Response Variability in Attention-Deficit Disorders

Reaction times in a mental rotation task were measured across a diverse population that sorted into two groupings based on overall variability. Although both the low- and the high-variance groups produced data that displayed the trends typical of mental rotation, the two groups' reaction time sequences had very different auto-correlation functions. Power spectra derived from the two groups' data showed the presence of distinctive noise processes with long memory. Normal levels of variance were associated with 1/f noise, whereas high-variance data had substantial traces of random walk contour. These findings provide new perspectives on cognitive assessments of attention dysfunction.