Change in intraindividual variability over time as a key metric for defining performance-based cognitive fatigability

Area of Science:

• Cognitive Neuroscience
• Psychology
• Human Performance

Background:

• Cognitive fatigability is typically measured by average reaction time (RT) or error rates.
• These traditional metrics may not fully capture the nuances of cognitive fatigue.
• Intraindividual variability in performance is proposed as a more sensitive indicator.

Purpose of the Study:

• To investigate if changes in intraindividual variability are a more sensitive metric for cognitive fatigability than mean performance.
• To explore the relationship between intraindividual variability changes and subjective fatigue perceptions.
• To understand the cognitive control mechanisms underlying fatigue-related performance changes.

Main Methods:

• Fifteen young adults performed a three-hour cued Stroop task.
• Subjective fatigue was assessed using the Multidimensional Fatigue Index (MFI).
• Behavioral data (RT, accuracy) and RT variability (coefficient of variation) were analyzed over time.

Main Results:

• Intraindividual RT variability increased linearly over three hours, showing a larger effect size than mean RT or accuracy.
• Increased RT variability correlated significantly with subjective reports of reduced activity, motivation, and mental fatigue.
• RT distribution analysis indicated increased variability reflects attentional lapses or cognitive control breakdowns.

Conclusions:

• Changes in intraindividual variability over time are a sensitive and ecologically meaningful metric for cognitive fatigability.
• This metric offers insights into the neuronal mechanisms of fatigue perception and performance decline.
• Intraindividual variability analysis may enhance the assessment of cognitive fatigue in various contexts.