Cognitive-motor interference has been extensively studied, yet our understanding of
their interaction remains complex and varied. The present study examines the
relationship between cognitive conflict induced by the Flanker Task and postural
control measured by a force plate. In Experiment 1 (N = 69) we presented an equal
number of congruent and incongruent Flanker stimuli (letter version of the Flanker
Task) to participants while they were standing on a force plate. Secondly,
(Experiment 2, (N = 65), the proportion of incongruent to congruent Flanker stimuli
was manipulated across blocks, including both 75/25 and 25/75 ratios (proportion
congruency manipulation). We examined reaction times in the cognitive task and
analyzed postural sway variability data from the force plate with an event-related
approach (i.e., continuous force-plate data were analyzed through cluster-based
permutation tests). The expected congruency effect on reaction times was confirmed,
along with a modulation of this effect based on the proportion congruency
manipulation (i.e., larger congruency effects in the condition with 25% incongruent
and 75% congruent trials). Cluster-based permutation analysis of postural control
revealed a congruency-specific effect on sway variability after stimulus presentation
in the first Experiment. Sway variability was reduced in congruent compared to
incongruent trials when they followed congruent trials. There was also a general
increase in sway variability following both, congruent and incongruent stimuli
presentations (i.e., after target onset). These findings highlight the interplay between
cognitive conflict and postural control, suggesting that postural adjustments are
sensitive to cognitive demands.