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see with your hands?

A new study at the Hebrew University shows that amputation of a hand causes a change in the vision of near space

Explanation of the way of seeing, in case of hand disability. Illustration: The Hebrew University
Explanation of the way of seeing, in case of hand disability. Illustration: The Hebrew University

We know exactly where a certain object is located when we say that it is "within our reach". But if we don't have a hand, can we still accurately identify the position of the object? According to a new study conducted at the Hebrew University, the answer to this is negative.

The space close to our body, where we can perform actions with our hands, such as holding and touching objects, is called the "action space". Studies show that the human brain encodes the visual information that appears in the near action space differently from the encoding of the information that appears in the far space, and therefore the brain representation of objects in the near action space depends on their distance from the hands. Now, a new study published in the journal Psychological Science shows that amputation causes distortions in visual perception and the ability to know where the object is located in the immediate space.

Neuroscientists Dr. Tamar Meikin, Mittal Wilf and Prof. Ehud Zahari from the Institute of Life Sciences at the Hebrew University, in collaboration with Dr. Isabella Schwartz from Hadassah Mount Scopus, explain in the article how hand amputation affects visual spatial perception. For the purpose of the study, 12 amputees were asked to observe a point in the center of the screen, when two squares were shown for a short time on either side of the central point. The volunteers were asked to determine which of the two squares was farther from the center.

Dr. Tamar Meikin, brain researcher, Hebrew University
Dr. Tamar Meikin, brain researcher, Hebrew University
Right-hand amputees tended to report that the squares were equidistant from the center even when the right square was shorter and further away. They estimated the distance on the right side as relatively small compared to the distance on the left side. In contrast, left-hand amputees reported that the two squares were located at an equal distance from the center when the left square was actually further away. However, when they repeated the task sitting far from the screen, no differences were found in the perception between the two groups - both left-hand and right-hand amputees estimated the distances more accurately. The results show that the amputation of the hand only affects the vision in the space close to the body.

"The findings show that the loss of the hand, which leads to the contraction of the action space, causes long-term distortions in spatial perception," says Dr. Meikin, whose research was carried out as part of her doctoral thesis. "The research shows that the possibilities for action in the near space shape our perception and that the ability to act in space affects the way it is perceived."

The results of the experiment have implications for the treatment of "side neglect" syndrome in the brain, a phenomenon in which a person has difficulty grasping information from one side, usually the left, following a brain injury. The syndrome is usually accompanied by paralysis of the hand on the affected side. The findings of the current study indicate that rehabilitation methods that focus on using the hands on the affected side may alleviate the symptoms of side neglect syndrome, by increasing the space of action on that side.

15 תגובות

  1. Year:
    Maybe I misinterpreted your intent but the reason why I interpreted things that way was that you decided to stand up for Yod on the subject that I didn't mean at all for the exact details of it but for the idea that it demonstrates. It seems to me almost like saying that my words are not accurate because there is a spelling mistake in them.
    In any case - regarding the information itself - it turns out that my mistake was bigger than I thought because as a ghost showed me in the same discussion - it turns out that all bats rested at a certain level of vision.

    Regarding color blindness - I repeat - the name of a phenomenon does not have to contain information.
    When someone says "the awl is out of the sack" he almost never means - neither the awl nor the sack. Is this a wrong expression?
    I repeat - there are no wrong definitions, and the Academy of Language or some other authorized body did not decide to call the phenomenon "pitching", I will continue to call it color blindness and so will all the others.
    More than that - the use of this expression will not confuse me and I will know exactly what is meant.

  2. Dear Michael
    I read the article about the bats and found there among the comments a reference to my response here6. I was surprised that you took my comment to what I considered inaccuracies to be an attack. Never. We're talking, aren't we? If my writing was too aggressive, I apologize.
    Regarding your response 11, the term color blindness carries false information, and is therefore a mistaken convention, unlike tomato, which is an ordinary noun whose hidden meanings are never re-examined by anyone in everyday speech. And the doctors are not blind and dumb, and are often wrong, for example in this matter.

  3. Thank you very much for the theology class. And back to the article - the question is whether they also checked people who have hands. Maybe all right-handed people (with and without hands) see the squares at equal distances (while standing at the same distance as in the first experiment)?

  4. And the religious connotations - I repeat - were only because you put religion in the same position as mathematics and the laws of nature.
    I cannot find enough words to express the magnitude of the error in this comparison.

  5. Year:
    Language is a matter of conventions and in this matter the phrase "wrong conventions" has no meaning.
    It is known that there are several types of color blindness and this does not make the expression untrue as it is known that there are many types of people and yet they are all human.
    I don't think there is any logic in trying to claim that the concept of "tomato" is incorrect because the concept of "correctness" is only valid for claims and not for definitions.
    Doctors call this phenomenon "color blindness" and this is what defines the term color blindness.

