Information processing limit is a fundamental issue in cognitive psychology. One particular way of studying it is to adopt a temporal span perspective. In this experiment, Weber fractions based on thresholds for duration discrimination are used for adopting this perspective. The results showed that, contrary to the constant predicted by Weber's law, the Weber fraction is larger at 2 than at 0.2s. This increase is observed in conditions where inter-trial intervals and cognitive load are manipulated, and is argued to be due to the fact that 2s is beyond a temporal span limit for processing information.