Genetic analysis of reaction time variability: room for improvement?

Area of Science:

• Cognitive Neuroscience
• Psychiatric Genetics

Background:

• Increased reaction time variability (RTV) is a hallmark of several psychiatric disorders, notably attention deficit hyperactivity disorder (ADHD).
• While RTV can improve with rewards in ADHD, the interpretation of baseline RTV versus RTV difference scores remains debated.
• State regulation theory posits that RTV difference scores capture 'state regulation', but the etiological basis of baseline RTV is less clear.

Purpose of the Study:

• To investigate the phenotypic and etiological overlap between reaction time variability (RTV) baseline and RTV difference scores.
• To clarify the underlying genetic and familial factors influencing RTV measures in attention deficit hyperactivity disorder (ADHD).

Main Methods:

• Genetic model fitting analyses were performed on go/no-go and fast task RTV data.
• Data were analyzed across different task conditions manipulating rewards and event rates.
• The study utilized a population-based twin sample (n=1314) and an ADHD/control sibling-pair sample (n=1265).

Main Results:

• Phenotypic and genetic/familial correlations between RTV baseline and difference scores were consistently high (0.72-0.98) across tasks and samples.
• In contrast, correlations were low between RTV in manipulated conditions and RTV difference scores.
• Two different RTV difference scores from go/no-go tasks showed high phenotypic and genetic/familial overlap (r=0.75-0.83).

Conclusions:

• RTV difference scores largely measure the same etiological processes as RTV under baseline conditions.
• Findings support theories on the malleability of high RTV in ADHD.
• Baseline RTV scores are recommended for most analyses, including genetic studies, due to statistical advantages over difference scores.