The way we understand what another person intends to do is naturally determined to a significant extent by context. For instance, we are less likely to be worried about the intentions of a man wielding a sharp scalpel provided he is wearing a white coat and is in a hospital operating theater. However, context does not provide the entire picture. Researchers had previously tested the idea that humans also use the intrinsic characteristics of motions to discern intention but the results were so far ambiguous.
To systematically determine whether observers are able to decode the intentions of others just by watching them, a team led by Cristina Becchio in the Department of Psychology at the University of Torino first recorded a group of participants reaching toward and grabbing a bottle of water and then asked observers to interpret their intentions. Some participants intended to pour the water into a glass while others intended to drink from it. The authors identified 16 individual kinematic parameters such as the height and velocity of the wrist as well as the movement of fingers, with which they could predict what the participants would do next. They then selected 100 individual grasping movements (50 with the intention to drink, 50 to pour) and showed them to the observers in a video recording. The observers correctly predicted whether the movement was performed with the aim of drinking or pouring more often than if this was purely by chance.
Becchio and her team found that the occurrence and timing of three specific features were the most important determinants for decoding intention: wrist height, its horizontal trajectory, and the vertical position of the back of the hand. When the authors tested the entire spectrum of movements on a further set of observers, they found that they also used these determinants to determine intention. This indicates that humans generally use these specific determinants to predict the intention of others. When the researchers showed the participants movements that should be particularly easy to predict based on these features, the observers were indeed better at predicting intentions.
What might be the neurological basis for this ability? During the execution of actions, neurons governing a specific motor action are linked in a chain with neurons responsible for the subsequent action. Becchio and her co-authors propose that a similar linking of neurons may be the underlying mechanism explaining how kinematic information can be so readily used to decode intention.
Written by Neysan Donnelly for AcademiaNet(© AcademiaNet)