Scientific Results
According to Timothy Salthouse, key findings from the VCAP regarding longitudinal cognitive change include:
| Age-Related Shift in Cognitive Change | There is a transition from positive cognitive change at younger ages to negative change as individuals grow older. |
| Retest Effects Influence Positive Change | A significant portion of the observed positive change can be attributed to retest effects. This has been demonstrated through methods like the twice-minus-once-tested and quasi-longitudinal procedures. |
| Domain-General Nature of Change | Much of the cognitive change is not confined to specific abilities but is rather domain-general. This is evident through statistical controls for general cognition estimates, positive correlations among different change measures, and reduced covariance in repeated measures over time, particularly when analyzed within a hierarchical framework. |
| Impact of Time and Occasions on Change | Longer intervals between assessment occasions tend to be associated with more negative cognitive changes. Conversely, having additional occasions generally correlates with more positive changes. |
| Performance and Decline in Older Participants | Older participants who return for subsequent assessments tend to exhibit higher cognitive performance levels initially. However, their rate of cognitive decline does not appear to be steeper compared to those who drop out of the study. |