Abstract
Concentric and eccentric contractions show different patterns of neural
activity at both peripheral and cortical levels, which are thought to
influence the perception of action properties such as the weight of
objects moved by others. The aim of this study was to investigate how
the type of muscle contraction influences weight estimation during
action observation.
Forty-eight volunteers completed the Main experiment and the Control
experiment. In the Main experiment, they performed a weight
discrimination video task in which they watched videos of an actor
moving two objects, a comparison and a reference box, executing
concentric or eccentric contractions and they had to indicate which box
was the heaviest. Sensitivity analysis and psychometric functions were
used to analyze the data. In the Control experiment, observers judged
the actor’s effort in moving the boxes.
The results of the Main experiment showed that the weight discrimination
sensitivity was higher in the Eccentric condition for the Light boxes.
Conversely, for the heaviest boxes, discrimination sensitivity was
higher in the Concentric than in the Eccentric condition. These results
were confirmed by the psychometric function analysis. The Control
experiment showed that for Light stimuli, the perceived difference in
effort between the comparison and reference stimuli was greater in the
Eccentric than in the Concentric condition.
These results showed that the ability to evaluate the weight of the
object involved in the observed action was influenced by the type of
contraction and the amount of weight. The effort attributed to the actor
influenced the observer’s perception.