    Not true! The laws of mathematics and the laws of nature were not determined by humans. They were discovered by them. There is a huge difference.
    As I mentioned in my first response - those who try to "determine" the laws of nature do not survive because the laws of nature are stronger than their determinations.
    What is so hard to understand here?!
    There are things in reality that the person is not aware of and that goes without saying.
    After all, diseases of genetic origin existed even before we discovered the genes and people got cancer from excessive exposure to sunlight or from smoking before they found the connection between the things.
    After all, no one claimed that we know everything or feel all of reality with our senses, and in my first response I also said that there are animals that perceive reality differently.
    However - since the reality is one - there can be no contradiction between the different perceptions, only complementarity.
    Because humans are talented, they gradually build devices for them that expand their ability to perceive reality, therefore today humans are already able to experience in one way or another most of the things that the different animals can sense and of course many more things that the animals are unable to sense.
    I really don't understand what you are arguing about.

  6. Michael
    I did not understand the connection between my question and your response with the religious connotations.
    What I'm saying is that logic and mathematics and the laws of nature
    And the dynamic laws and the frozen laws you presented are all man-made laws
    And not for example by flying spaghetti or God.
    And all the laws that have been set and continue to be set are set by man. According to his perception and according to
    His calculations with the help of tools that were also first created in the mind of a person who preceded him.
    Your whole perception of reality (in whatever way you do it) is a perception of human reality,
    And you can't, for example, see like a bat sees and perceives reality. And if there is any
    An owl that can see X-rays and can see maybe some anti-particles or some Higgs boson
    And a person can't, so that doesn't mean that there isn't such a boson or such a particle or something that exists in nature
    But it does not exist in the human perception of reality because man does not 'perceive' it.
    In other words, how real is that reality that is based on human perception?

  7. Michael,
    Wherever the conventions are wrong, I have a special interest, which is why, among other things, I always respond when the phrase color blindness comes up.
    I once walked with a man, who by the bright light of an anemone said he saw her very pale. He was apparently, as he declared himself, blind to red.
    About half a percent or slightly more of men carry this phenomenon.
    About seven and a half percent of men have a completely different phenomenon. Confusion sometimes appears in their perception of red. They distinguish all colors and all their shades, as I briefly explained in a previous discussion (genetic therapy of color blindness).
    The "scientific" medical label "color blindness" is affixed to both groups. Regarding the second, larger group, this label is not just a mistaken convention,
    but completely false.
    Those who want to be precise should say confusion in the perception of red.
    Every time I am surprised anew to discover that the subjects of science and medicine and sometimes also mathematicians adhere to the usual conventions instead of preferring the study of reality that is given to some of them sometimes from first hand with clear proofs.

  8. Year:
    The purpose of your comment is not clear to me.
    I gave bats as an example and from the example you can understand that I meant those who do not see.
    I also didn't say anything about additional ways of sensing animals and if anything, their existence only emphasizes what I said. I did not intend to give here a complete lexicon of all the traits of all the animals and their characteristics but to illustrate certain ideas and that is exactly what I did.
    Regarding the color blind - I think the expression is excellent and I disagree with your words on the matter.
    The fact that it can be detected in a laboratory test is in itself proof of the difference between these people and others and that there are colors that do not distinguish between them.
    I responded to another aspect of your words right after your comment in the same article.

    There is a huge difference between the laws that I know from myself to be true and laws that are dictated to me by others.
    I don't learn the laws of mathematics and logic from anyone - I discover them myself and so does everyone who knows mathematics. It may be that a language and a name help me to find out, but I don't buy any law that I don't understand the deepest reasons for and that it is not clear to me that the fact that they helped me only shortened the path to understanding but did not make any substantial changes in it.
    There is also a huge difference between the laws of science that are obtained as a result of the application of logic and the results of experiments - laws that are the laws of nature - and sets of laws that are laws of behavior and that are not imposed by nature but constitute an agreement between humans.
    There is another difference (really irreconcilable) between a dynamic and adjustable system of rules of conduct that is based on the understanding of all humans in our time with all the latest knowledge and a system of rules of conduct established by primitive tribes thousands of years ago.

    It is possible to describe a whole scale in this regard, the distance between its two ends is enormous and much greater than the distance between east and west:
    "descriptive" laws
    1. The laws of logic and mathematics (the constants, inherent in us from birth and without which it is not possible to think at all)
    2. The laws of nature (which change as a result of the accumulated experience of the human race and as time passes - their description of reality without a doubt gets better and better)
    Rules of conduct:
    1. Dynamic laws that are updated over time according to man's understandings that improve as he gets to know the descriptive laws better
    2. Frozen laws of religions.

