All the time perception tasks require the ability to allocate attention; however, different tasks involve other different mental abilities for estimation of duration of presentation of a target. Verbal estimation task is more related to the length of one's subject time unit, as synonymous inner clock speed. Time discrimination and time reproduction are related to the duration comparison. In addition to estimating the duration in the time discrimination task, subjects need to allocate their attention for a longer time and then to produce a target with the same duration by using some executive functions such as behavioral inhibition, sustain attention and working memory.