Contrasting cognitive control in the Simon and spatial Stroop tasks regarding their interference with the control of standing balance

The scientific understanding of any interaction between cognition and balance control is advanced by methods that capture event-related effects of cognitive processes on balance with high temporal resolution and precision. We developed such an approach to examine how cognitive conflict interferes with the control of body balance during upright standing. Participants stood on a force plate while performing two cognitive conflict paradigms: a Simon task, which induces spatial stimulus–response conflict during response selection, and a Spatial Stroop task, which elicits an additional stimulus–stimulus conflict during stimulus encoding. By aligning force plate time series data to the onset events of target and response across all trials, we assessed the temporal dynamics of spatial congruency effects on force moment variability as a marker of balance control activity. Across both experimental cognitive tasks, incongruent trials produced strong congruency effects in cognitive task performance and systematically caused transient reductions in force moment variability along the mediolateral axis in balance control. These observations suggest that the recruitment of cognitive processes for conflict resolution temporarily inhibits, suppresses, or postpones balance adjustments. Importantly, regarding the impact of cognitive interference on body balance, we confirm our previous observations using improved methods and demonstrate that reduction in balance control activity during resolution of cognitive conflict generalizes to a task with multiple conflict loci (Spatial Stroop task). However, this extended range of conflict does not result in correspondingly stronger interference effects in balance control. These findings suggest that conflict-related demands in cognitive control robustly permeate into balance control. From a theoretical perspective, the results align with predictive models of postural regulation and intermittent, event-driven accounts of balance control.