    A rational person's life is based on the first choice of the two categories.
    The life of a religious person is based on the second choice.
    The gap between the two traditions is, as mentioned, abysmal. I repeat it over and over again simply because I have no words to describe the disgust I feel in relation to the second approach and its comparison with the first.

  9. Michael
    After all, all the rules of physics, mathematics, philosophy, psychology, religion, whatever it is, were determined according to a perception of reality
    Humane. Neither dogs nor cats made the rules. Your perception of reality is also determined by you but you rely on it
    Also about those rules set by man and not just about how you interpret your senses.
    What does this mean about the true 'perception of reality'?

  10. Michael, I think there are some inaccuracies in your answer 3:
    As for bats, at least some species see.
    As for what the world looks like in the minds of animals, of course we cannot know, but we can do little about what they see and we cannot. For example, it was only recently published in a small section in the Haaretz supplement that falcons locate the small mammals they prey on by identifying the paths of their secretions that emit ultraviolet radiation. It is also accepted that many mammals do not distinguish colors, and there is quite a bit of additional knowledge about the visual properties of animals and humans.
    Regarding color blind people, I commented at on this topic. The expression despite its acceptability is not good to use because of its falsehood unless it is stated that it is half a percent of the people who are really color blind.

  11. Ghost:
    Not at all.
    When such proposals come up, I often suggest to those who really believe in it to try jumping from the Peace Tower and check if the laws of gravity are true or if they are just part of their perception of reality.
    Our logic was actually created in a process where billions of creatures were sacrificed who did just that - tried to act irrationally and wasted their lives.
    Those who survived those billions of attempts are those whose worldview is in high correlation with reality as it is.
    My perception of reality is not based on laws set by other people but on laws that I know from myself (thanks to evolution and thanks to experience) that they are true (as opposed to the religious laws that were really set by other people and some of which I know are not true).

  12. Michael
    Doesn't this mean that a human being's entire perception of reality, which is based not only on his senses but also on laws and rules previously established by other people, is only a part of tens of millions of different 'perceptions of reality' that exist for different animals?
    That is, the laws (of nature) established by man are not valid for the real and comprehensive reality, but only for man's perception of reality? (Although all animals share the same physical phenomena in nature but interpret them and react to them differently).

  13. Ghost:
    There is no practical way to know what the world looks like "through the mind's eye" of another animal.
    In fact, we cannot even know if it is perceived in the same way by all humans!
    Is my "red" experience the same as yours? There is no way to know that!
    The only way to examine another's (human or animal) perception of reality is by examining his reactions to it.
    We know that all those who are not color blind call red by the name "red". This is no proof that they perceive the color like we do, but only that they - like us - distinguish it from other colors.
    The experiments regarding animals' perception of reality are also carried out in a similar way.
    They are taught that they receive a reward for identifying an object (e.g. a ball) or a feature (e.g. green) and check if they actually recognize it.
    It is also clear that there are creatures who perceive the world in completely different ways and therefore their experience is different.
    Describe to you, for example, how a bat feels:
    His eyes see nothing but he gets an accurate picture of the structure of the environment through his ears!
    Is there anything strange about that?
    The truth is: certain (blind) people have learned to act like a bat and they orientate themselves in their surroundings (to the extent of using a skateboard in a parking lot and navigating between cars) by listening to the echo reflected from objects in their environment when they make clicking sounds with their fingers.
    In the latest issue of Odyssey there is an entire article on various forms of "sensory conversion" - a collection of methods that disabled people of various types learn to compensate for the loss of one sense by using another.

    More related to the article - it is clear that our perception of reality is affected by our ability to interact with this reality.
    It is not only about the hands but also about the use of tools.
    People who use a sword or a whip learn to recognize these objects as a kind of extension of their body and know how to use them to hit a fly.
    The same goes for those who drive a car.
    I assume that if and when amputees are fitted with artificial limbs - their perception of reality will return to normal.

    We, as humans, obviously have more tools to assess reality than animals because we know how to form an image also in objective ways that are less dependent on our senses. For example, if we are not sure that the distances on both sides are equal, we can use a measuring device and simply measure them.

  14. Does this research prove (in addition) that the human perception of space and the human perception of the world
    exists and valid only in the mind of man and not of any other animal? I mean, only humans see
    Nature as they see it and all the knowledge about nature known to man is only valid for man himself?
    Of course, other animals see nature in a relatively similar way (not 100%) to how they do
    Humans see nature, but it is impossible to know if, for example, a cat that sees a ball really sees the ball
    As humans see the ball.
    So I ask (if anyone knows, it must be Michael Rothschild, he knows a lot) does this research prove
    Or can prove a claim that in general all human perception of the world is valid only for humans? And in fact the world as it appears to humans appears that way only to humans and what the human sees is only a part of the world?

  15. Nice.. Now where will something arise that will decide that even amputees should be denied a license because they do not have a proper perception of space....

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