# Statistical Anaylsis of Human Grasping

Essay add: 30-09-2015, 10:12   /   Views: 163
Statistical Anaylsis of Human Grasping

As the size of the object increases, so does the number of fingers used to grasp the object. The preferred grasp for the marble was the same as the minimum, and close to the number of maximum fingers used. Two fingers was the mean for the preferred and minimum and the maximum was 2.5 with a standard deviation of .2. The mean of the preferred grasp of the golf ball was 2.7 fingers, with a standard deviation of .2. It was above the minimum number of fingers used, which was 2, and below the mean of the maximum grasp, which was 3.8 with a standard deviation of .3. The mean of the preferred grasp of the tennis ball was 3.5 with standard deviation of .3. Two was the minimum grasp of the tennis ball, while the maximum grasp was 4.2 with a standard deviation of .3. The preferred grasp of the softball was 4.5 with a standard deviation of .2, which is double the mean of the minimum grasp, which was 2.2 with a standard deviation of .2. However, the mean of the preferred grasp is close to the maximum grasp, which was 5. The grasp of the basketball is unique in comparison to the other objects. It had no deviation in the grasps for any of the subjects tested. The mean of the preferred and the maximum grasps were the same, being 10 fingers, and the minimum grasp was 6 fingers.

The preferred grasp for the smallest sphere, the marble, was the same as the minimum, both being 2 fingers. For the largest sphere, the basketball, the preferred grasp was the same as the maximum grasp, both being 10 fingers. For the other three balls, the preferred grip was in between the minimum and maximum grips. The preferred grasp for the golf ball was closer to the minimum grasp than the maximum grasp. The preferred grasp for the tennis ball was closer to the maximum grasp than to the minimum grasp, and the preferred grasp for the softball was also closer to the maximum grasp than to the minimum grasp. For the previous 3 objects, the subjects did not use the maximum or minimum number of fingers used because it was more natural for them to pick up the ball in another way, therefore spreading their fingers out more to grasp the object effectively and naturally. Another reason would be because there are many degrees of freedom and different restraints.

Sometimes the task of grasping an object differs because of constraints. One constraint could be the task that is asked to be performed by the subject. For example, if the subject is asked to grasp an object while wearing a glove, or if they are asked to move an object as fast as possible, these tasks may have an effect on the way they must hold the object. Another constraint may be environmental. The conditions that are surrounding the subject may have an effect on their grasp. Two examples of this are rain and wind. If it is raining, the object may be slippery, therefore making the subject grasp it differently. Also, if it is extremely windy, the subject might have to hold an object with a different grasp to prevent it from going out of his/her hand. The last kind of constraint that could effect the subject’s grasp of an object is the features of the organism itself. Two examples of this type of constraint would be stiffness and strength. If the subject is lacking strength or full mobility (due to stiffness) in their hands, the way they grasp the ball will be affected. They will need to use more fingers until the ball is steady in their grasp.

I think that people with very large hands will use less fingers for their all of their grasps, and will probably be able to grasp the basketball with one hand, because their hands are larger and their fingers cover a larger area of the object. I believe that people with very small hands will have more fingers to use for the maximum grasp, and also use more fingers for their preferred grasp. This will happen because their hands are smaller, and cover less area.

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