of instructions. At test, participants recalled the common and bizarre sentences either together or separately. The results showed that the bizarreness effect was only obtained when participants recalled the common and bizarre items together; no bizarreness advantage emerged when participants were required to recall the common and bizarre items separately. These results suggest that differential encoding processes are not necessary for explaining the bizarreness effect in memory. Rather, retrieval of the mixed-list context appears to be critical for obtaining the effect.

Item Response Theory Reveals Variability of Functional Impairment within Clinical Dementia Rating Scale Stages

Background/Aims:To investigate whether an item response theory (IRT) approach to measuring variations of dementia severity within Clinical Dementia Rating (CDR) stages is associated with activities of daily living (ADLs). Methods: IRT estimates of dementia severity within CDR stages in 1,181 patients were correlated with ADLs and analyzed. Results: IRT-determined dementia severity was significantly correlated with ADLs in three of four impaired dementia stages. Conclusion: An IRT approach shows considerable advantages over traditional scoring practices of the CDR not only because it increases precision in dementia measurement, but also because it enables one to discover more precise associations with functional outcomes such as ADLs.

The Effect of Prior Task Success on Older Adults’ Memory Performance: Examining the Influence of Different Types of Task Success

Background/Study Context: Negative aging stereotypes can lead older adults to perform poorly on memory tests. Yet, memory performance can be improved if older adults have a single successful experience on a cognitive test prior to participating in a memory experiment (Geraci & Miller, 2013, Psychology and Aging, 28, 340–345). The current study examined the effects of different types of prior task experience on subsequent memory performance. Methods: Before participating in a verbal free recall experiment, older adults in Experiment 1 successfully completed either a verbal or a visual cognitive task or no task. In Experiment 2, they successfully completed either a motor task or no task before participating in the free recall experiment. Results: Results from Experiment 1 showed that relative to control (no prior task), participants who had prior success, either on a verbal or a visual task, had better subsequent recall performance. Experiment 2 showed that prior success on a motor task, however, did not lead to a later memory advantage relative to control. Conclusion: These findings demonstrate that older adults’ memory can be improved by a successful prior task experience so long as that experience is in a cognitive domain.

Greater precision when measuring dementia severity: establishing item parameters for the Clinical Dementia Rating Scale.

Background/Aims: An item response theory (IRT)-based scoring approach to the Clinical Dementia Rating Scale (CDR) can account for the pattern of scores across the CDR items (domains) and their differential abilities to indicate dementia severity. In doing so, an IRT-based approach can provide greater precision than other CDR scoring algorithms. However, neither a good set of item parameters nor an easily digestible set of instructions needed to implement this approach is readily available. Methods: Participants were 1,326 patients at the Baylor College of Medicine Alzheimer’s Disease and Memory Disorders Clinic. Results: The item parameters necessary for an IRT-based scoring approach were identified (a parameters ranged from 3.01 to 6.22; b parameters ranged from –2.46 to 2.07). Conclusion: This study provides, and demonstrates how to easily apply, IRT-based item parameters for the CDR.