Cognitive control refers to the processes that permit selection and prioritization of information processing in different cognitive domains to reach the conscious mind.Although previous studies have suggested that the capacity of cognitive control is limited,a direct quantification of this capacity has not been attempted.In this behavioral study,we manipulated the information rate of cognitive control by parametrically varying both the uncertainty of stimuli measured as information entropy and the exposure time of the stimuli.We used the relationship between the participants response accuracy and the information rate in bits per second(bps)in the model fitting to estimate the capacity of cognitive control.We found that the capacity of this higher-level function of cognitive control was approximately 3 to 4 bps which is remarkably low.Theoretical significance and clinical implications of the quantification of the capacity of cognitive control will be discussed.