Metric biases in body and object size representations

The body is our primary interface with the world: it allows us to gather inputs from the outside, to build a representation of the world, to act and directly manipulate the environment. However, we do not perceive our body accurately. For example, in the absence of visual information, we distort our body by experiencing our hands as shorter and wider than their actual size and we misperceive the length and volume of our body segments. 

Do these distortions affect the way we perceive what surrounds us? From an ecological perspective, the selective misestimation of our body dimensions may affect our efficient interaction with the environment. We therefore aimed at studying whether the metric biases also extend to objects, and in particular to those that we interact with, or whether they are specific to the body. We used psychophysics and intracranial electrophysiological recordings (stereo-EEG) to investigate the perceived dimensions of the hand and several objects, and showed that metric biases indeed extend to objects. Critically, the pattern of distortions depends to a degree on the manipulability of the object, since objects which do not afford manipulation and interaction were differently represented. These studies contribute to our understanding of how we build our perception of our body and how we use it to bring about the world that we interact with.