In a senior research class, several students decided to see if the perception of the passage of time was influenced by age. They asked volunteers to participate in a time estimation task. Participants were first asked their age. Then, they were told that as soon as a green light flashed on the computer monitor in front of them, they were to begin estimating a 27-second time interval, without counting or using any kind of timing device. As soon as the participant felt that the indicated interval had passed, she or he pressed the space bar on the keyboard. The actual duration of the time interval that had passed was then presented on the monitor, followed by a warning tone and the next trial. The table below shows the mean errors (in milliseconds) made by the participants for each time interval. Positive errors indicate an overestimation of the time interval, and negative errors indicate an underestimation of the time interval. Participants in age group 1 were between 10 and 21 years of age. Participants in age group 2 were over the age of 50.