Temporal structures in sensorimotor variability are reliable… but what for?

Human performance is characterised by endogenous variability, which often shows dependency over time. However, studies on these temporal structures typically stay limited to showing that the structures exist in a particular data series. As such, their underlying mechanisms and informativeness for cognitive psychology are largely unknown. Two recent studies reported between-subject correlations between temporal structures and task performance on the same data series, but with contrasting results. In the current work, we investigated the intra-individual repeatability and inter-individual correlates of temporal structures in sensorimotor variability across the most commonly used measures – aiming to examine to what extent these structures are informative for studying individual differences. To capture endogenous sensorimotor variability, participants completed the Metronome Task – in which they press in synchrony with a tone. Occasionally, participants were presented with a thought probe, and were asked to rate their current subjective attentional state. Results indicate that autocorrelation at lag 1 and Power Spectra Density (PDS) slopes show good repeatability, while Detrended Fluctuation Analysis (DFA) slopes only show moderate repeatability, and ARFIMA(1,d,1) repeats poorly. Autocorrelation and PSD, and DFA to a lesser extent, correlated with task performance on the same data series – such that well-performing participants showed less dependency. However, temporal structures did not correlate with mean attentional state ratings nor with self-assessed ADHD tendencies, mind wandering, and impulsivity – negating assumptions that these structures arise due to fluctuations in internal meta-cognitive states. Overall, while temporal structure may be a reliable trait, its usefulness for studying individual differences is yet to be identified.