Time-on-task in children with ADHD: an ex-Gaussian analysis

Area of Science:

• Neuroscience
• Cognitive Psychology
• Child Psychiatry

Background:

• High intra-individual variability (IIV) is a recognized characteristic of attention deficit/hyperactivity disorder (ADHD).
• Previous research has not detailed the IIV pattern over the course of a cognitive task in ADHD.
• Understanding response time fluctuations is crucial for characterizing ADHD's impact on sustained attention.

Purpose of the Study:

• To investigate the pattern of IIV during a cognitive task in children with ADHD compared to controls.
• To explore the utility of the ex-Gaussian approach in analyzing response time variability in ADHD.
• To determine if sustained attention deficits in ADHD can be identified through IIV analysis early in a task.

Main Methods:

• Administered the Conners' Continuous Performance Task (CPT-II) to 30 children with ADHD and 30 controls.
• Utilized an ex-Gaussian approach to analyze across-block individual response time (RT) performance.
• Compared conventional measures of central tendency with ex-Gaussian parameters (mu and tau).

Main Results:

• Conventional measures showed group differences in mean RTs but similar trends across blocks.
• Ex-Gaussian analysis revealed no significant differences in the normally distributed RT component (mu) between groups.
• Children with ADHD exhibited a marked increase in the exponentially distributed RT component (tau) across blocks, indicating progressively longer RTs.

Conclusions:

• The ex-Gaussian approach provides a more nuanced understanding of RT variability in ADHD than traditional methods.
• Sustained attention deficits in ADHD are characterized by increasing IIV, particularly in the tail of the RT distribution.
• Analyzing IIV within the initial blocks of a cognitive task can effectively detect sustained attention deficits in ADHD.