Task Complexity Amplifies Practice Effects on Quarterly Self-Administered Cognitive Tasks (Preprint)

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Abstract
BACKGROUND Remote, self-administered digital assessments provide scalable approaches for monitoring cognition in older adults. Practice effects (PE), once viewed as measurement noise, are increasingly recognized as potential markers of cognitive decline. As disease-modifying therapies for neurodegenerative conditions emerge, longitudinal digital assessments may capture subtle cognitive changes. Although the majority of PE studies have focused on memory tasks, it is critical to determine whether PE occur in other domains. Clarifying the potential presence of PE across multiple timepoints on the FDA-cleared Defense Automated Neurocognitive Assessment (DANA) platform remains critical for determining whether PE can serve as a measure of cognitive decline longitudinally. OBJECTIVE To examine whether PE occur across quarterly self-administrations of digital cognitive tasks across different cognitive domains. Demographic characteristics were examined as potential moderators. METHODS Cognitively intact older adults from the Framingham Heart Study self-administered DANA tasks at baseline and every three months for one year (four assessments, T1-T4). Tasks included Simple Reaction Time (SRT), Go/No-Go (GNG), and Code Substitution (CS). These tasks varied in complexity, from simple motor responding (SRT) to inhibitory control (GNG) and associative learning with working memory demands (CS). The primary outcome was Cognitive Efficiency, a derived measure of speed and accuracy, which are also recorded as secondary measures. PE were quantified using linear mixed-effects models and change in mean score across timepoints expressed in pooled SD units expressed as Cohen d. RESULTS A total of 717 participants completed all four timepoints (mean age: 64.1±9.5 years; 65.4% females; 67.1% college educated). PE were observed on all tasks with small effect (d: SRT=0.16, GNG=0.32, CS=0.43). Demographics influenced baseline performance: older age predicted lower baseline scores on all tasks, females scored lower on SRT and GNG, and higher education predicted better performance on all tasks. Age was the only demographic moderator of PE, with smaller improvements on CS among participants >65 years (β=-0.39, P<.001). CONCLUSIONS Quarterly self-administered digital cognitive assessments elicited measurable PE across processing speed, inhibitory control, and visual scanning, with stronger effects on more complex tasks. Demographics influenced baseline performance, while age moderated PE on the most demanding task. These findings underscore the importance of characterizing PE in digital assessments and highlight their potential clinical utility in detecting early cognitive impairment.

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