5 ms·

I've always thought that humans don't perceive weight; instead, they perceive density.

vacri 10y ago
Carry a heavy load of shopping and you'll perceive weight, not density. It doesn't matter how big the bag is; what matters is that the handles are cutting into your fingers... ... or, for a more HN-friendly example, astronauts on the space station would not experience any difference in space to being on earth - objects in orbit have no weight, but do have density.
- dragonwriter 10y ago
  > Carry a heavy load of shopping and you'll perceive weight, not density. It doesn't matter how big the bag is; what matters is that the handles are cutting into your fingers... Pedantically, that's really pressure, not weight or density. (Though weight is a more direct contributor to pressure than density is.)
  - hsitz 10y ago
    Actually, pedantically, "weight" is a "force", so it makes perfect sense to say we perceive weight when we carry something. Our arms must provide an equal and counteracting force to sustain the weight of objects we carry. "The weight of an object is usually taken to be the force on the object due to gravity. . . . " https://en.wikipedia.org/wiki/Weight https://en.wikipedia.org/wiki/Weight
    - dragonwriter 10y ago
      > Actually, pedantically, "weight" is a "force", so it makes perfect sense to say we perceive weight when we carry something. Yes, but the "handles cutting into your fingers" is pressure not force.
      - hsitz 10y ago
        We're getting a little silly here, but I think it's both force and pressure. Any force will exert a corresponding pressure (which is merely "force per unit area"). To say that we don't feel the force of weight except as a pressure is getting overly pedantic; we don't generally think of carried objects as exerting a certain pressure on us, we think of them as being more or less "heavy", i.e., as having weight. Okay, the explanation for specific case of fingers being cut (while getting no cut in other cases) depends on the weight being applied to small area. . . :) But it is still perfectly true that the weight of the object cuts the fingers.
- hsitz 10y ago
  Are you suggesting that chimps would persist in trying to carry something that's too heavy for them, because they don't understand the concept of "weight", as tested for by some study? I haven't read the study, but I'm pretty skeptical about that. My thought is that, just as accounts of past decades have tended to place too much emphasis on avoiding anthropomorphism (i.e., imbuing animals with human traits), they have also erred, and probably continue to err, in the converse, thinking that human behavior is much more "rational" and "consciously controllable" than it actually is. In other words, animals are more like us than scientists thought forty or fifty years ago, and we also are more like them than previously thought (i.e., we are not as rational as we think).
radarsat1 10y ago
Actually what the illusion I linked to shows is that we "perceive" density by estimating it visually, and this can trump what our muscles and skin tell us about the weight of the object by means of pressure. So the answer is "both": we estimate density and weight, and what we perceive is a combination of the two, adjusted (biased) by our priors. Specifically, a larger object with the same actual density but the same visual appearance will feel "lighter" when compared. And it's a very strong illusion, in the sense that it works even if you know what's happening.. it's very hard to shake the feeling that the larger object is lighter even though they actually weigh the same.

vacri 10y ago

Carry a heavy load of shopping and you'll perceive weight, not density. It doesn't matter how big the bag is; what matters is that the handles are cutting into your fingers... ... or, for a more HN-friendly example, astronauts on the space station would not experience any difference in space to being on earth - objects in orbit have no weight, but do have density.

dragonwriter 10y ago
> Carry a heavy load of shopping and you'll perceive weight, not density. It doesn't matter how big the bag is; what matters is that the handles are cutting into your fingers... Pedantically, that's really pressure, not weight or density. (Though weight is a more direct contributor to pressure than density is.)
- hsitz 10y ago
  Actually, pedantically, "weight" is a "force", so it makes perfect sense to say we perceive weight when we carry something. Our arms must provide an equal and counteracting force to sustain the weight of objects we carry. "The weight of an object is usually taken to be the force on the object due to gravity. . . . " https://en.wikipedia.org/wiki/Weight https://en.wikipedia.org/wiki/Weight
  - dragonwriter 10y ago
    > Actually, pedantically, "weight" is a "force", so it makes perfect sense to say we perceive weight when we carry something. Yes, but the "handles cutting into your fingers" is pressure not force.
    - hsitz 10y ago
      We're getting a little silly here, but I think it's both force and pressure. Any force will exert a corresponding pressure (which is merely "force per unit area"). To say that we don't feel the force of weight except as a pressure is getting overly pedantic; we don't generally think of carried objects as exerting a certain pressure on us, we think of them as being more or less "heavy", i.e., as having weight. Okay, the explanation for specific case of fingers being cut (while getting no cut in other cases) depends on the weight being applied to small area. . . :) But it is still perfectly true that the weight of the object cuts the fingers.
hsitz 10y ago
Are you suggesting that chimps would persist in trying to carry something that's too heavy for them, because they don't understand the concept of "weight", as tested for by some study? I haven't read the study, but I'm pretty skeptical about that. My thought is that, just as accounts of past decades have tended to place too much emphasis on avoiding anthropomorphism (i.e., imbuing animals with human traits), they have also erred, and probably continue to err, in the converse, thinking that human behavior is much more "rational" and "consciously controllable" than it actually is. In other words, animals are more like us than scientists thought forty or fifty years ago, and we also are more like them than previously thought (i.e., we are not as rational as we think).

radarsat1 10y ago

Actually what the illusion I linked to shows is that we "perceive" density by estimating it visually, and this can trump what our muscles and skin tell us about the weight of the object by means of pressure. So the answer is "both": we estimate density and weight, and what we perceive is a combination of the two, adjusted (biased) by our priors. Specifically, a larger object with the same actual density but the same visual appearance will feel "lighter" when compared. And it's a very strong illusion, in the sense that it works even if you know what's happening.. it's very hard to shake the feeling that the larger object is lighter even though they actually weigh the same.