People have an aftereffect after jogging on a treadmill with eyes closed or blindfolded, in that they tend to move forward when trying to jog in place. For this study five participants were blindfolded and five had clear vision. Participants jogged in place before and after jogging on the treadmill; the mean differences in distances before and after were compared. The clear vision group moved further after than before the treadmill than the blindfolded group, but the results were not statistically significant. The expectation was that the blindfolded group would have a larger aftereffect than the clear vision group. The study had many limitations, especially that subjects, psychology students, were not naïve, and the study was small.
Introduction
After jogging on a treadmill, people get an aftereffect, a feeling they are still on the treadmill. In many experiments, when people are blindfolded after jogging on the treadmill jogging in place they tend to not notice that they are actually moving forward but when people have clear vision after jogging on the treadmill, they tend to not have much of the aftereffect. This study attempted to use a treadmill to assess the effect of visual cues on this aftereffect.
Treadmills have been used as a way of studying how sensory and motor activities result in aftereffects, whether in speed of locomotion, direction, or distance (Earhart, Anstis). In 1995, Anstis, et al. reported that there are jogging aftereffects especially within a short time after running on a treadmill. In his experiments, after running on the treadmill people had more of a tendency to jog forward when trying to run in place with their eyes closed. This aftereffect gradually declined after delays of 15 to 120 seconds. Shortly after, Peleh, et al., published data showing an additional aftereffect of using a treadmill, which was a sensation of accelerated self-motion when walking immediately after using the treadmill compared to beforehand. Exploring Anstis’s finding further, Durgin, et al. in 1999 sought evidence for after effects in the “real world,” first, people running behind a golf cart, and second, with people running on the treadmill with a simulated visual flow fields at different speeds. They did their golf cart experiment with eyes closed and eyes open and with and without auditory stimuli. They found that visual information reduced the amount of after effect but that speed level of “visual flow” on the second experiment was not associated with amount of aftereffect. Also, auditory information reduced the after effect under all conditions. Mohler, et al. conducted experiments with treadmills and virtual environments created by CGI graphics that demonstrated that the recalibration of motion after a treadmill is related more to the visual perception of speed of self-movement, not the optical perception of movement.
Method
Participants
The participants were 10 undergraduates from George Washington University. There were 3 males and 7 females of ages ranging 20-23.
Apparatus
Participants ran on a treadmill machine that is located in the GW psychology laboratory in Building GG. The treadmill had a variable speed controlled with a lever, and a small screen that was covered with a piece of paper. Next to the treadmill was a taped “X” to mark the spot where participants were to start jogging in place. The experiment also required a blindfold and a tape measure.
Design
The independent variable was the different conditions –whether or not the participant was blindfolded. The dependent variable was the additional distance they moved forward when they jogged in place after jogging on the treadmill compared to before jogging on the treadmill.
Procedure
Each person was assigned to either the blindfolded, or the clear vision group. Those in the blindfolded group were blindfolded throughout the whole experiment; those in the clear vision group were not blindfolded at all. First, participants were told to stand on the tape at the “X” mark, and jog in place for 20 seconds. The distance that was travelled was measured, in the forward direction, from the “X” (distance1). Then they moved to the treadmill and lightly jogged (at medium speed) for 60 seconds. After that, they once again jogged in place on the taped “X” and the second distance forward was measured (distance2). The difference between the two distances was calculated as distance2 minus distance 1.
Results
Both groups had a treadmill aftereffect when jogging in the place. The blindfolded group moved between 2 and 32 inches forward of the “X” with a median of 12.0 and a mean of 12.6 inches, SD 11.46, SEM 5.12. The clear-sighted group moved between 6 and 26 inches forward with a median of 14.0 and a mean of 13.6, SD 8.02, SEM 3.59 (See Table 1 and Figure 1). On average the clear-sighted group moved further, however, the P-value= 0.8769 for a two-tailed T-Test, which is not statistically significant.
Discussion
The data did not support the hypothesis because both the blindfolded, and the clear vision group experienced a similar amount of treadmill aftereffect. While the clear vision group on average had a slightly stronger aftereffect, the difference was not statistically significant. As expected according to Anstis, the aftereffects occurred even after a very short period of time on the treadmill.
There could be many explanations for the insignificant results. There was a limited sample size. In such small samples individuals can be influential. For example, one of the participants in our blindfolded group had an unusually high difference, 32 inches or 50% more than the next highest person and another one had an unusually low difference, only 2 inches. Likewise, there was a lot of variability among the participants in the clear sight group. The sample of people in this study were not “naïve” like in the Anstis study but instead were psychology students who already had heard about this experiment in class, so the participants could have been aware that aftereffects were expected, perhaps causing exaggerated effects in both groups. As another factor, the room was very hot that day, possibly affecting (or slowing down) jogging behavior. The corner of the room that was used for the experiment was very small, so that is possible that participants were cautious about bumping into something. The small room also could have affected people’s visual perceptions. Also, it could be observed that participants were jogging in place differently, some making considerable efforts and others barely moving their feet. Thus, there were many possible biases. For further research, there should be a larger sample size and an even number of females and males. Perhaps the design could test each subject in each condition, in random order, to help account for individual variability in factors like how they jog.
It also would have been interesting to explore the effects of auditory cues. For example, in a future experiment we could have the participants carry out the study with and without ear plugs to test the effect of hearing cues.