Summary: Research reveals that how we perceive the size and weight of body elements, such as fingers, varies from our view of things. For things, smaller products feel heavier than larger ones with the same weight—a trend known as the size-weight idea.
However, this study found the same effect for brain elements: a smaller side feels lighter, and a larger hands feels heavier, despite their true pounds being constant. This finding reveals different ways that body parts and objects are perceived as weights.
The researches may help us better understand how figure errors manifest in conditions like eating disorders like anorexia nervosa. Experts suggest expanding these perceptions to advise treatments for conditions relating to body image.
Important Information:
- Opposite Illusions: The size-weight idea applies separately to objects and system parts, with brain size changes altering perceived fat in the same direction.
- Different Mechanisms: Weight understanding involves separate processes for objects and system parts, underscoring special brain functions.
- Clinical Relevance: By looking at how people perceive their own bodies, findings from this study may help develop therapies for eating disorders.
Origin: BIAL Foundation
Scientists have compared the belief of body parts ‘ size and weight, especially the hand, to the perception of things, and come to the conclusion that it is different.
In the case of things, the smaller we look at them, the heavier they seem to us, while in the case of arms, the result is exactly the opposite.
This study is crucial for understanding how people with eating disorders like anorexia nervosa practice their bodies ‘ size and weight.
According to Newton’s laws, weight is given by the solution of its size and inertia. How does the mental determine how much fat a body part or an object can hold?
It has been known for more than a century that how we perceive an object’s length affects how we feel about its weight. When we pick up a little thing and a large item with similar people, even when we push them, the smaller thing feels heavier ( for instance, a golf ball versus a beach ball ).
The size-weight illusion is a clear example of how a person’s perception of size has a significant impact on their perception of weight.
Little is known, however, whether the same is also true for the weight of parts of our body. With the support of the , BIAL Foundation, a team of researchers from , Birkbeck University of London , sought to answer this question by assessing the effects of embodying an enlarged hand and a shrunken hand on perceived hand weight in a sample of 20 healthy participants.
” We used a visual-tactile illusion with magnifying and diminishing mirrors to manipulate hand size,” says researcher Elisa Raffaella Ferrè.
We then used a psychophysical matching test to determine whether a hand weight hung on a person’s wrist feels heavier or lighter than the hand’s actual weight.
The findings were presented in the article” Perceived hand weight and hand size” published in the scientific journal Cognition in January 2025. They showed that the participants ‘ tendencies were less accurate when expressing a larger hand and more often when expressing a smaller hand.
This study showed that the size-weight illusion, which occurs in the perception of objects, does not apply to body parts, as an enlarged hand felt heavier and not lighter, even though it weighs the same, and the reverse logic for the small hand.
Thus, the results demonstrate that body parts and body parts have two distinct weight perception mechanisms.
Elisa Rafaella Ferrè,” An investigation into how individuals with eating disorders experience the bodily size-weight illusion, as presented in this study, can advance our understanding of these disorders and their association with bodily distortions,” says Elisa Rafaella Ferrè.
About this news about neuroscience research and perception
Author: Sandra Pinto
Source: BIAL Foundation
Contact: Sandra Pinto – BIAL Foundation
Image: The image is credited to Neuroscience News
Original Research: Open access.
” Perceived hand weight and hand size” by Elisa Raffaella Ferrè et al. Cognition
Abstract
Perceived hand weight and hand size
Our perception of the weight of objects in our surroundings is influenced by the dimensions of our bodies and our body parts. Recently, it has been suggested that the perceived weight of the hand is dramatically underestimated.
However, little is known about how our body parts’ perceived size is influenced by our own weight perception.
We examined the impact of displaying an enlarged and shrunken hand on perceived hand weight.
We used magnifying and minifying mirrors to alter hand size to create a visual-tactile illusion. We then used a psychophysical matching test to determine whether a weight hanged on a person’s wrist feels heavier or lighter than their actual hand weight.
Our findings showed that when a person embodies a smaller hand, they tend to underestimate the weight of their hand more, and less so when a larger hand is in their hands. That is, the hand’s perceived size affects how much it is perceived to weigh.
Importantly, our findings demonstrate resistance to the size-weight illusion by showing that the perception of the weight of body parts is processed differently from the perception of object weight.
To understand how hand size affects hand weight, we recommend a model based on constant density.
