Psychol Assess. 2016 Feb;28(2):171-80. doi: 10.1037/pas0000177. Epub 2015 Jun 8.
Rule switching is 1 among a diverse set of executive functions whose delicate interactions allows us to coordinate behavior appropriately to changing contexts and demands. Clinical assessments such as the Trail Making Test (TMT) estimate flexibility of rule switching, but such assessments can be challenging to interpret. TMT scores are sums of many choice response times (RTs): More time spent reflects not simply manual motor speed and visual scanning but also fluctuation of attention to sequence and less flexible switching among rules to reject many inappropriate targets and instead select the single next appropriate target. A growing consensus recognizes that the aggregate of many choice RTs reflect multiplicative interaction of factors across multiple scales, among which manual motor speed, counting up sequence, and rule-switching are just a few. Multiplicative interactions entail first, fractal temporal correlations and, more importantly, variability of fractality within the same series, that is, “multifractality,” The authors analyzed circle-tracing data to test whether tracing variance, degree of fractal temporal correlations, and multifractality correlate with TMT scores. Despite the absence of effects of variance, stronger temporal correlations indicated poorer Trails B performance, but multifractality moderated this relationship. These results suggest potential markers for predicting rule-switching ability from motor behavior. (PsycINFO Database Record