Dehaene’s team adjusted the test, making the interval between tasks longer or shorter. After each task, the volunteers had to estimate how long it took to carry it out; then the scientists showed them their actual time. After a few sessions, the volunteers got fairly good at guessing how much time had passed.
The researchers found that the psychological refractory period stopped this mental clock. If a task was stuck in a bottleneck, people did not start timing it. The brain began measuring how long a task took only after the previous task moved out of the bottleneck. Whenever a perception of a sound or a letter got stuck in the mental traffic jam, the subjects were not aware of it.
The article seems to explain why I (and everyone else) always found it so hard to accurately measure the time I spent on a given problem. Basically my brain would jam up with the problem in front of me and my internal clock would go on hold until I finished the problem. But by using the
I was able to train myself to predict when I was getting close to the 2 minute mark.