Open Access
Karalunas, Sarah Lyn
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
December 07, 2010
Committee Members:
  • Cynthia Huang Pollock, Ph D, Dissertation Advisor
  • Cynthia L Huang Pollock, Committee Chair
  • Lisa Michelle Kopp, Committee Member
  • Rick Owen Gilmore, Committee Member
  • Judith Fran Kroll, Committee Member
  • motivation
  • variability
  • ADHD
  • attention
STUDY 1 examined patterns of reaction time (RT) variability in children with and without ADHD under different motivational contexts. Seventeen children with ADHD and 20 typically-developing controls completed a go-no/go task that included baseline and motivational conditions. Children with ADHD were less accurate than non-ADHD controls in both conditions and responded more slowly than non-ADHD controls when motivational incentives were introduced. Fast-Fourier transform (FFT) analyses indicated that children with ADHD were more variable than non-ADHD controls at both high and low frequencies, but that group differences were greatest at low frequencies. Motivational incentives did not impact patterns of variability. Results are consistent with previous studies suggesting that low-frequency patterns of RT variability characterize task performance of children with ADHD. Lack of impact of motivational incentives implicates trait, rather than state, factors in determining patterns of variability. STUDY 2 examined physiological correlates of RT variability in typically-developing children. Twenty-six typically-developing children completed a go-no/go task while physiological measures of attention were collected. Variability of RTs, as measured by standard deviation of RT (SDRT), was marginally negatively correlated with baseline respiratory sinus arrhythmia (RSA). Although the correlation between electroencephalogram (EEG) beta activity on go trials and SDRT was not significant, the effect size for the correlation was large. Results provide physiological corroboration of theories suggesting that RT variability in children reflects attentional lapses, specifically difficulties with orienting.