IntroductionSeveral studies have shown that the working memory is sensitive to temporal variations. We used a new visuospatial working memory task, the “Time Squares Sequences,” to investigate whether implicit variations in stimuli presentation time affect task performance.MethodsA total of 50 healthy participants saw two sequences (S1 and S2) of seven white squares presented in a matrix of gray squares and assessed whether S2 matched S1. There were four conditions depending on the spatial position and the presentation time (i.e., timing) of the white squares in S1 and S2: two with the same (S1 fixed/S2 fixed and S1 variable/S2 variable) and two with different (S1 fixed/S2 variable and S1 variable/S2 fixed) presentation times.ResultsFindings showed impaired performance when S1 had a fixed presentation time and S2 had a variable presentation time.ConclusionThese findings are attributed to increased cognitive load due to S2 timing difference, pointing to a monitoring process, sensitive to temporal variations.