Intraindividual variability, how do I measure thee? Let me count the ways

Area of Science:

• Cognitive psychology
• Psychometrics
• Educational psychology

Background:

• Intraindividual variability (IIV) is crucial for understanding cognitive processes.
• Existing research often uses diverse conceptualizations and operationalizations of IIV.
• The relationship between different IIV metrics and their predictive validity for outcomes like academic achievement requires further investigation.

Purpose of the Study:

• To examine the interrelations among different types and metrics of intraindividual variability (IIV).
• To assess the predictive utility of various IIV operationalizations for academic achievement.
• To clarify the conceptual and methodological considerations for measuring IIV.

Main Methods:

• Calculated three types of IIV (inconsistency, dispersion, dispersion of inconsistency) using multiple metrics (standard deviation, coefficient of variability, residualized standard deviation).
• Assessed IIV within and across six cognitive and math-related measures in 238 young adults.
• Separated score from response time for each measure to analyze their unique contributions.

Main Results:

• Metrics of variability were interrelated, but inconsistently.
• The significance of inconsistency IIV metrics for predicting academic achievement depended heavily on the specific measure and inclusion of the primary score.
• Dispersion and dispersion of inconsistency metrics were often significant predictors, but this effect diminished when the primary score was included in models.

Conclusions:

• Concurrent examination of multiple IIV types and metrics reveals complexities in their measurement and prediction.
• Clarifying the specific type of IIV, the rationale for chosen measures (especially dispersion), and including score alongside timing is essential.
• Standardizing IIV measurement will enhance generalizability and guide future psychometric and clinical research.