Use of a robot arm in study of the motion perception process cd.

4. Experiment

When we are walking through the room we usually observe all the objects like furniture to avoid the collision with them, although we are usually not aware of that. Thank to the construction of our eyes we are able to see in 3D and judge the distance to for example the table standing in the middle. But what happens when someone turns the light off? If we had enough time to make in our brain the map of surrounding we would not have difficulties to walk in the room without hitting anything. It means however that during measuring the distance eyesight is not the only sense that we use.

To examine human orientation in the space and the ability to estimate the distance in the dark the following experiment was run. The object was sitting on the end effector of the KUKA arm in car racing chair. The room was absolutely dark. The special chair gives the feeling of safety and prevents the object from unwanted movements in the experiment. Suddenly, somewhere in the room flashes light. The task of the investigated person was to move the end effector, using the steering wheel, exactly to the place where the light flashed and push the button. The trajectory of the end effector was always a circle sector and the radius was constant.

During the experiment we tested what does influence human ability to estimate the distance, when brain receives no visual signals. The factors like speed, distance from the flashing light and tilt of the chair were proved. Tilt of the person should cheat the brain and give the feeling of additional acceleration and in this way disturb the process of estimation, because we assumed that people would be measuring how long do they move with given speed to judge the distance they have travelled. Each examined person repeated the experiment 150 times, every time with different settings. The results were really surprising. First of all it appeared that driving experience or playing PC games is not a very important factor – we assumed that such people will have fewer difficulties with “feeling” the steering wheel. We expected also that there

will be difference between men and women, which was not observed. We proved however another statement, that the smaller distance, the better was the estimation. By the most of the objects there was a very strong relationship between those two values. What we found especially interesting is that some people have the tendency to overvalue and some to underestimate the distance. It almost didn’t happen that the same person passed the correct position in one measurement and in the next one underestimated the range. Additionally people tend to stop earlier than drive too far, what can be easily explained: it’s always safer to keep the distance than to hit something. By some people the difference between driving left and right was observed. We can not however clearly say that it is connected with the fact if the person was left- or right-handed, because the steering wheel was not symmetric – the object had to press the button with the right hand (and thus keep one finger on it all the time) what could influence the steering process.

The author: Agnieszka LEYKO

REFERENCES [1]

http://www.kyb.tuebingen.mpg.de/bu, 25th March 2008